International Bryozoology Association - 11th Conference, 1998 - Abstracts


Beate Bader
Geologisch-Paläontologisches Institut der Universität Kiel
Olshausenstraße 40, 24098 Kiel, Germany

Living bryozoan communities and related BRYOMOL-sediments occur in temperate latitudes. Dynamics of the bryozoan-thickets of Cellaria sinuosa and C. fistulosa on carbonate production and carbonate accumulation were studied on the shelf off North Brittany, France. Dense Cellaria-thickets show a patch-like distribution on the outer shelf in 70-80 m water depth where strong currents prevail. The erect flexible bryozoan is anchored by a bundle of chitinous, tubular rootlets in the loose sediment or is cemented on pebbles. The Cellaria-thickets form a specific habitat that attracts numerous other species to live in. Stable oxygen isotope composition has been studied for the growth pattern of different C. sinuosa colonies collected on October 1994 and 1995. The oxygen isotopes are in equilibrium with the ambient seawater and show a marked seasonal variation reflecting seasonal water temperature changes. The oxygen isotopes further suggest that the bryozoan C. sinuosa is perenníal reveal a life span of at least 1.5 years. The growth rate of the single Cellaria-colony is of approximately 4-6 cm per year. These results prove that quantification of carbonate secretion in C. sinuosa is a good tool for calculating carbonate production within the thickets. Influence of strong tidal currents and storm waves on the sea bottom are the most important factors for mechanical destruction of the Cellaria-thickets. C. sinuosa is able to regenerate broken internodes or broken joints and has also the possibility of lateral branching the bryozoan can counteract the destruction and keep the colony alive. High carbonate production in the Cellaria-thickets does not result in the high concentration of the Cellaria skeletal grains in the shelf sediment of the study area. The storm wave-events are one of the factors that prevent sedimentation of bryozoan sands in the production centre. Therefore, only a small number of biogenic detritus from the local populations is found as parautochthonous sands.


David K. A. Barnes
Department of Zoology and Animal Ecology
University College Cork, Lee Maltings,
Cork, Ireland

The cheilostomatid bryozoans are an important component of Antarctic benthic communities occasionally even locally dominating faunal assemblages. The ecology of the encrusting members of this taxa have until recently remained unknown. Those species studied, describe here, far from undergoing lengthy periods of hibernation as traditionally thought, actively feed for most of the year. Growth of the encrusting species studied is very slow in comparison with those from lower latitudes. Encrusting cheilostomatids are one of the primary colonizing agents and, through the high frequency of catastrophic disturbance, one of the major space occupying phyla. They are also one of the most important colonizers of both hard and soft externas of other biota from the intertidal to deep shelf waters. The rate of community development is very slow. Cheilostomatid bryozoans are poor overgrowth competitors in Antarctic benthic assemblages, but unusually are ranked into clear hierarchies with distinct competitive dominants. They also show striking differences from low latitude community development patterns, in that assemblages studied illustrate clear successional sequences.


David K. A. Barnes
Department of Zoology and Animal Ecology
University College Cork, Lee Maltings
Cork, Ireland

Erect cheilostomatids dominate the bryozoan fauna of Signy Island (and probably the most Antarctic shelf locations) in terms of numbers and biomass below approximately 40 m depth. Three of the more common species are Isoeculiflustra tenuis, Nematoflustra flagellata and Himantozoum antarcticum which are typical flustrines with erect, flexible (lightly calcified) morphology. In contrast, to previous assumptions about Antarctic benthic suspension feeders, they are able to feed for most of the year by being highly efficient at low particle concentrations. I. tenuis grows continuously, despite the brief feeding pause, but the rigid heavily calcified species Cellarinella watersi ceases growth in winter causing annual skeletal growth checks. The maximum colony lifespans found were between about 26 and 10 years respectively. Generally the polypide lifespans of I. tenuis, N. flagellata and H. antarcticum are about nine months and four or five are produced giving zooids about four or five year lifespans. Larvae are brooded for about 10 months before summer release. Avicularia are important at keeping the active surfaces free from sedimentation and epibiosis during these extensive lifespans.


David K.A. Barnes
Department of Zoology and Animal Ecology
University College Cork, Lee Maltings, Cork, Ireland
William G. Sanderson
Countryside Council for Wales
Plas Penrhos, Ford Penrhos
Bangor, Gwynedd, Wales, LL57 2LQ, UK

Faunal colonisation is described from positively and negatively buoyant debris found at locations spanning a latitudinal range of 133.5°. Study locations were situated at island sites away from major human conurbations and from all the latitudinal zones between the Arctic and Antarctic regions. Recently cast-up material on the strand line, and, at some sites material from the shallow sublittoral were examined. This preliminary study of marine debris examines trends in the prevalence of colonisation on debris, the density of colonisation events, the area colonised, and composition of the epifauna with particular reference to the Bryozoa. Debris were found to consist primarily of plastics and wood (many of which were anthropogenic). At most latitudes Bryozoa were found to be one of the most important, if not the major epifaunal component present on buoyant debris. The proportion of the positively buoyant items colonised increased towards the Equator from a minima at each polar region. On positively buoyant debris, the average density of colonisation events and total space colonised by epifauna decreased significantly towards the poles but the bryozoan proportion of the colonisation events per unit area or proportion of space occupied did not show a significant trend in the present study. On negatively buoyant debris latitudinal patterns of colonisation differed from those on positively buoyant debris, but showed no significant trends in the present study although colonisation was greatest at the high (Antarctic) study site. Overall it is suggested that latitude is a substantial influence on the epifaunal colonisation of positively buoyant debris, possibly more so than other influences previously described. Additionally, the authors suggest that anthropogenic debris may have increased the rate at which species may raft to remote island sites: it is possible that this may have ecological consequences for native endemic faunas.


Philip E. Bock
Senior Lecturer in Geology, RMIT
Melbourne, 3000, Australia
Patricia L. Cook
Associate, Museum of Victoria
Melbourne, 3000, Australia

Very large colonies of species of the cheilostomatid genus Adeona are a significant part of the shelf fauna of Australia. Colonies are attached to solid objects, such as large rocks, by a robust system of calcified stem segments, constructed as segments of porous calcareous skeletal material, with intervening connections, which are a mass of cuticular tubes. These stems can be up to 80 mm in diameter, and several centimeters long, ramifying over the substrate surface with tens of terminating roots, cemented to the substrate. A series of samples from southwestern Australia shows that one common mode of early colony development commences with the larvae metamorphosing on sponges, or on the colonies of flexible erect bryozoans, such as catenicellids. This settlement may take place several centimeters above the sea-floor. The early colony growth from the ancestrula then takes places in two opposing directions - upward as a rigid bilaminar blade-shaped frond, and downward as articulated stems. The stems become progressively longer, and ramify, and ultimately extend beyond the zone of attachment of the host animal, which itself may be anchored to rock surface, or attached to a large sponge or ascidian. Continued growth of the stem-root system then proceeds to form a strong, but slightly flexible, support system, which then becomes independent of the original sponge or bryozoan support. With further expansion, an extremely strong stem results, enabling the development of large colony sizes seen in Adeona.


Daniel R. Brumbaugh
Department of Zoology, University of Texas-Austin
Austin, Texas 78712

Recent morphological and stratigraphic work on several cheilostome genera (Metrarabdotos, Stylopoma, and Schizoporella) has revealed complexes of cryptic species throughout the Caribbean region, as well as punctuated radiations of these taxa. In order to further explore the evolution of cheilostomes, I am sequencing two regions of the mitochondrial genome (16S rDNA and COI) of Stylopoma and Schizoporella species (Schizoporellidae) collected primarily from Florida, Puerto Rico, and Panama. I am also analyzing skeletal morphologies from these taxa so that the independent and combined phylogenetic utility of these molecular and morphological data sets can be assessed. Ultimately, the most robust phylogenies will be used to analyze the evolution of zooidal polymorphisms in these taxa. I will discuss preliminary phylogenetic results from the molecular data sets, comparing the usefulness of each locus for reconstructions.


María Cristina Orellana
Facultad de Ciencias, Universidad Católica de la Santísima Concepción.
Concepción, Chile
Patricio Manríquez
School of Biological Sciences, University of Wales
Bangor, UK

In the shallow rocky subtidal of central Chile, and elsewhere in temperate waters, crevices and boulder undersurface are dominated by colonies of encrusting bryozoans. The studies aiming at understanding the structuring processes of such assemblages have dealt with: overgrowth interactions, larval release patterns; larval energetic expenditure and behaviour, both during the free-swimming stage and during settlement; patch colonization within the bryozoan matrix, and survival of settlers. A highly significant proportion of colonies in such environments are in contact with conspecific, rather than with colonies of other species. However, when the space is shared by several species overgrowth interactions take place, but involving a small percentage of the total surface area of established colonies. The above suggests near to symmetrical competitive abilities within the species of the assemblage. This contrasts with the known information for tropical encrusting bryozoan-dominated cryptic environments. However, competitive asymmetry is present in contacts involving colonies with large differences in body size, or in experimentally induced contacts between species from different assemblages. All species in this assemblage produce lecithotrophic larvae which are released only during daytime. Light is the main factor inducing release, most larvae being produced between sunrise and midday. Laboratory studies on larval behaviour and observations in settlement tanks have shown that settlement occurs soon after release, and near to the place where the larvae are released. The above suggests a limited larval dispersal, probably enforced by the costs of delaying settlement, which impairs settlement probabilities and post-settlement growth rate. A tendency for gregarious settlement involving con-specific colonies is required to induce female and larval production. Therefore, bryozoan colonies in monospecific stands are likely to cross-fertilize, self-fertilization remains undemonstrated for simultaneous hermaphroditic colonies. Experimental studies on patch recolonization within the bryozoan matrix have shown that small patches (0.2 cm²) are re-colonized by budding from the neighbouring colonies, while larger ones (2 and 7 cm²) are re-colonized by a combination of budding from established colonies and growth of new colonies originated from larval settlement. Settlement location affects survival and future colonial performance. All the above factors contribute to explain the distribution patterns observed in this community.


Alan H. Cheetham
National Museum of Natural History, Smithsonian Institution,
Washington, D. C. 20560, USA
Jeremy B. C. Jackson,
Smithsonian Tropical Research Institute, P.O. Box 2072, Balboa, Republic of Panama

Major changes in species composition and colony growth forms of cheilostome bryozoan assemblages of the Caribbean and adjacent tropical American regions accompanied the rise and closure of the Central American isthmus from about 13 million years (m.y.) to 3 m.y. ago. More than 300 detailed stratigraphic collections from Miocene, Pliocene, and Pleistocene deposits, made during the past two decades by team efforts in the isthmian region (Panama Paleontology Project, PPP) and the Dominican Republic (Neogene Paleontology in the Northern Dominican Republic, DR), provide the first opportunity to document these changes quantitatively. Taken together, the two sets of collections span the interval from about 16 m. y. to 1 m. y. ago, and overlap by about 8 m.y. However, concentration of sampling in the earliest Pliocene and older in the DR and in the latest Miocene and younger in the PPP makes it difficult to distinguish temporal change from spatial differences. The nearly 300 cheilostome species in the two sets of collections divide almost exactly into living and extinct halves. Observed stratigraphic ranges average 3-4 m.y. long for both sets of species, and, depending on the statistical approach used, average true durations can be estimated to be 4-7 m.y. long, or 25% to 40% of the 16 m.y. interval sampled. The relatively short durations produce statistically robust vectors of temporal change in faunal composition within each region. For the fauna as a whole, however, temporal change is obscured by spatial differences between faunas of the central Caribbean (DR) and isthmian (PPP) regions, which greatly exceed that between cheilostome faunas of the Caribbean and Pacific sides of the isthmus. The oldest faunas are characterized by cheilostomes with the three major growth habits - encrusting, erect, and free-living - in approximately equal abundance, but accounting for 40%, 50%, and 10% of the species, respectively. In faunas younger than 5 m.y. old, species with erect colonies declined to 20% in numbers and 15% in abundance, so that these faunas are dominated in diversity by encrusting growth (60% of species) and in abundance by free-living species (50%). Patterns of occurrence, abundance, and diversity of erect and encrusting species follow the "hollow" distributions typical of many groups of organisms, in which species known from one to a few occurrences greatly outnumber those with many occurrences. In contrast, frequencies of free-living species are "flat," with approximately the same numbers of species having many and few occurrences. The most widely distributed and abundant species is the free-living Cupuladria biporosa, occurring in more than 60% of the collections from each area. Because of these differences in pattern, the adequacy with which species with different growth habits have been collected varies from excellent for free-living species to only fair for encrusting ones. Despite these sampling biases, the evidence suggests gradual and subtle change, unlike the more clearly episodic patterns in corals and mollusks in the tropical American Neogene.


