<Emphasis Type="Italic">Tamanicella</Emphasis> gen. nov., a new genus of bryozoans forming the Late Miocene bioherms of Cape Panagia in the Taman Peninsula (Russia)

The bryozoans from the Late Miocene bioherms of Cape Panagia (Taman Peninsula) that have previously been attributed to Membranipora lapidosa (Pallas, 1801) are shown to belong to a new genus, Tamanicella gen. nov., which comprises two species: T. lapidosa (Pallas, 1801) and T. panagiensis sp. nov. T. lapidosa is represented by two life forms. One of them is characterized by bilaminate (more rarely unilaminate) sheetlike colonies with meandering lobes, and the other features erect branches. The lateral walls of each autozooecium in colonies of T. lapidosa have two multiporous septulae. T. panagiensis sp. nov. is characterized by massive multilaminate encrusting colonies and by the presence of three or four multiporous septulae in the lateral walls. The genus Tamanicella is placed in the family Membraniporidae. The diagnosis of this genus is provided and its two species are described.     

A new encrusting interstitial marine fauna from Brazil

Abstract. This paper reports the second occurrence of a sand‐grain encrusting interstitial epifauna dominated by bryozoans and polychaetes at a site thousands of kilometers from the first described occurrence of such a fauna 20 years ago. Such faunas seem to have gone almost unrecorded in the marine ecological literature, but they are potentially geographically widespread and ecologically significant, deserving recognition and further study by benthic ecologists. Although rooted‐erect and free‐living lunulitiform bryozoans can be abundant in soft‐bottom habitats, the presence of encrusting forms was, until recently, considered to be limited to patches of hard substrata. In 1985 and 1988, a new and seemingly unique habitat for encrusting bryozoans and other organisms on single grains of shell or sand was reported from the coastal waters of Florida, USA. Here we report a second discovery of an interstitial encrusting fauna from the continental shelf off the state of São Paulo, Brazil. In addition to the cupuladriid Discoporella umbellata, several species of bryozoans (9 cheilostomes, 3 ctenostomes, and 1 cyclostome) were found encrusting on or boring into sand grains from the 4 stations examined. Four species were found exclusively on sand to gravel size grains. The most abundant colonies, with ～1300–1500 colonies m^?2, belonged to a new species of Cleidochasma. New species of Trypostega and Reginella, each with up to 200–300 colonies m^?2, were also discovered. The grain‐encrusting bryozoans were characterized by their small size, and by the fact that sexual reproduction was initiated very early in colony growth; brood chambers (for the development of embryos into larvae) occurred in colonies having only a few zooids. Colonies of boring ctenostome and cheilostome bryozoans were even more abundant than those of grain encrusting forms, being present in almost every piece of shell (～5000–5500 colonies m^?2). The fauna also included representatives of other groups of encrusting organisms, especially tubeworms (11,000–13,000 tubes m^?2). Planned work on samples from additional stations on the São Paulo shelf will no doubt yield a larger number of species from various taxa and perhaps show some overlap in sand fauna species between the Brazilian and Floridian sites. In addition to the unique species of single grain encrusters, colonies of bryozoan species characteristic of larger subtidal hard substrata were also found on sand or gravel size grains, indicating that an interstitial refuge may be available to some epifaunal taxa and suggesting that this interstitial refuge, which remains almost completely unknown to benthic ecologists, may play a large role in determining distributions of those taxa.     

Structure of Adnate Colony Portions in Crisiidae (Bryozoa Cyclostomata)

The “rhizoidsrdquo; surrounding the base of the erect “colony” emanating from the ancestrula in the Crisiidae, especially the simple species Crisidia cornuta (L.), are a regular adnate system of autozooids. Each autozooid is composed of a proximal adnate part and a distal peristome (in some species kenozooids are possibly intercalated). The autozooid peristomes support erect branches identical in budding and structure with the branch emanating from the erect peristome of the ancestrula. Thus, the complete crisiid colony consists of an adnate system of ancestrula and autozooids, which form erect branches from their peristomes. The adnate zooid system is comparable in autozooid morphology and budding pattern with simple uniserial stomatoporids. The tentative hypothesis is proposed that the crisiid group has developed from primitive stomatoporids; the adnate zooid system of the stomatoporids apparently evolved peristomial budding to produce the erect colony branches characteristic of crisiids.     

Structural and taphonomic analysis of a columnar