Anthony G. Coates
Smithsonian Tropical Research Institute
Apartado 2072, Balboa
Republic of Panama

The plate tectonic history of the Central American isthmus is reviewed from the Late Jurassic to the Present. The modern isthmus grew from a central magmatic volcanic arc with flanking Neogene sedimentary basins formed at the junction of the trailing edge of the Caribbean Plate with either the Pacific Cocos or Nazca Plates. Neogene sedimentary fore-arc basins on the actively subducting Pacific side of the isthmus have thick turbidite sequences(›4000m) of relatively young age (3.5 - 1.7 Ma), complex stratigraphy due to small exotic terranes formed either from ophiolite or seamount assemblages scraping off (obduction) and accreting to the Caribbean Plate, and only sporadic abundant and diverse macrofaunas. By contrast, the Caribbean back-arc basins have relatively condensed (‹l000m from 8 - 1.7 Ma) undisturbed sequences with numerous diverse macrofaunal assemblages. The Burica Peninsula section will be described to exemplify a typical fore-arc basin with a thick turbidite sequence. Dramatic shallowing of this sequence demonstrates that the Mid America Trench rose from more than 2000m depth (Lower Burica Formation) to nearshore shallow water (Upper Burica and Armuelles Formation) which appears to be related to the subduction of a segment of the Cocos Ridge. Three back arc basins on the Caribbean coast demonstrate various aspects of the development of the isthmus in the Late Neogene and have been studied using detailed lithostratigraphy, planktic foraminiferal and nannofossil biostratigraphy integrated with paleomagnetism. The Limon Basin (Costa Rica) contains a shallowing upward sequence of siliciclastic sediments capped by the growth of important coral reef faunas, now some 40m above sealevel. Timing and rates of uplift will be calculated to show that this part of the isthmus is also driven by Cocos Ridge uplift but offset in time from the Pacific side by about 1 million years. The Bocas del Toro Basin contains the longest and richest sequence of sediments associated with the rise of the isthmus. Lower Miocene bathyal sediments identify the pre-isthmian tropical ocean, overlain by a complex of igneous and sedimentary volcanics and reefs that indicate the initiation of island arc volcanism around 15 Ma. Extinction of the arc at about 10 Ma. in Bocas del Toro and subsequent marine transgression has produced a richly fossiliferous sequence of marine shelf siliciclastics and reefs ranging in age from about 8 to 1.4 Ma. The Panama Canal Basin provides evidence for a 40-20 m deep richly fossiliferous Caribbean shelf sequence from about 11-8 Ma overlain by coarser cross bedded coquinoid volcaniclastic sand. Surprisingly, these sediments imply a strong jet of Pacific water pulsing across the isthmus at about 6 Ma at a high stand of sea level. The majority of the benthic foraminifera in this deposit are of Pacific provenance.


Silvia Cocito (l), Francesca Ferdeghini (1), Carla Morri (2) and C. Nike Blanchi (l)
(1) Marine Environment Research Centre, ENEA Santa Teresa, P 0 Box 316, I-19100
La Spezia (Italy)
(2) Institute of Zoology, University of Genoa, Via Balbi 5, I-16126
Genova (Italy)

Bryozoan reefs are known in the geological past, but in the Recent only it few examples of bryozoan buildups have been reported. Clearly, bryozoans abound among the cryptofauna of modern coral reefs and may even be important as binders or secondary constructors. Schizoporella errata is a common constituent of fouling communities in harbours of the Mediterranean Sea, where its colonies may form sizable buildups (up to 40 cm wide and more than 20 cm high). The species is particularly abundant in La Spezia region, where it typically thrives in shallow and rather eutrophic waters. Three different environments have been taken into account: the small resort harbour of Lerici; the large port- complex of La Spezia; and the Island of Tinetto, at the entrance of the Gulf of La Spezia. Schizoporella multilaminar incrustations exhibit two different morphologies: 1) thick and densely packed planar expansions with flat or pimply outer surface; 2) simple or anastomosed digitations, with open or closed tips, protruding from a loosely packed base. The first morphology mainly develops in exposed sites, the second in quiet environments. A diverse biota, comprised of several guilds, is associated to these buildups. Schizoporella is a binder/constructor that, being a superior competitor, overgrowths barnacles, mussels and serpulids (secondary constructors). Hydroids and algae (bafflers) settle on the outer surface of the buildups: their overgrowth by Schizoporella probably originates the funnel-like digitations. The basal parts of the bioconstruction, comprised of dead layers of the colony, are inhabited by boring bivalves and sipunculids (destroyers), whereas many vagile animals (dwellers) find shelter within the buildups.


Patricia L. Cook
Associate, Museum of Victoria
Melbourne, 3000, Australia
Philip E. Bock
Senior Lecturer in Geology, RMIT
Melbourne, 3000, Australia

Branches of the erect, traditionally "bicellariellid" species assigned to Dimetopia hirta MacGillivray, have been found to originate from the zooids of an encrusting phase which appears to be referable to the "calloporid" genus Retevirgula Brown. The primary zooids of the erect phase originate as elongated, hollow, helicoidally constructed "stalk" zooids arising from the marginal septular pores of the encrusting phase zooids. Only the erect phase produces ovicells. The remaining species of Dimetopia, including the type species, D. cornuta Busk do not appear to develop from an encrusting phase. The effect of the taxonomic identity of the two growth phases on the systematic relationships of the genera Dimetopia and Retevirgula is briefly discussed. Since the genus Dimetopia differs significantly from both Bugula and Bicellariella, the justification for incorporating these and other genera into the family Bugulidae is now less compelling.


Sean F. Craig
Dept. of Evolution & Ecology, Univ. of California at Davis
2310 Storer Hall, Davis, CA 95616
Kerstin Wasson
Department of Biology
University of Califomia at Santa Cruz
Santa Cruz, California 95064

Mechanism to distinguish self from conspecific non-self have evolved in an extraordinary range of marine invertebrates, including sponges, hydroids, corals, anemones, and ascidians. In contrast to contnuing work on the evolution of self/non-self recognition in the colonial marine hydroid Hydractinia symbiolongicarpus, and the colonial ascidian Botryllus schlosseri, relatively few studies have examined whether self/non-self recognition occurs in bryozoans, desspite frequent intraspecific contact among bryozoan colonies in numerous habitats. In this study we examine the outcome of intraspecific contacts among colonies of the cheilostome bryozoan Hippodiplosia insculpta grown on glass slides suspended from the dock at Friday Harbor Marine Laboratory (FHL) in Washington, USA. Separate colonies of this bryozoan were haphazardly collected from the intertidal zone on San Juan Island, and fragments containing approximately 50 zooids were obtained by breaking off a piece of the bilaminar growth which results when this species grows vertically off its algal substrate. These fragments were then tied with string onto glass slides in such a way that three pieces, each originating from a separate, physically distinct colony, were established on a single glass slide. Five such slides were then placed in a plastic slide rack cut open so that seawater could flow over the colonies on each slide. Four replicate slide racks (with a total of 20 glass slides containing 60 newly established Hippodiplosia fragments) were hung off the FHL dock and allowed to grow for three months. All slides were then cleaned and dried to allow observations with light and scanning electron microscopes. The growth of Hippodiplosia on these glass slides frequently resulted in extensions of a colony off the surface, producing an upright wall. Remarkably, the vast majority (52/56 or 93%) of upright growths formed by zooids from a single colony resulted in "walls" in which zooids were perfectly matched on either side (e.g. growing in unison). This synchrony of upward growth in bilaminar folds was true even in walls which were growing at an oblique angle. In contrast, upward "wall" production resulting from the collision and vertical growth of two separate colonies was rarely "synchronized"; hence the upward growth of one colony was not matched by that of zooids from the other colony the other side. In addition, overgrowth often occurred in other areas of contact between distinct colonies. Nevertheless, 6 out of 27 inter-colony contacts (22%) resulted in fusion, where upward growth was fully "synchronized" between colonies. Cases of fusion also contained "coalescent" zooids, apparently resulting from tissue budded by both colonies, in areas of where zooidal growth converged. In conclusion, it appears that colonies of Hippodiplosia insculpta do distinguish between self and non-self, and aspects of both zooidal morphology and growth form can be used to discriminate between these behaviors.


Jean-Loup d'Hondt
Laboratoire de Biologie des lnvertébrés Marins et Malacologie,
Museum National d'Histoire Naturelle
57, rue Cuvier, F-75231 Paris Cedex 05

One hundred and fifty plates of the Lamouroux's herbarium have been recently rediscovered in the building of the botanical garden of the Caen University, mixed with the Lenormand's and Chauvin's collections; then, they have been transferred in the Paris National Museum of Natural History. The study of this material allowed to identify the type-specimens, presumed lost, of twenty-five species of cheilostomatous Bryozoa, described by Jean-François-Félix Lamouroux in 1816 and 1824. These species have been redescribed with other scientific names by some more recent authors; so the generic and specific names given by Lamouroux are senior synonyms; the synonymies are here discussed. This paper completes the critical list of the rediscovered type specimens of Lamouroux published in a previous work (d'Hondt, 1993) and re-establishes several taxonomical priorities.


Matthew H. Dick, Lucas P. Williams, and Mishael Coggeshall-Burr
Department of Biology, Middlebury College
Middlebury, Vermont 05753 USA

The existing higher-level classification of gymnolaemate bryozoans contains many nominal taxa which are not natural, or monophyletic, groups. This classification, based largely on grades of organization, serves as a useful and necessary template for organizing knowledge. However, an understanding of sister-group relationships is crucial to an understanding of bryozoan evolution, and will hopefully eventually be reflected in gymnolaemate classification. Discernment of gymnolaemate sister-group relationships using morphological characters has been hampered by high degrees of homoplasy. Molecular sequences provide an alternative source of data for this purpose. Using "universal" primers 16Sar and 16Sbr, we have amplified and sequenced an approximately 500 bp stretch of 16S (large subunit) mitochondrial ribosomal DNA from 20 bryozoan species representative of a number of higher gymnolaemate taxa: four ctenostomes (genera Alcyonidium, Farrella, Flustrellidra, and Sundanella), seven anascans (genera Antropora, Bugula, Cellaria, Discoporella, Electra, Scrupocellaria and Thalamoporella), seven ascophorans (genera Celleporaria, Celleporella, Celleporina, Microporella, Phidolopora, Schizomavella, and Schizoporella), and two cribrimorphs (genera Cribrilina and Reginella). The selection of taxa was to some extent determined by availability of living or alcohol-preserved material relatively free of epibionts and in sufficient quantity and condition for DNA extraction. Our goals were to assess the taxonomic level at which this 16S fragment was likely to be informative for phylogeny reconstruction, and to determine phylogenetic relationships among the cheilostome taxa mentioned above. It was necessary to include ctenostomes, both as outgroups and to begin to address the possibility of cheilostome polyphyly. Sequence alignment and analyses are underway to incorporate recently sequenced taxa. Previous analyses with fewer taxa, and preliminary analyses with the current data set, show a monophyletic group containing the ascophorans Celleporaria, Celleporina, Microporella, Phidolopora, Schizomavella, and Schizoporella. They are separate from a clade containing the ascophoran Celleporella, which groups with the anascans Antropora, Scrupocellaria, and Cellaria and cribrimorph taxa. This provides support for the view that at least some of the different modes of frontal wall formation in ascophorans had independent origins, and thus that ascophorans are a polyphyletic group.


Yasser A. El Safori
Ain Shams University, Faculty of Science,
Geology Department Cairo-Egypt

The middle Eocene bryozoans of Egypt are separated into three main acme horizons, two horizons in Lutetian and one horizon in Bartonian. Bryozoans distribution increases with time. The last acme horizon is geographically the widest. It is modeled according to the bryozoans distribution, diversity and zoarial growth-form. In the presented model, the bryozoan paleoenvironments are separated into eight bryozoan terrains. Each terrain is characterized by its specific bathymetry, water turbulences and rate of sedimentation. Also, the presented model helps in constructing a detailed paleogeographic map for the late middle Eocene of Egypt.


Yasser A. El Safori
Ain Shams University, Faculty of Science,
Geology Department

The bryozoans extracted from the lower part of the Esna Shale in the Farafra Oasis express a first record from the early Eocene of Egypt. Fifteen species have been recorded, encrusting and erect flexible growth-forms mostly represented by cyclostomatous and anascan bryozoans are dominant. Among the studied assemblage, seven species are believed to be new. Paleoecological interpretation revealed the recognition of the erect rigid growth-form common in the middle and upper Eocene, however rarely. Shallow depth, low rate of sedimentation and moderately turbulent waters characterize the unique reefal development in the Esna Shale.


Helena Fortunato
Smithsonian Tropical Research Institute,
Center for Tropical Paleoecology and Archaeology
Box 2072, Balboa, Republic of Panama
Budd, A.F., Foster, C.T., Jr., Golden, J.
Department of Geology, University of Iowa,
Iowa City, IA 52242.

The reliability of any survey of biodiversity through geologic time depends heavily on the consistent identification of taxa. Comparisons with well-illustrated syntheses of taxonomic and distributional information are an essential component in the process. The application of WorldWide Web technology is illustrated by a new biotic database, entitled Neogene Marine Biota of Tropical America ('NMITA') (, which currently includes data on bryozoans, corals, molluscs, and ostracodes. NMITA contains high-quality images and synoptic information on taxa collected as part of two large multi-taxa fossil sampling programs designed to document changes in marine biodiversity in tropical America over the past 20 million years: (1) the Panama Paleontology Project (PPP) of the Smithsonian Tropical Research Institute in Panama and (2) the Dominican Republic (DR) project of the Natural History Museum in Basel, Switzerland. NMITA is the first image-based computer system documenting identifications made of an entire bryozoan fauna. It provides high-quality SEM images and data for approximately 200 of the more than 300 bryozoan species known from the Neogene of tropical America. Almost one-third of the species are formally undescribed. By selecting the name of a species from a taxon list, users may obtain images of representative specimens of the species and information on its authorship and spatial and temporal distribution. The taxon list may consist of an all-inclusive systematic inventory, or it may be generated using various search tools involving data on geographic location, stratigraphic position, and geologic age. Eventually images will be available for all taxa, and search tools using diagnostic morphologic characters will be designed for the infraorder Umbonulomorpha, family Schizoporellidae, and superfamily Microporoidea. A CD-ROM will be provided with the conference proceedings.


Dennis Gordon
National Institute of Water & Atmospheric Research
P.O. Box 14-901 Kilbirnie
Wellington, New Zealand

With c. 980 genus-rank taxa currently recognized (excluding synonyms), the Jurassic-Recent order Cheilostomatida offers a challenge to classification and the unraveling of phylogenies. Although compelling evidence exists that the stem group of the earliest cheilostomes includes Jurassic arachnidiids (order Ctenostomatida), the monophyly of both the order and most suprafamilial taxa has been questioned. While it can be argued that most non-malacostegan, anascan-grade cheilostomes are derivable from the paraphyletic Calloporidae, there is far less consensus concerning the ancestors of the suborder Ascophorina. In this paper, nine morphological models are presented to account for the origination of the range of ascophorine frontal-shield types that exist. These are:

  1. the calloporid origin of the cribrimorph costal shield;
  2. the cribrimorph origin of the gymnocystal shield and ascus;
  3. the kenozooidal origin of double-shielded Platyglenidae and Bifaxariidae;
  4. the kenozooidal origin of umbonuloid shields;
  5. the costal origin of the umbonuloid shield;
  6. the costal origin of the frontal shield in Bellulopora;
  7. the calloporid origin of Chorizopora;
  8. the cryptocystal origin of the pseudoporous lepralioid shield; and
  9. the multiple umbonuloid origin of lepralioid shield.
Each is evaluated on the basis of evidence from the fossil record and the occurrences of mixed shield morphologies in some taxa. Models 1-4, 6, and 9 are favored; models 5 and 7 are equivocal. The ascophorine ascus (compensation sac) is an invagination of the membranous frontal wall, wether from the vicinity of the proximal orificial rim or as a proximal extension to the costal- or umbonuloid-shielded areas when these are reduced and/or lost. The ascus sac is homologous throughout, and its floor may be regarded as a topological continuity of the membranous frontal wall, even if the membranous roof of the sac becomes developmentally separated from the frontal epitheca and retreats proximally under the frontal shield in some taxa. The paraphyletic cribrimorphs, in which an invaginated ascus first occurs, are regarded as directly or indirectly ancestral to the bulk of the Cheilostomatida, which are therefore largely monophyletic. The umbonulomorphs are also paraphyletic, and the hippothoomorphs and lepraliomorphs polyphyletic. A cladistic analysis of 92 genera using 103 characters yielded a cladogram that mostly resembles traditional classification, rather than the relationships suggested in those models that involve transformation of characters.


Steven H. Hageman and Scott Lidgard
Department of Geology
Field Museum of Natural History
Roosevelt Rd. at Lake Shore Drive
Chicago, Illinois, 60605, USA

How many times have we tried to list some attribute of a taxon or a fauna, or asked a simple question relating places, ages, environments, and references, only to be frustrated by the dispersed and sometimes obscure bryozoan literature that contains the answer? We have conceived the bryozoa data exchange as a literature and collection database in which four primary tables - Taxa, Localities, References, and Growth Habit, are linked together by a fifth table. Occurrences, that contains numeric keys relating all the unique occurrences of each species name in the database to information on higher taxonomy, synonymies, geographic and stratigraphic occurrences, geologic timescales, and standardized references. The current version of the database contains over 22,000 Cheilostomate and Cyclostomate Bryozoa. While still in development, the database allows independent and relational queries on all data fields, and is intended to accommodate all living and fossil bryozoan taxa. It is a prototype for an internet based server, with links to a geographic information system (ArcView) and plate tectonic reconstructions (Paleomap). We welcome your contributions, criticisms, and suggestions.


Eckart Håkansson
Geological Institute, University of Copenhagen,
Oster Voldgade 10, DK-1350 Copenhagen Denmark

Lunulite cheilostomes pose a very complex biogeographic pattern combining strongly changing global diversity through time with very distinct shifts in geographic distribution. Thus, in the latest Cretaceous of NW Europe they experienced an all-time diversity high, while the rest of the World has yielded just over a handful of species of comparable age; in the Late Eocene they reached their second diversity high with a prominent stronghold in North America, albeit a fair amount of contemporaneous species have been recorded from most of the rest of the World; and, finally, in Recent faunas they are a prolific endemic element in the shelf seas of Australia and New Zealand. The complexity of this biogeographic pattern naturally raises the question as to what extent lunulite history involves migration as opposed to independent, local evolution of free-living clades of lunulite body plan. Unravelling this puzzle requires insight into the nature and composition of intermediate lunulite faunas - both in terms of age and geography. Recent investigations already indicate that very few lunulite species may have survived the Cretaceous-Tertiary boundary into the Danian, and possibly none of the survivors lived through the Paleocene. Hence the Eocene high in lunulite history was possibly derived entirely from lunulite clades evolved independently during the early part of the Paleogene. In view of this possibility the predominantly Neogene lunulite history of Australasia should also be reconsidered. Rich bryozoan faunas from the late Paleocene of the Carnarvon Basin, Western Australia comprise the oldest lunulite cheilostomes thus far known from the Australasian biogeographic realm. In view of the peculiarities in lunulite biogeography outlined above, these faunas are of particular importance in two respects: 1) they are intermediate in age in relation to the diversity highs in the overall phylogeny of the lunulites, and 2) they may throw light on the roots of the Australasian branch of the lunulite tree.


Jean-Georges Harmelin
Centre d'Océanologie de Marseille, DIMAR
CNRS, Université de la Méditerranée
Station Marine d'Endoume, 13007 Marseille, France

Submarine caves and smaller cavities shelter a large part of the bryozoan fauna occurring in the coastal zone. These semi-closed habitats are subjected to strong environmental gradients (light, water circulation, space and food resources, temperature) channeled from the photic zone to the innermost dark recesses. This pattern leads to marked zonation of sessile assemblages shaped by exclusion/selection of growth-forms, individual sizes, feeding habits, and life-histories. Bryozoans show a contrasted taxonomical and numerical success along the cave gradient. In situations close to the cave entrance where food is not limiting and competitive interactions for space are predominant, the bryozoan fauna is moderately diverse and abundant, comprising large-sized species well adapted to interference competition. Intermediate inner situations allow encrusting bryozoans to form aggregations which show a great between-site variability, and which may monopolize space. In remote recesses, increased water stagnation results in a considerable drop in bryozoan abundance (number of colonies, cover) in spite of reduced space competition. Modest consumers able to exploit scarce food resources trapped into the boundary layer are favored while more energy-demanding organisms such as large-sized ascophoran bryozoans are excluded. Selection of small encrusting colonies with early reproduction suggests adaptation to very low levels of food inputs supplied by sporadic pulses. The wide range of size and origin of the cryptic habitats occurring in the coastal zone allows to examine the respective effects of habitat fragmentation and age on resident assemblages. Colonization experiments on substrates deposited along the cave gradient indicate that the recruitment features (origin, diversity and abundance of recruits) are dependent on- patterns of the local water circulation. Colonization rate in inner stations is surprisingly low, suggesting that production and dispersal of larvae from resident colonies are very low and that imports from outside communities are limited to the cave areas close to the entrance. In spite of many faunal similarities between dark caves and habitats from the continental slope, cross-shelf imports of propagules from deep-water habitats towards caves appear to be very unlikely, even when hydrographic conditions may favor them.


G. Hillmer & E. Voigt
Department of Geology and Paleontology. University of Hamburg,
Bundesstrasse 55, D-20146
Hamburg, Germany, Tel, 49 40 4123 5040. Fax 49 40 4123 5007,

In 1921 and 1922, E. Voigt (Hamburg) sampled the Upper Cretaceous (lower Santonian) bryozoan-beds of the region south of Hannover, NW-Germany (Voigt 1924, 1929). The outcrops do not exist anymore, and most of the personal notes of E. Voigt on the circumstances of collection were lost during the war (1943). The samples "survived' in part and details of the overall facies had to be reconstructed from the memory of E. Voigt (1997). The benthic community of the Santonian from NW-Germany (locality: Groß-Buelten). One of the most characteristic species was 'Lichenopora ' suecia which produced small bryostromatolitic reefs in a soft-bottom environment, (B, C=fungiform bryozoans; L="Lichenopora"; V= Volviflustrellaria ). For cyclostome Bryozoa from the middle Santonian beds which were previously assigned to Fasciculipora (F. hustedti and F. constricta) the new genera Bueltenopora n.g. and Constrictopora n.g. are proposed. Both genera are characteristic for the regional coastal facies, but do occur also in the Campanian of Scania (Sweden). Their robust mushroom-shaped (fungiform; pedunculate) zoarial morphology is probably ecomorphic. Main control factors are due to hydrodynamic effects at the sea bottom. The fungiform bryozoans are very common in the transition beds between the underling conglomeratic ironstone ore. These are covered by mainly calcareous sediments.
Voigt, E. (1924). Beitrag zur Kenntnis der Bryozoenfauna der subherzynen Kreidemulde. - Paläont. Z. VI/2: 93247.
Voigt, E. (1929). Die Lithogenese der Flach-und Tiefwassersedimente des jüngeren Oberkreidemceres. -Jb. Hall. Verb. Z. Erforsch. D. mitteldeutsch. Bodenschätze, N.F. 8:1-138, Taf. 1-13. 5 Abb. Halle


Alan S. Horowitz
Department of Geological Sciences, Indiana University
Bloomington, Indiana 47405
Joseph F. Pachut
Department of Geology, Indiana University-Purdue University at Indianapolis
Indianapolis, Indiana 46202

A listing and database of fossil bryozoan species presently contains more than 16,350 proposed names. Eliminating replaced junior homonyms and many proposed subjective junior synonyms reduces the number of names to approximately 14,250, which represents a 13% reduction. The pattern of fossil bryozoan species diversity is the same as for the bryozoan data sampled by Raup (1976) from 70 years of the Zoological Record as well as similar to the pattern of diversity in higher level invertebrate taxa summarized in Sepkoski (1993). No pre-Ordovician bryozoan species are presently recognized. Paleozoic bryozoans are part of Sepkoski's Paleozoic fauna, which expands dramatically through the Ordovician and appears to have reached a diversity plateau through the remainder of the Paleozoic except when perturbed by major extinction events, the causes of which are still the subject of debate. No bryozoan species and only a few genera are known to have survived the end-Permian extinction. The Paleozoic survivors did not survive the Triassic. Bryozoans staged a slow increase from a very low level of species diversity in the Triassic until the increase of cheilostome bryozoan species, especially in the late Cretaceous. In contrast to the end-Permian extinction, more than 180 species are reported to have survived the end-Cretaceous extinction. Late Cretaceous and Cenozoic standing species diversity may have exceeded that of the Paleozoic, following an empirical pattern that may represent the continued subdivision of ecologic space or may represent better collecting conditions in younger rocks and the general pull of the Recent. In any event, fossil diversity is always less than modem bryozoan diversity and on a names/million years basis is an order of magnitude lower. Although results for the 1990's are incomplete, creation of new fossil taxa has generally decreased since 1950.


Jeremy B. C. Jackson
Amalia Herrera C.
Center for Tropical Paleoecology and Archeology
Smithsonian Tropical Research Institute
Box 2072, Balboa, Republic of Panama

Zooid and ovicell size of cheilostomes vary considerably among environments. Zooid size is correlated with diet, growth rate and ecological dominance among species, and may increase within species with decreasing temperature. Ovicell size is correlated with clutch size, larval size, and larval and post-larval survival; all of which are important components of cheilostome life histories and are in turn correlated with ecological attributes associated with zooid size. If these variations are adaptive, we would expect zooid and ovicell size of entire faunas to vary predictably across environmental gradients in primary productivity, seasonality, availability of different substrata, or other factors. Alternatively, size could be constrained historically or phylogenetically, so that it is also necessary to compare groups of closely related species as well as entire faunas. Finally, ovicell size may be functionally constrained by zooid size, or the two parameters may vary independently. We tested these different alternatives using measurements for 42 species from the Gulfs of Chiriqui and Panama on the eastern Pacific coast of Panama and for 45 species from the San Blas Islands on the Caribbean coast of Panama and from Jamaica. The eastern Pacific is highly seasonal with high primary production, although less so in the Gulf of Chiriqui than the Gulf of Panama. In contrast, the Caribbean regions exhibit little seasonal variation and are oligotrophic. Both zooid size and ovicell size are significantly different among the four regions, but the only significant pairwise comparisons are between the Caribbean and eastern Pacific, and not within either ocean. Lack of differences between the Gulfs of Panama and Chiriqui, which have two thirds of their species in common, suggests that intraspecific variation in response to environmental differences is limited and that paleoecological interpretations based on size should be made with caution. We next combined all the data from each ocean for transisthmian comparisons. Both zooid and ovicell size are significantly larger in the Caribbean than the eastern Pacific, even though the eastern Pacific is seasonally much cooler than the Caribbean. These differences reflect differences in both mean and median size, and hold for comparisons of congeneric species across the Isthmus as well as for entire faunas. Moreover, size-frequency distributions are unimodal in the eastern Pacific but bimodal in the Caribbean. The bimodal distributions result from 16 Caribbean species with much larger zooids or ovicells than observed from the eastern Pacific. These differences across the Isthmus parallel those for echinoderms, reef-building corals and strombinid gastropods; which strongly suggests a common adaptive explanation. Lastly, zooid size and ovicell size are not consistently positively correlated, which suggests that there is considerable scope for independent or opposite selection on zooid and ovicell size


Kimberly E. Jones
Terrence G. Marsh
Department of Biology, North Central College
PO Box 3063, Naperville, IL 60566-7063, USA
Timothy S. Wood
Department of Biological Sciences, Wright State University
Dayton, OH 45435, USA

Traditionally, colony collecting has been the primary method for establishing distribution patterns of phylactolaemate bryozoans. Often, however, colonies are not present due to seasonally changing environmental conditions. To help detect species present at a lentic site during a survey, we developed a sieving technique that isolates both the large and small statoblasts of freshwater bryozoans. Since statoblast morphology is species specific, we can use them to establish more complete distribution information. We collect statoblasts by washing a bottom sediment or shore drift sample through a stack of standard sieves with mesh openings of 1.0 mm, 500 µm, and 150 µm. The 1.0 mm sieve separates large material from the sample; the 500 µm sieve isolates the large statoblasts from the small statoblasts which collect on the 150 um mesh sieve. By sieving, we found the characteristic large statoblasts of Pectinatella magnifica in 37% of 38 Illinois lakes. In comparison, when searching only for colonies, we found P. magnifica at only 21% of 135 lentic sites. Also, for the first time in Illinois, Wood and Marsh (1996) used sieves to detect the large statoblasts of Lophopodella carteri, at two of these 135 sites, while we only discovered this species once in the state by finding colonies first. Furthermore, by sieving, we found evidence that Plumatella nitens, which produces small statoblasts, occurs in 63% of 49 southeastern Wisconsin glacial lakes. Considering the abundant and consistent presence of statoblasts in nature, we propose that the method we describe will produce more reliable distribution data than colony collection alone.


Marcus M. Key, Jr.
Department of Geology, P.O. Box 1773, Dickinson College
Carlisle, Pennsylvania 17013-2896, USA (e-mail:
William B. Jeffries
Department of Biology, P.O. Box 1773, Dickinson College
Carlisle, Pennsylvania 17013-2996, USA (e-mail:
Harold K. Voris
Division of Amphibians and Reptiles, Roosevelt Road at Lake Shore Drive
Field Museum of Natural History, Chicago, Illinois 60605, USA
Chang M. Yang
Department of Zoology, National University of Singapore, Kent Ridge
Singapore 0511, Republic of Singapore (e-mail:

Bryozoans are common fouling organisms on sessile, inorganic, hard substrates. They are also known as epizoans on a variety of living substrates including both nektonic and motile benthic hosts. Epizoic bryozoans are less common on motile ephemeral substrates where the host regularly discards its outer surface. Two cheilostome bryozoans, Biflustra (Membranipora) savartii (Audouin) and Electra angulata (Levinsen), are reported on 56 specimens of the horseshoe crab, Tachypleus gigas (Müller), from the seas adjacent to Singapore. This study attempts to quantify the relationships between the number, size, and spatial distribution of epizoic bryozoan colonies and the size, gender, behavior, and morphology of the hosts. A total of 376 bryozoan colonies were found on 43 fouled horseshoe crabs. Compared to female horseshoe crabs, the males had more and larger bryozoan colonies as well as more total and percent cover by bryozoans. What makes these gender differences so dramatic is that the females had much larger surface areas than the males. Other factors affecting these patterns include the host's molting frequency and environmental preferences. More and larger epizoic bryozoan colonies grew on the dorsal surface as well as on the opisthosoma of the horseshoe crabs than on the ventral surface, prosoma, telson, or on the walking legs. As expected, the spatial distribution of epizoic bryozoan colonies on the host horseshoe crabs was bilaterally symmetrical. These bryozoan settlement patterns may reflect pre-settlement larval choice or post-settlement differential mortality. Bryozoans on these horseshoe crabs may experience post settlement mortality due to subaerial exposure and abrasion from copulation and burrowing. Understanding the spatial distribution of bryozoans on extant hosts, will permit more effective evaluation of similar patterns on extinct hosts in the fossil record. One of the problems with studying biofouling in the fossil record is that it is hard to determine which epizoans settled on their host before and after the host died. By studying these patterns on living hosts, it is hoped that these patterns can be distinguished.


Nicholas Larsen & Eckart Håkansson
Geological Institute, University of Copenhagen,
Oster Voldgade 10, DK-1350 Copenhagen, Denmark

The chalk in Denmark documents the closing of the Cretaceous period as well as the termination of more than 25 Ma of continuous chalk deposition. The stable depositional environment during the later part of the Cretaceous gradually allowed a specialized benthic fauna of exceptionally high diversity to colonize the soft chalk sea bottom, and in the latest Maastrichtian this diversity reached its maximum in the bryozoan mounds at Stevns Klint, Denmark. The mounds are asymmetrical with relatively steep SE flanks and more gently sloping NW flanks; their length is approximately 35 m and the topographic relief is up to one meter. From one such mound, 24 samples were investigated for their faunal composition. The benthic fauna is heavily dominated by bryozoans (about 85%), indicating that the growth of the bryozoans was instrumental in mound formation, in all probability determined by a unidirectional bottom current as suggested for the overlying Lower Danian bryozoan limestone mounds by Thomsen (1976, 1983). Pronounced variation in distribution and composition of the benthic fauna, suggest that the depositional environment varied considerably over each mound. Thus, it appears that the ordinary chalk benthos, which constitutes the traditional, non-predictable benthic community of level bottom Maastrichtian chalk, is re-distributed into a dense mosaic of highly predictable new sub-communities when living in a mound environment, even within a seafloor topography as modest as one meter. The most prominent distributional features may be summarized as follows: A) Free-living bryozoans (0-10 % of the bryozoans) exhibit a very clear mound-related distribution, with no specimens at all along the mound crest, and an increasing diversity and density into the intermound basin; encrusting bryozoans, on the other hand, are at their most abundant along the mound crest. B) Echinoderms (mostly irregular echinoids) show a distribution largely similar to the free-living bryozoans. C) Secondarily free-living, apedunculate brachiopods are restricted to the inter-mound basin.


Scott Lidgard and Steven Hageman
Department of Geology
Field Museum of Natural History
Roosevelt Rd. at Lake Shore Drive
Chicago, Illinois, 60605, USA

Different bryozoan characters, techniques, and species concepts provide valid but completely different answers to the same questions... What species does this specimen belong to? How many species occur in this place?; How are these five species related to one another phylogenetically? Is there a trend in species diversity with depth or latitude or geologic time? Here we survey many combinations of characters and techniques that are potentially useful in recognizing bryozoan species. In practice, species recognition usually precedes the adoption of a particular species concept, or the manner in which species are used in a particular study. Certain characters and techniques are better than others for answering particular questions, but none is best in all situations. Bryozoan taxonomy has disregarded many morphological and developmental characters of the bryozoan life cycle, biochemistry, and especially nucleotides. For the most part, bryozoan taxonomy has advanced little beyond the use of binary and multistate characters that are compared using keys and the experience of taxonomists to account for variation. The few studies that have utilized clustering or ordination techniques, or that have analyzed biochemical or molecular characters, indicate that bryozoan "species" can be discriminated to a much finer level, and that estimates of diversity based on traditional methods are conservatively low. From an evolutionary perspective, the lines of descent of a given gene or other character form diverse and numerous trees that are constrained within a given phylogenetic (species) tree. As bryozoan taxonomists, we may attempt to recognize species or reconstruct species trees by limited sampling of the distribution of populations and colonies and fragments and zooids and their constituent parts. Yet limited sampling, allopatric occurrences, errors in gene replication, gene duplication and extinction, hybridization, self-fertilization, asexual reproduction, polymorphism and developmental plasticity, or taphonomy can dramatically bias or even prevent species recognition. Our survey also indicates that concordance or covariance of characters, rather than the characters alone, may be more informative of species level taxonomy. We might do better to think of bryozoan "species" as a zone of resolution rather than a sharp boundary in a hierarchy from populations where reticulation and hybridization are common to discrete species taxa where these processes are uncommon. Since keys, ordination techniques, isozyme electrophoresis, and nucleotide fragments and sequence analysis permit increasingly greater exposition of this zone, the selection of characters and species recognition techniques should be explicit, and the limitations of these choices should be stated, when using bryozoan species.


Michael A. McCartney
Smithsonian Tropical Research Institute
Apartado 2072, Balboa, Republic of Panamá

Early treatments of sexual selection, including Darwin's, dismiss it as at best a weak force in sessile hermaphroditic organisms like bryozoans. To counter this conclusion, I will review the results of several field measurements of reproductive success, using the cheilostome Celleporella hyalina, that indicate strong potential for sexual selection. Male-male competition for fertilizations is fierce, and colonies investing more heavily in male gonad (male zooids) gain a considerable competitive advantage. Consequences of sexual selection are apparent, both in patterns of life history and of sex allocation. Onset of maturity and senescence occur earlier in male zooids than in female zooids, indicating sexual selection for earlier male zooid maturity and fecundity selection acting more strongly on female zooids to prolong their lifespan. Sex allocation is much more strongly male-biased than would be expected for a sessile organism with limited gamete dispersal, indicating that sexual selection favors increased allocation to male function. Gender differences in allocation and life-history strategy within colonies are a striking illustration of the uncoupled manner in which gender-specific natural and sexual selection can act in hermaphroditic individuals. Other reproductive traits of bryozoans, including the pronounced dimorphism and unisexuality of C. hyalina sexual zooids, may be molded by sexual selection


Frank K. McKinney
Department of Geology, Appalachian State University
Boone, North Carolina 28608, USA

Diverse Bryozoa encrust individual, 3-8 cm valves of several species of equivalved pelecypods that litter sand substrates 20-50 m deep in the northeastern Adriatic Sea. Cheilostome species with indeterminate, extensive sheet growth commonly occur on both outer convex (typically upper, exposed) and inner concave (typically lower, cryptic) surfaces of valves, although most favor convex surfaces to some degree and more commonly reach larger sizes and sexual maturity there. In contrast, species--both cheilostome and cyclostome--that produce small colonies and tend toward regularly circular outlines, more commonly occur on concave surfaces. Encrusting Ascidia, Porifera, and--in the shallower waters -Corallinacea are much more prolific on convex than on concave valve surfaces. It is hypothesized that larval settlement patterns are the immediate cause of the different patterns of distribution, although the patterns ultimately are related to probability of surviving overgrowth interactions. Larvae of small, slowly growing species with low potential for overgrowing competitors apparently show greater selectivity for cryptic surfaces. Larvae of larger, more rapidly growing species with higher potential for overgrowing competitors apparently show less selectivity about exposure of surfaces on which they settle. Such distinctly different settlement preferences suggest that they are the historical result of different probabilities of survival to reproduction in interactions with competitors of other taxa, including vigorously growing members of the taxa listed above.


Frank K. McKinney
Department of Geology, Appalachian State University
Boone, North Carolina 28608, USA

Interpretations of the phylogenetic origins of the Paleozoic fenestrate bryozoans can be organized into the four sets: 1) the phylloporinids are treated as a part of the paraphyletic order Trepostomida, from which the Cryptostomida (including the non-phylloporinid fenestrates) were derived; 2) the phylloporinids are considered to be the stem group of the Fenestrida, originating within the paraphyletic arthrostylids; 3) the phylloporinids are considered to be the stem group of the Fenestrida, originating within the paraphyletic bifoliate cryptostomes; and 4) the phyloporinids are considered to be a sister-group of the other Paleozoic fenestrates, both of which are more closely related to cheilostomes than to stenolaemates. Re-examination of the data on which the four types of interpretations were made suggests that the sister-group of the Paleozoic fenestrates is most likely one of the "cryptostomid" groups (arthrostylids or bifoliates)


Pierre Moissette
UFR des Sciences de la Terre, Université de Lyon I, 27 Bd du 11 novembre,
69622 Villeurbanne Cedex, France

Most paleoenvironmental reconstructions using bryozoans are based on ecological data -especially bathymetry- gathered on species living in present-day seas. Unfortunately, the habitat of many, especially rare, Recent bryozoan species is still often poorly known. However, some extant species are more abundant in fossil deposits or have a long fossil record offering a larger number of samples for study than in the Recent. In the corresponding fossil assemblages they are often associated with numerous other modern bryozoan species (and also other organisms) whose ecological requirements are fairly well documented. Using the information given by these more abundant species, a better knowledge of the ecology of rarer Recent species can thus be gained. This is particularly true for late Cenozoic (Neogene) marine sediments where about 20% (Miocene) to 80% (Pliocene) of the bryozoan species are extant. A number of fossil assemblages have been investigated in the upper Miocene and Pliocene of the Mediterranean where bryozoan faunas are now relatively well known. In each case a census of the extant species was first made, followed by a study using as principal criteria the presence/absence and abundance of the various species whose ecological distributions are relatively well known in the modern Mediterranean, combined with an analysis of the associated zoarial forms. From their fossil record, the depth ranges of some Recent species have thus been more precisely defined. This unusual application of the principle of uniformitarianism is a relatively safe procedure since there is no reason to believe that important changes have occurred in the ecology of species that lived only a few million years ago. Nevertheless, care should always be taken to ascertain that fossil and Recent specimens described under the same name are indeed conspecific.


Hugo I. Moyano G.
Departamento de Zoología, Universidad de Concepción,
Casilla 2407, Fax 56-41-240280, Concepción, CHILE

In recent (1996) collecting trips the German research vessel Polar Stern gathered an unusual bryozoan collection from the Magellanic continental slope in the Cape Horn area. Although this area has been extensively investigated by the Challenger, Romanche, Hamburger Magalhaensiche, and Discovery expeditions many taxa including families, genera and species remain to be discovered. This has been the case of two collecting sites at 430 m and 780 m depth in the southernmost tip of the Southamerican continental slope. There a bryozoan set of more than 40 species showing an antarctic facies was collected. One third of them are new to Chilean waters and not less than three species new to science. In terms of quantity it is dominated by flustrine zoaria such as: AustrofIustro australis, Chartella notialis, Flustrapora magellanica, Himantozoum obtosum, SecurifIustra bifoliata and Adelascopora cf. divaricata. Qualitatively it includes cellariids such as Cellaria clavata, C. tenuis, Cellaria sp.n, Paracellaria cellarioides, Melicerita blancoae and Cellarinella dubia and, rare forms such as Ichthyaria oculata, Platychelina planulata, Orthoporidroides erectus, Pseudidmonea fissurata and probably calwelliid and petralielliid species. These findings confirm the necessity of renewing efforts to explore and sample the austral Southamerican continental slope in search of bryozoan taxonomic and zoogeographical novelties linking the southeastern Pacific, the southwestern Atlantic and the Antarctic peninsula.


James H. Nebelsick
Institute for Geology and Paleontology
University of Tübingen
Sigwartstr. 10, D-72076 Tübingen, Germany

Rounded celleporid bryozoans are characteristic for a number of Tertiary limestones. They can dominate facies and are thus of importance for biogenic sedimentation as a whole in these environments. In this study, growth form morphologies of celleporid bryozoans from the Lower Miocene Zogelsdorf Formation are investigated using detailed descriptive and statistical techniques. They are compared with various rounded bryozoans growth forms from other localities. Rounded bryozoans from the Zogelsdorf Formation constructed by the genus Cellepora occur with sizes ranging from less than 1 cm to more than 10 cm. Very few other organisms are involved in the growth of these biogenic structures. The specimens range from flattened to mushroom shaped to spherical forms and often show an obvious growth direction. Larger objects often show a "parasitic growth" of smaller rounded bryozoans. True circumrotary growth is, in fact, rarely present in the Cellepora colonies. These show a distinct basal center of origin as well as growth lines which allow the direction of growth to be observed. The complex taphonomy of the specimens includes encrustation, bioerosion, fragmentation and diagenesis. The comparison of the studied bryozoans to other rounded bryozoans of differing taxonomic, geographical and stratigraphic position show both similarities and differences concerning growth forms, size and sphericity. Both endogenic biological as well as exogenic environmental factors are seen to be responsible for the circumrotary growth forms of the bryozoan macroids. These conclusions are supported not only by general environmental considerations, but also by the population structure and sphericity of the colonies. The process of self encrustation inherently solves the problem of limited surfaces availability, and can also alleviate additional problems such as space and foo~ompetition through other organisms. In this respect, these bryozoans are similar to other "macroid" forming organisms including coralline algae, serpulids and foraminifera.


Claus Nielsen
Zoologisk Museum, Universitetsparken 15,
DK-2100 Copenhagen, Denmark

There is still no agreement about the systematic positions of entoprocts and ectoprocts in the animal kingdom. Ectoprocts (bryozoans) are usually treated together with phoronids and brachiopods in the group Lophophorata (Tentaculata), whereas the entoprocts (kamptozoans) are assigned to various positions. However, morphological evidence firmly places entoprocts in the spiralian protostomes. The cleavage pattern is spiral in both Pedicellina and Barentsia, and the larvae are almost schematic trochophores in some of the loxosomatids. Prototroch and metatroch of compound cilia and an adoral zone of separate cilia has been described in practically all the larvae studied so far. Mesoderm is formed from the 4d-cell in Pedicellina. There is no trace of coeloms, and the excretory organs are accordingly protonephridia. This indicates that the entoprocts have a position close to but not within the coelomate protostomes (Teloblastica), i.e. sipunculans, molluscs and annelids, which similarly have spiral cleavage and trochophore larvae. Related groups with spiral cleavage but without typical trochophores are platyhelrninths and nemerteans. The position of the ectoprocts is more problematic. Cleavage pattern and larval type are open to interpretation; the cleavage of Bugula is apparently biradial, but has been interpreted as a modified spiral cleavage. The structure, ontogeny and function of the tentacle crown do not indicate homology with the lophophores of phoronids, brachiopods and pterobranchs. Coelom formation does not resemble that of deuterostomes and nephridia are not found. The larval apical organ and associated nerves and muscles indicate protostomian affinity, and the cell lineage of the corona cells could be interpreted as identical with that of the trochophoran prototroch. This indicates that the ectoprocts are protostomes, probably related to spiralians. Molecular data, i.e. sequencing of 18S rRNA, has been used extensively to elucidate the radiation of the animal phyla and lower groups, but so far only with bewildering results. Phoronids and brachiopods come out as a monophyletic unit in a number of analyses whereas they are "mixed" with molluscs and annelids in other analyses. Analyses which include both phylactolaemates and gymnolaemates (stenolaemates have apparently not been sequenced) place these two groups interspersed with molluscan classes/orders, various annelids, pogonophorans, sipunculans, etc. No analyses have indicated that the "lophophorates" are a monophyletic group. Entoprocts have only been included in analyses of restricted numbers of metazoan phyla.


Anna Occhipinti Ambrogi
Dip. Scienze dell'Ambiente e del Territorio - Università degli Studi di Milano,
Via Emanueli, 15 20126 Milano - Italy

The environmental stress on the Lagoon of Venice unique ecosystem is increasingly worrying scientists and administrators; this has promoted a wealth of studies on the ecological system of the Lagoon. The results show that the variation in the hydraulic regime of tidal currents is mainly responsible for the heaviest consequences of metabolism of nutrients and pollutants inside the Lagoon. As far as the consequences on the natural biota a lack of knowledge is apparent on the distribution of organisms and the documentation of long term trends in the last decade. This paper deals with the use of Bryozoan community as indicators of biodiversity threats in the Lagoon of Venice based on a data base extending from 1978 to 1997. The lagoon of Venice is far from homogenous in its physical characteristics, so it must be divided for analysis into the four main sectors that behave differently in temms of the response of biotic communities to stress. In the Northern sector, urbanization is less pronounced, a clear salinity gradient is evident and the communities respond more likely to the overall trend of water quality due to land based inputs of the agricultural land surroundings; in the historical urban centre of Venice the local conditions of pollution are overwhelming, in the area of the so-called petrol canal, connecting the Adriatic sea to the industrial harbour of Marghera, the hydraulic currents are the main limiting factor for the development of biological communities, whereas in the southern most sector, less active tidal currents in the meanders of a lesser town aggregate, enhance the possibility of water eutrophication. The Bryozoan community in the past years has proved a useful tool for describing different water characteristics, as one could easily associate the presence of species to conditions of low salinity, high organic content, water velocity or marine influx. A comparative analysis of the results of summer samplings in the years 1989, 1993, 1994, 1996, 1997 attempted to verify the stability of the conditions assessed during the previous years. In fact a major reduction of the overall abundance of Bryozoan is apparent in the last two years, questioning the possibility of establishing further assessments by the use of this group. This very reduction is undoubtedly a signal of severe changes in the environmental conditions of the Lagoon. Moreover in the same period we have assisted to a spectacular invasion by an exotic species Tricellaria inopinata, that reached the maximum expansion during 1989, in the last year this species has undergone the same declining trend of the rest of the Bryozoan fauna. Bugula has almost disappeared, whereas some very rare species such as Buskia and very locally Zoobotryon have gained relative importance over the years. Biotic interactions are in this way connected with the changing of ecological conditions, providing a clue for detecting early signs of unbalanced conditions through the study of biodiversity in a group such as brackish water Bryozoans.


Aaron O'Dea
School of Biological Sciences, University of Bristol
Woodlands Road, Bristol. UK. BS8 1 UG
Beth Okamura
School of Animal and Microbial Sciences, The University of Reading
Whiteknights, Reading RG6 6AJ

Zooid size in Recent cheilostome bryozoans has consistently demonstrated ecophenotypic plasticity in response to environmental temperature. While changes in zooid size within colonies can result from a variety of factors, intracolonial variation in zooid size should also be a function of variation in temperature experienced by the colony over time. Thus, relative seasonal changes in the climatic regime of an ancient sea may be inferred through trends in intracolonial zooid size variation in fossil cheilostomes, providing a number of requirements are observed in colony and zooid selection. Furthermore, the degree of seasonality may be more accurately inferred by investigating intracolonial zooid size variation and colony size in tandem. For comparative purposes morphometric data for colonies from Recent assemblages in varied climatic regimes are presented, and the technique for investigating palaeoseasonality described. The approach is then applied to a collection of encrusting bryozoans from the upper Pliocene Coralline Crag in Britain. The results reveal a seasonal climate less pronounced than that of the seas around the British Isles at present, a conclusion which is then discussed in context with current knowledge of Pliocene climate, geography and oceanography.


Beth Okamura
School of Animal and Microbial Sciences
The University of Reading Whiteknights
P.O. Box 228, Reading RG6 6AJ
United Kingdom

Freshwater bryozoans remain a poorly studied group despite their global distribution and often local abundance in benthic habitats of both lotic and lentic environments. Like most freshwater organisms they occur as subdivided populations in discrete habitats. Such a distribution suggests that populations may conform to a metapopulation structure. A variety of ecological and genetic evidence collectively indicates that local populations of Cristatella mucedo indeed compose a metapopulation which is characterized by highly clonal sub-populations in southern England. Evidence that other freshwater bryozoans similarly conform to a metapopulation structure is considered. It is argued that since high levels of clonality may particularly predispose freshwater bryozoans to population fluctuations, local extinction, and re-colonization events, metapopulation structure may be required to maintain life cycles which entail exceedingly high levels of asexuality. Factors that may contribute to local population fluctuations and extinctions (parasites, predators, environmental deterioration due to pollution, algal blooms, animal vectors) and to the conservation of such metapopulations are reviewed, and similarities and differences to populations of marine bIyozoans are discussed. Despite the relative dearth of studies, freshwater bryozoans provide opportune systems for investigating numerous issues of fundamental ecological and evolutionary significance.


Joanne S. Porter, John S. Ryland
School of Biological Sciences, University of Wales Swansea,
Singleton Park, Swansea, Wales SA2 8PP
Gary R. Carvalho
Applied Biology Department, Hull University,
Kingston-upon-Hull, England, HU6 7RX

The bryozoan Alcyonidium is a benthic, sessile, colonial invertebrate which encrusts various substrata in the marine environment. Owing to its gelatinous morphology and indeterminate growth, there are few useful phenotypic characters and one of the main criteria used to characterise species has been reproductive strategy. Alcyonidium gelatinosum reproduces sexually by brooded, lecithotrophic, coronate larvae which settle soon after release. The primary zooids form new colonies by budding, and first mature within a year. A. mytili reproduces sexually by broadcast eggs, which develop into planktotrophic cyphonautes larvae and may live for eight to ten weeks in the plankton before settling, metamorphosing and budding into adult colonies. The development of the Randomly Amplified Polymorphic DNA (RAPD) assay using the Polymerase Chain Reaction (PCR) has greatly facilitated studies of similar colonial animals because it requires very little material and it may easily reveal a number of genetic polymorphisms which can be used to characterise individuals, populations and species. During the present study, RAPD markers have been identified and used to investigate intraspecific variation and population genetic structure in the two species. A variety of analyses were used which all gave similar results, showing that A. gelatinosum populations are significantly genetically differentiated in contrast with populations of A. mytili which are genetically homogeneous. Other species from the genus were also characterised using the RAPD technique. A molecular phylogeny was constructed using both the RAPD data and data from sequencing of mitochondrial DNA. These results will be discussed in relation to geographic patterns, ecological differences and evolutionary significance.


Joanne S. Porter, Paul Bloor, Peter S. Cadman, Barbara L. Stokell & John S. Ryland
School of Biological Sciences, University of Wales Swansea,
Singleton Park, Swansea, Wales, SA2 8PP, UK.

Tentacle number has often been used as a taxonomic character in bryozoan species.identification, particularly in the genus Alcyonidium Lamouroux. Here we investigate variation in tentacle number within population, within species and between species. For the epiphytic species A. hirsutum (Fleming), results from following a transect through the Fucus serratus L. zone suggest that tentacle number decreases from the upper shore to the lower shore. This result was consistent at all three localities studied. Results also showed that competition was an important factor influencing tentacle number; colonies in contact with conspecifics had a lower tentacle number, whilst those touching colonies of a different species were found to have increased tentacle numbers. Tentacle number was also found to increase with the size of the colony. Another epiphytic species, A. gelatinosum (L.), was compared with A. hirsutum. Intraspecific variation in tentacle number was found to be significantly different between localities for both species, and differences between the species were highly significant at all three localities. These results were then compared with two species which encrust rocks and other hard substrata. A. mytili Dalyell, which encrusts Mytilus edulis L. valves at MLWS level has a modal tentacle number of 16 which is low compared with that of A. hirsutum (18-20) and A. gelatinosum (19-20). Studies on a sublittoral species of Alcyonidium (as yet unnamed) from the Fleet lagoon, range from 15- 18, with a mode of 18. We postulate that a possible explanation for the observed variation in tentacle number could be the relative position of colonies on the shore. If a colony is entirely sublittoral then it may require fewer tentacles in its lophophores to acquire as much food as another colony which is growing intertidally and has less submerged time during which feeding may take place.


Samantha de Putron, John S. Ryland and Joanne S. Porter
School of Biological Sciences,
University of Wales Swansea,
Swansea, SA2 8PP, Wales, UK

The tanker Sea Empress grounded at the entrance to Milford Haven on 15 Feb 1996 spilling 72000 t crude oil. An investigation was initiated into effects of the spillage on the ecology of Alcyonidium spp. which form communities on Fucus serratus. At Solva (control site outside Milford Haven with separate populations of A. gelatinosum and A. hirsutum), A. hirsutum had settled early in 1996 since all new colonies were large in Aug; the season was confirmed in 1997 as Feb-Mar. A. gelatinosum colonies were still small in Aug 1996; settlement in 1997 occurred May-Aug. At Dale, lightly oiled, where these two species, plus a third (unnamed) species occur in a mixed community, A. hirsutum colonies were also large in Aug 1996 but the pattern of events in A. gelatinosum was unclear owing, it transpired, to the admixture of a look-alike congener with a different breeding season; in 1997 A. hirsutum (and probably Alcyonidium sp.) settled in Feb and A. gelatinosum in May-Jun. Solva and Dale thus showed rather similar patterns with temporal separation of the two settlement events. At Angle, severely oiled, only A. gelatinosum occurs on F. serratus. There was no young settlement present in Aug 1996. New settlement started in Oct and continued at a low level throughout winter, ending in May; then heavy settlement took place Jul-Sep 1997. Evidently the oiling delayed but did not totally prevent the production of larvae in 1996 but a more normal, though extended and late, settlement occurred in 1997. Both the timing and temporal separation of A. hirsutum and A. gelatinosum settlement at Solva and Dale contrast with the Menai Straits, where the two spp. settle simultaneously in Sep-Dec; we also present some data on the reproductive season in the British Isles of the unnamed species.


June R. P. Ross
Department of Biology, Western Washington University
Bellingham, Washington 98225, USA
M. A. Hamedi
Department of Geology, Tarbiat Modarres University
P.O. Box 14155-4838, Tehran, Islamic Republic of Iran
A. J. Wright
School of Geosciences, University of Wollongong
Wollongong, NSW 2522, Australia

Bryozoans from the thin carbonate member of the Katkoyeh Formation, east-central Iran, comprise a distinct and diverse assembage of trepostomates and cryptostomates. They include the trepostomates, Eridotrypa, Hallopora, a mesotrypid, and an amplexoporid?, and two cryptostomates, a ptilodictyine and a rhabdomesine. Conodonts from this carbonate member indicate a Late Ordovician (Caradoc) age. The bryozoan assemblage has both cosmopolitan and endemic elements and is part of the warm water faunas fringing Gondwana.


John S. Ryland
School of Biological Sciences,
University of Wales Swansea, Swansea SA2 8PP, Wales, UK

It has often been suggested, quite firmly so by Borg (1926), that gonozooid placement in crisiids is highly consistent within the internode: but is that really so? A study was made of gonozooid placement and branching patterns in long-internode species of Crisia in the collections of the Natural History Museum, London; principally C. aculeata, C. denticulata, C. elongata, C. ramosa and some incorrectly or un-named Crisia spp. The results on gonozooid placement will be presented, together with some consideration of the implications for what (little!) we know about fertilization biology. The presence of a gonozooid was found to modify the pattern of subsequent branching, often greatly so with respect to both the number of branches and their position in the internode. The clear nature of the results suggests that, owing to inadequate quantitative analysis, the potential value of gonozooid placement and branching pattern to the notoriously difficult process of species discrimination in Crisia has not yet been properly appreciated.
Borg, F. 1926. Studies on Recent cyclostomatous Bryozoa. Zool. Bidrag. Uppsala, 10: 181-507.


William G. Sanderson
Countryside Council for Wales, Plas, Peurhos
Pfordd penrhos, Bangor, Gwynedd, LL57 2LQ, UK
John P. Thorpe
Department of Environrnental and Evolutionary Biology, The University of Liverpool
Port Erin Marine Laboratory, Port Erin, Isle of Man, IM9 6JA, UK

The structure and dimensions of the feeding apparatus exhibit a strong influence on the likely food, food capture and food particle handling techniques employed by Bryozoa. The Antarctic cheilostome bryozoan, Himantozoum antarcticum (Calvet)-was cultured in the British Isles whilst experimentation was conducted on its feeding behaviour. During this time observations were made on the lophophore and tentacular cilia using light microscope and scanning electron microscope techniques. On the basis of morphology, it can be suggested that lateral cilia and ciliary reversal (Strathmann 1982a, b) are unlikely to be involved in the majority of particle captures in H. antarcticum. Further inferences are made concerning the nature of the likely food ingested by H. antarcticum. It also appears that under certain conditions, the lophophore may be capable of exhibiting morphological plasticity. Comparisons are made between data for the lophophore of H. antarcticum and available information for other species. How these results may relate to comparative feeding activity is discussed.


Scott Santagata and Russell Zimmer
3616 Trousdale Prkwy Allan Hancock Fdtn Rm 235
University of Southern California
Los Angeles, CA, 90089-0371

Bryozoan coronate larvae possess a variety of surface cell types which fall into two categories: those which contribute to the formation of the ancestrulae upon metamorphosis and those cell types which compose the larval transitory structures These transitory cell types have been described as having sensory, glandular, or locomotory functions. The application of vital mitochondrial (fluorescent) stains has proven to be a powerful cytological mapper while also discerning the relative "activity" (mitochondrial density and degree of fluorescence) of each cell type prior to metamorphosis. The greatest levels of cellular activity exhibited within the ascophoran Watersipora arcuata was found in the coronal cells, ciliated ray cells, vibratile plume, balancers, the paired ciliated ridges that flank the superior glandular field and ciliated plaque (border cells), and intercoronal cells 1/1 and 1/2. Cells which show lesser activity are the cells of the neural plate, ciliated plaque, oral ciliated cells, and intercoronal cells 3/4 and 5/6. The superior and inferior glandular fields, supracoronal cells, and the presumptive adult tissues (blasternal, pallial epithelium, and infracoronal cells) exhibit very low levels of staining. The ascophoran Celleporaria brunnea and the anascan Bugula neritina display a similar pattern except for the intercoronal cells the activities of which may be species specific. These data further support the idea that the intercoronal cells, balancers, ciliated ray, border cells and the already well acknowledged vibratile plume play important sensory roles. The notion that presumptive adult tissues possess little to no role prior to metamorphosis is also consistent with these findings.


Priska Schäfer
Geological-Paleontological Institute, Kiel University
Olshausenstraße 40, D-24118 Kiel, Germany

Holocene bryozoan communities and biogenic carbonates on open shelf banks are investigated in the polar to subpolar and boreal North Atlantic. Bryozoan community dynamics and processes of skeletal carbonate production and sedimentation are, envisaged with respect to (paleo-) oceanography and climate and their influencing the glaciomarine and postglacial development of the environment. Areas of prolific biogenic growth of carbonate secreting bryozoans associated with mollusks, balanids, brachiopods, serpulids, azooxanthellate corals, siliceous sponges, and foraminifera are the polar front, shelf break fronts, internal waves and downwelling Taylor currents with high seasonal productivity and hence increased food supply. Here, a variety of benthic communities dominated by or associated with bryozoans create facies belts that are controlled by the amplitude of sealevel fluctuations over the past 12000 years and by the nutrition of benthic ecosystems in fertile waters. Modern bryozoan communities on the open shelves did not evolve prior to 2500 years b.p. Biogenic carbonates in polar to subpolar shelf settings are preserved as lag deposits consisting both of early infaunal and late epifaunal communities due to interference of the Holocene transgression and glacioeustatic compensation of the continental shelves. This is in contrast to the temperate regions (i.e. North Brittany), where the sealevel curve describes a constant drowning and colonization by benthic communities occurred in a single event.


Jill S. Schellenberger and June R. P. Ross
Department of Biology, Western Washington University
Bellingham, Washington 98225, USA

Organisms, both animals and plants, have various processes by which they protect themselves, including preventing predation and settlement of larvae and other fouling of their outer surfaces, as well as maintaining free space around them. Recently, interest has turned to those chemical activities used by organisms to protect themselves. In addition to particular structures, such as vibracula and avicularia, cheilostomate bryozoans are one group that utilizes specific chemical substances for self defense. Two marine cheilostomate species from western Washington use antibacterial substances as part of their defense system. To test for antibacterial activity, the filter paper disc method was used. Crude extracts made from the anascan cheilostomate Bugula pacifica inhibited the growth of two local marine bacteria, as well as Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. A crude extract made from the anascan cheilostomate Tricellaria occidentalis inhibited the growth of B. subtilis. SEM photomicrographs indicated that T. occidentalis had higher densities of surface bacteria than B. pacifica. This observation tends to coffoborate the relationship between antibacterial activity and surface fouling. The bryozoan secondary metabolites have an antifouling role, keeping epibionts away from the bryozoan surfaces. As an extension of this finding antibacterial substances in these bryozoans may control or restrict the microbial film growth on and around them and, consequently, this enables the bryozoans to keep free the space on the substrate adjacent to them.


Joachim Scholz
Department of Geology and Paleontology, University of Hamburg,
Bundesstrasse 55, D-20146
Hamburg, Germany, Tel 49 40 4123 5040, Fax: 49 40 4123 5007 e-mail

Microbiologists generally agree that only 1% of all procaryotic and eucaryotic microorganisms occurring in natural environments have been cultivated. For example, the kingdom fungi probably includes 1.5 million species of which only 69000 have been taxonomically described (Colwell, 1995). Moreover, studies on fungi of the marine environment and their ecophysiology are greatly hampered by several still unsolved problems:
a) the definition of what is a marine fungus;
b) to prove that the fungus is really active in the marine environment and not only there as a "transient";
c) their quantification
This is especially true for the occurrence of fungi on bryozoan surfaces. Bryozoans host a variety of epizoic microorganisms. Some bryozoans are regularly covered by a epizoic microbial mat partly consisting of mycelia. Fungal hyphae colonize or attack both soft parts (frontal membranes) and exoskeletal parts such as oral spines. In comparison to processes of competition or predation, the control of bryozoan occurrence by potentially pathogenic fungi and other microorganisms is not well studied. From New Zealand specimen of the anascan species Chaperiopsis cervicornis (Busk), the following species of fungi belonging to different genera of the Fungi imperfecti have been isolated with the diluting technique (Kochscher Plattenguss), and identified by means of cultivation: Gliocladium roseum (Bain), Phoma leveillei (Borema & Bollen), and Exophiala pisciphila (McGinnis & Ajello). E. pisciphila is known as highly zoopathogenic. The physiological kind of association of the other two species with the living bryozoan "sediment" is not yet known. Evidently, fungal mycelia epizoic on C. cervicornis spines delay overgrowth by other bryozoan species which compete for space.
Colwell, R.R., Clayton, R.A., Ortiz-Conde, B.A., Jacobs, D. & Russek-Cohen (199S): The Microbial Species Concept and Biodiversity. -In: Allsopp, D., Colwell, R.R. & D.L. Hawksworth (eds.): Microbial Diversity and Ecosystem Function: 3-16 (Wallingford, Oxon).
Sterflinger, K. & Scholz, J. (1997): Fungal infection and bryozoan morphology. -Courier Forschungsinst. Senckenberg (in press) (Frankfurt Am.).


J. Scholz & G. Hillmer
Department of Geology and Paleontology, University of Hamburg,
Bundessttrasse 55, D-20146
Hamburg, Germany, Tel. - 49 40 4123 5040~ Fax 49 40 4123 5001

Laminated crusts composed of bryozoan sheets are frequently found. There is some evidence that this peculiar structure is stimulated by confrontational processes with benthic micro organisms (microbial mats). Self-overgrowth is a regular bryozoan defense mechanism against mat overgrowth (Scholz & Krumbein, 1996). In most cases, the mats do not lithify ("potential stromatolites") and induce a considerable carbonate production by bryozoans. Sponge mats, cyanobacteria, diatoms, and pathogenic fungi have similar effects. If the epizoic mats agglutinate sediment, processes can also be recognized in the fossil record (Lee et al., in press). If the overgrowth interactions between bryozoans and (epizoic) microbial mats show a reversible pattern, cyclic competitive intergrowth can result in the formation of high-frequency bryo(zoan) stromatolites. This type has been described from Recent aphotic zones (submarine caves and upper bathyal) from the Philippines and the Gulf of Aqaba, and from shallow marine habitats of New Zealand region (Scholz, 1996). The potential for the evolution of bryostromatolites, and the radiation of Upper Cretaceous bryozoans in general (see Voigt 1979) may have been enhanced by the radiation of slime-producing benthic diatoms in the mid-Cretaceous (see Riding 1994). Aside from high-frequency structures, low-frequency bryostromatolites are formed by postmortal and microbially induced lithification inside bryozoan zooecial cavities. Seasonal fluctuations of environmental parameters control a phase displacement of bryozoan and microbial mat/stromatoid growth. One of these undulating factors is salinity. While bryozoan crusts (and serpulids) grow at euhaline conditions, the microbiata - for example the coccoid cyanobacterium Pleurocapsa - precipitate carbonate during yearly periodes of hypersalinity and low sealevel stands. Lithification is supported by sediment-trapping fungal mats The interplay can result in the construction of meter-wide reef structures such as present in the Coorong lagoon and Lake Clifton (Southern Australia) (see Sprigg & Bone 1993; Scholz 1996). It is assumed that several modern stromatolites are in fact bryostromatolites.
Lee, D. E., Scholz, J. & D., P. Gordon (in press). Paleoecology of a Late Eocene mobile rockground biota from north Otago, New Zealand. - Palaios.
Riding, R. 1994. Stromatolite survival and change: The significance of Shark Bay and Lee Stocking Island subtidal columns. - In: Krumbein, W. E., Patepson, D. M. & L-J. Stal (eds.): Biostabilization of Sediments: 183-202. Oldenburg (Universität Oldenburg, BIS). 526 pp.
Scholz, J. 1996. Eine Feldthcorie der Bryozoen, Mikrobenmatten und Sedimentoberflächen. Habilitation thesis, Faculty of Geosciences, University of Hamburg. 366 pp.
Scholz, J, & Krumbein, W. E. 1996. Microbial mats and biofilms associated with bryozoans. In Gordon, D. P., Smith, A. M, & Grant-Mackie, J. A. (eds.). Bryozoans in space and time. 293-298, National Institute of Water & Atmospheric Research. Wellington.
Sprigg, M. & Bone, Y. 1993. Bryozoa in Coorong-type lagoons, Southem Australia. Transactions of the Royal Society of S. Aust. 117(2): 97-95.
Voigt, E. 1979. Vorkommen, Geschichte und Stand der Bryozoen des Kreidesystems in Deutschland und benachbarten Gebieten. In: Aspekte der Kreide Europas. IUGS Series A/6: 171-210.


Nils Spjeldnaes
Department of Geology, University of Oslo
P.O. Box 1047, Blindem, N-0316
Oslo, Norway

Two cases of cryptic bryozoan environments are reported from the littoral of Gambia, West Africa. The first is connected to "reefs" consisting of highly porous iron-cemented sands, and boulders of the same rock in littoral sands, which may be rich in heavy minerals. The underside of the boulders and big stones contain a fauna consisting of bryozoans, molluscs and tubiferous worms. They are not -as ordinary cryptic faunas- living in open cavities, but are sitting directly in contact with the sand. They obtain nutrients and oxygen through the pore-water, which has a rather strong, tide-driven circulation, which has been investigated. All the forms met with are know to tolerate at least intermittent low oxygen levels, and are known also from more ordinary cryptic environments. Local "extinctions" due to lack of oxygen is common, and repeated overgrowth on dead, often ironstained, colonies are common. Two different types are common. One (or more) species of cribilinid bryozoans settle on the central parts of the boulders, indicating that the larvae migrated through the sand, as meiofauna. They form small colonies, which are soon overgrown with larger, rapidly growing form, with larvae settling at the water- sediment interfase. Repeated "cycles" of such "pioneer" and "climax" associations are found on most boulders. A similar, but not identical fauna is found in the open, waterfilled cavities in the "reef' itself . The cavities have a complex topography, and even if the same species of bryozoans as under the boulders are found, the association and quantitative distribution is different. Among the forms only observed in the "reef' cavities, is the phosphatic brachiopod Discina, the only living representative of this group, which flourished in the early Paleozoic. Some of the movable, upper valves of this brachiopod are overgrown with specimens of the bryozoan genus Hippoporidra, which is normally know as a symbiont growing on gastropod shells inhabited by hermit crabs. These bryozoans seems to prefer a movable substrate, but it is surprising to find them in a cryptic environment, as it is one of the few bryozoans which normally live under well lighted conditions, together with the pagurids. The other cryptic environment, is on the inside of dead specimens of Pinna. The scenario seems to be that a meadow of dead specimens, still sitting in their normal life-position, just under normal wave-base offered substrate to cryptic species. Later the shells were uprooted by heavy stones, and washed up on the beach. The fauna contains some species (of bryozoans, and worms) which are known from other cryptic environments, but in addition there are also many others, both bryozoans, oysters and foraminifers which normally occur in open environments. An undescribed membraniporid showed an unusual contact relationship, as it did not overgrow conspecific colonies, but regularly fused into larger "mega-colonies". Other encrusting species had more variable contact relationships, with overgrowth, even of conspecifics, or formation of vertical walls at the contact.


Paul D. Taylor
Department of Palaeontology
The Natural History Museum
London SW7 5BD, UK

Characters form the basis of all systematics: they are necessary to distinguish between taxa, and are essential in the construction of phylogenies from which classifications that reflect genealogy can be derived. Phylogenies only become reliable and classifications robust when a large number of non-conflicting characters are available. The key problem in cyclostome systematics is finding a sufficient number of useful characters. Sequence data have yet to become available, and soft part morphology is poorly documented in modern cyclostomes and totally lacking in fossils. For the bulk of cyclostomes, only skeletal characters are currently known, and even these are inadequately described and frequently plastic (e.g. colony-form) and/or not always developed (e.g. gonozooids). To obtain a fully resolved phylogeny of the 350 cyclostome genera described requires a minimum of 351 characters, a figure far in excess of the number of characters currently documented. The only pragmatic approach is to recognize a priori putatively monophyletic subdivisions, such as suborders, based on existing classifications, and then to analyze these individually before combining the results. However, new research on skeletal macrostructure and ultrastructure using SEM is beginning to find major problems even with the suborders of cyclostomes. The one extinct (Paleotubuliporina) and five extant (Tubuliporina, Articulata, Cerioporina, Rectangulata, Cancellata) suborders are fundamentally morphological grades, distinguished principally by the skeletal organization (free- or fixed-walled) of the autozooids and gonozooids. Paleotubuliporina lack gonozooids and have fixed-walled autozooids; Tubuliporina and Articulata have fixed-walled autozooids and gonozooids, the latter suborder being distinguished by its articulated colonies; Cerioporina have fixed-walled autozooids but free-walled gonozooids; and Rectangulata and Cancellata have free-walled autozooids and gonozooids but differ markedly in colony-form. The extinct Paleotubuliporina are a paraphyletic grouping of fixed-walled Paleozoic stenolaemates best regarded as stem-group stenolaemates. The remaining suborders together probably constitute a monophyletic cyclostome crown-group but their individual status and inter-relationships are very uncertain. For example, the Tubuliporina appear to lack a defining advanced character (apomorphy) and are likely paraphyletic, and evidence from skeletal ultrastructures suggests that the Articulata are diphyletic. Increasingly more cyclostomes are being discovered with mixed skeletal organizations which cut across the traditional subordinal classification. These include the extinct Eleidae (melicerititids), a clearly monophyletic group distinguished by their unusual operculate zooids but containing some tubuliporine- and some cerioporine-grade species, and several perplexing modern species from New Zealand exhibiting mixtures of fixed- and free-walled autozooids in the same colony. Progress towards the completion of a satisfactory cyclostome classification for the Treatise revision will be slow until these problems have been resolved and while there are so few taxonomists working on the group.


Jonathan A. Todd
Department of Palaeontology,
The Natural History Museum,
London SW7 SBD, UK.

Major methodological advances, particularly in morphological and molecular phylogenetics, have revolutionized the systematics of many major groups of organisms over the past twenty-five years. Unfortunately, they have yet to make much impact on higher-level bryozoan systematics. Here I will present a preliminary computer-based (PAUP) phylogenetic re-assessment of the higher level relationships of non-phylactolaemate bryozoans by focusing on the detailed relationships of the skeletized clades - Stenolaemata and (Eu-)Cheilostomata - to the nonmineralized, structurally more simple, ctenostomes. It seems increasingly likely that cheilostomes were derived from an arachnidiid-like runner ctenostome in the Jurassic. The "most primitive" stenolaemates are widely considered to be corynotrypid 'cyclostomes'. These are amongst the earliest known bryozoans (Early Ordovician) and are again widely believed to have had a ctenostome-grade ancestry. Ctenostomes themselves date back to the Early Ordovician and have a rapidly enlarging fossil record consisting of borings and bioimmurations. Each of these styles is shown to preserve enough systematic information for the placement of fossil taxa in a Recent system. Two groups of PAUP analyses were undertaken; 1) Recent ctenostome superfamilies, 2) ctenostomes, basal cheilostomes and basal stenolaemates at the generic level. The first analysis showed stoloniferans to be highly derived. When the resultant consensus cladogram is calibrated using the fossil record it reveals that almost all ctenostome superfamilies had evolved by the earliest Ordovician. The most basal ('primitive") stenolaemates and cheilostomes have a runner morphology. Consequently this allows us to assess the interrelationships of stenolaemates, cheilostomes and ctenostomes solely by analyzing runner taxa. In the second group of analyses I do this by coding and analyzing together, at the generic level, a range of better-known Recent and fossil ctenostomes together with basal representatives of the two skeletized clades. Results strongly suggest that the ctenostomes represent a paraphyletic grouping in which both the Stenolaemata and (Eu)Cheilostomata are nested. A major revision of higher level bryozoan systematics is therefore necessitated. To conclude it is demonstrated that the lack of a suitable phylogenetic framework has hidden our view of the broadest patterns of phylogeny, changes in palaeoecology and comparative taxic diversity through the Phanerozoic.


Norbert Vávra
Institute of Paleontology, University Vienna
Geozentrum, AlthanstraBe 14, A-1090 Vienna, Austria

Bryozoan localities from the Austrian Neogene belong to different regional stages (Eggenburgian, Badenian and Sarmatian), within the development of the Central Paratethys. On the basis of detailed biostratigraphic correlations and a thorough documentation of sediment distribution for the Paratethys in general (e.g.: Rögl & Steininger, 1983; Steininger, Senes, Kleeman & Rögl, 1985) the development of bryozoan faunas for the central Paratethys has been studied in coonnection with biogeographical aspects and the configuration of seaways at different stages of the geographical development of this area. Transgression and regression cycles as well as major turnovers and special steps of development in the marine biosphere can thus be documented by bryozoan faunas too. A few most convincing examples of this kind are discussed in detail: the migration of bryozoan faunal elements during the -Late Eggenburgian from the Western Mediterranean resp. the Rhone Valley via Switzerland and Bavaria into the Austrian Molasse Zone being one example. This seaway brought faunal elements (e.g. Steginoporella rhodanica, Onychocella demarcqi and others) from the Rhone valley to the area of Eggenburg. The Langhian marine faunal peak can also be shown to be valid for the development of bryozoan faunas - the "Upper Lagenid Zone" yielding the highest diversity of bryozoa in the Central Paratethys. The reestablishing of the Indo-Pacific connection at 16.8 ma can also be proved by special faunal elements like species of the family Hiantoporidae (Tremogasterina areolata, Tremopora radicifera) and others. Different bryozoan faunas of the Badenian stage being attributed to zones of different age having been carefully compared show detailed trends of faunal development. The disconnection of the Paratethys basins has triggered an endemic faunal evolution and has also had a severe influence on bryozoan faunas: a sharp decrease of diversity, and a sometimes remarkable biomass being produced by a few genera only (e.g. Schizoporella, Cryptosula) are outstanding features for the few bryozoan localities of Sarmatian age. On the basis of material and literature data available for bryozoan faunas of the Neogene of the Mediterranean detailed comparisons conceming the faunal development are possible. Such studies being at the present time still in a somewhat preliminary stage, are to be continued in near future however.

(Bryozoan studies supported by the "Fonds zur Förderung der wissenschaftlichen Forschung, project P09561-GEO)


Kerstin Wasson
Department of Biology, University of California
Santa Cruz, CA 95064, USA

Sex allocation theory (SAT) has been shown to be an extraordinarily powerful tool for predicting and understanding patterns of sexual reproduction in natural systems. SAT is one of the rare instances of evolutionary theory in which predictions are broadly applicable across disparate phylogenetic and functional systems. However, the predictions of SAT remain largely untested for one major group of aquatic organisms, colonial animals. In many regards, colonial animals resemble plants: they are mostly sessile, and must respond to environment variation by plasticity in growth and sexual strategies, rather than by mobility. Monoecious plants--those with both male and female flowers on the same plant--have been shown to respond to environmental variation by altering the proportion of male to female flowers. Colonial animals, too, may be monoecious--they may have separate male and female zooids within the same colony. However, few analogues to the botanical experiments have been carried out with colonial animals to test whether they too have plastic sexual strategies or to examine the directionality of that plasticity. I have begun to examine the plasticity of sexual strategies in two monoecious colonial animals, the bryozoan Hippodiplosia insculpta, and the kamptozoan Barentsia discrete. I am developing and testing theoretical predictions based on the major premise of SAT: that organisms should adjust their allocation to male vs. female function in such a way as to maximize fitness under differing environmental conditions. By manipulating environmental factors, I am examining plasticity of intracolonial sex ratio, timing of male vs. female maturity within colonies, and location of male vs. female zooids within colonies. For instance, I predict that under food limitation, male reproductive output suffers much less than female reproductive output, so that starved monoecious colonies should invest more heavily in male zooids than do well-fed colonies. Another prediction is that colonies should respond to the sex ratio of neighboring colonies by overproducing the rarer sex; a colony surrounded by colonies with sex ratio biased towards male zooids should respond by making relatively more female zooids. I also predict, based on local mate competition theory, that the intracolonial sex ratio of colonies at very low density will be more heavily biased towards female zooids than those at high density. I will discuss my preliminary results testing these hypotheses, and will consider the extent to which variation in sex ratio should be understood as an adaptive strategy, and the extent to which it is shaped by developmental and phylogenetic constraints.


Michael J. Weedon
Paul D. Taylor
Department of Palaeontology, The Natural History Museum,
London SW7 5BD, U.K.

Biomineralized skeletons of calcium carbonate are present in all cheilostome bryozoans but their mineralogy and ultrastructure vary between species. In order to infer the primitive condition of the cheilostome skeleton, we have studied the skeletal ultrastructures of species belonging to the primitive suborders Inovicellina (Aeteidae), Scrupariina (Scrupariidae, Eucrateidae) and Malacostegina (Membraniporidae, Wawaliidae, Electridae). Skeletons of these anascans may be calcitic or aragonite, and exhibit a wide array of ultrastructural fabrics. The following ultrastructures are recognized: planar spherulitic, wall perpendicular prismatic, wedge-shaped granular, acicular/rod-like, fibrous platey, and rhombic semi-nacre. Individual walls usually contain combinations of two or more of these fabrics. Most common amongst the ultrastructural types is wall-perpendicular prismatic fabric, which may be either calcitic or less often aragonitic. This fabric is present not only in primitive Recent species but also in the oldest fossil (Wawalia from the Lower Cretaceous) with walls sufficiently well-preserved for study. It seems likely that wall-perpendicular prismatic calcite represents a basic, primitive fabric in cheilostomes. Interestingly, while the other fabrics have parallels among stenolaemate bryozoans which evolved biomineralized skeletons independently, wall-perpendicular prismatic fabric seems to be unique to cheilostomes among bryozoans.


Judith E. Winston
Virginia Museum of Natural History, 1001 Douglas Avenue
Martinsville, Virginia 24112, USA
Peter J. Hayward
School of Biological Sciences, University of Wales
Singleton Park, Swansea, Wales SA2 8PP, UK

The purpose of this six year project was to carry out a distributional survey and species inventory of the little known bryozoan fauna of the northeast coast of the United States (Maine to Virginia). Collections were made at more than 100 previously unstudied localities. Most sampling was done intertidally, but a number of subtidal sites in the Gulf of Maine were also surveyed. Additional information and collections were obtained from ecologists working on benthic surveys or other projects in the study area and by exarnining museum specimens of bryozoans from the Gray Museum at the Marine Biological Laboratory, the Virginia Institute of Marine Science, and the National Museum of Natural History. A preliminary species list includes 141 species: 13 species of cyclostomes, 25 species of ctenostomes, and 103 species of cheilostomes. Twenty species (14% of the fauna) needed to be named. Ten of these were species which had been misidentified in the past; species which had been called by the names of British or European species by previous workers, but which on further examination proved to be distinct western Atlantic species. Another 10 species were completely unknown previously. The significance of this finding lies in the fact that most of the twenty are common inshore and intertidal species which have been studied by ecologists and collected by students in invertebrate biology classes for years. The most unique areas in terms of bryozoan fauna were the spatially isolated "lobster holes" in 60-120" depths in the Boothbay-Damariscotta, Maine region. In the Gulf of Maine rocky intertidal and subtidal areas attracted the richest bryozoan communities (both in numbers of species and abundance). About 40% of cheilostome species, 36% of ctenostome species, and 69% of cyclostome species ranged from Maine to Woods Hole. Only 15 (<11 % ) of bryozoan species (some of them offshore species) occurred along the whole northeast coast from Maine to Virginia. Although about 80% of our new collections were from Cape Cod south, they only confirmed the conclusions made by workers on other groups, that the Virginian Province of the American Temperate Region was lower in species than other temperate regions. However, in this region, the sounds behind barrier islands, with their associated oyster bars, were the source of richer, more diverse bryozoan communities than occurred on the open coast and shelf. Alcyonidium verrilli, found in subtidal channels in the lower Chesapeake Bay, probably has the greatest biomass of any species in the study area; its colonies wash up on the beaches literally by the ton, and the organisms inhabiting them (e.g., small amphipods and polychaetes) provide food for fish and shorebirds. The final report on this work will be published as an illustrated manual in the National Marine Fisheries Service series, Marine Flora and Fauna of the Eastern United States.


Timothy S. Wood
Department of Biological Sciences, Wright State University,
Dayton, Ohio 45435, USA
Lisa J. Wood
Department of Zoology, Michigan State University,
East Lansing, Michigan, 48824, USA

The taxonomy of phylactolaemate bryozoans places increasing emphasis on the surface microstructure of statoblasts. However, such detailed statoblast information is absent from species descriptions prior to 1980. The aim of this study was to locate as many type specimens as possible, to determine their condition and, if sufficient material exists, to examine statoblasts using both light and electron microscopy. We then combined this new information with traditional species descriptors to propose new systematic structures for phylactolaemate bryozoans. We surveyed the entire collection of phylactolaemate bryozoans. We surveyed the entire collection of phylactolaemate bryozoans at seven major museums in the United States and Europe: British Museum (Natural History) in London, Humboldt University Museum of Berlin, Natural History Museum of Amsterdam, Natural History Museum of Leiden, Natural History Museum of Sidney, U.S. National Museum (Smithsonian) in Washington, and the Zoological Museum of Hamburg. Additional material from Japan was loaned from the private collection of H. Mukai. In many cases type (or paratype) specimens were clearly marked; in other instances they were mislabeled, misidentified of simply not recognized. In general, there was much more material available than we had previously suspected. Statoblast type, form, and microstructure suggest many more species than those traditionally listed. They also suggest new taxonomic levels within the Phylactolaemata, especially in the large family Plumatellidae. More importantly, they illustrate the enormous voids in our knowledge of freshwater bryozoans that can be filled only by intensified field surveys and careful laboratory culture. With the rapid deterioration of the world's surface freshwater habitats such efforts warrant high priority.


Emmy R. Wöss
Department of Limnology, University of Vienna
AlthanstraBe 14, A-1090 Vienna, Austria

The Laxenburg pond has been a permanent site for Bryozoan studies over the last six years, as this eutrophic water body is characterized by high diversity of and intense settlement by seven different freshwater bryozoan species. From early May to early November 1992 120 artificial substrates (10 x 15 cm; three different materials) were exposed vertically 10 cm under the water surface on a raft to measure coverage of colonies weekly in the field. Bryozoan settlement began in late May on all of the substrates, with coverage up to 100 percent after several weeks. From early May 1995 750 artifical substrates (15 x 15 cm; plexiglass) on three rafts were installed in a vertical arrangement of panel-chains consisting of five panels per chain. The exposure depths were chosen to use the whole water column of the pond, which is maintained at a constant depth (ca. 2 m) from late April to early November by a shrice. In the course of this project, one panel-chain per raft was removed weekly to biweekly in 1995 and brought to the laboratory for detailed investigation of colony origin, size, overgrowth patterns etc. under a dissecting microscope. Intense settlement was again observed, with colony size decreasing from the upper towards the lower levels in all species. Freshwater bryozoans in general exhibit a great complexity in propagation due to the variety of floatile/sessile and short/long-living asexual resting stages. Plumatella casmiana, P. emarginata, P. fungosa and Hyalinella punctata - the four dominating species on the artificial substrates - represent different strategies in the mode of reproduction, dispersal and growth form as well as in their colonizing and competitive abilities.

Copyright © 1998, International Bryozoology Association
Edited by Phil Bock
Document modified 18th February 1998
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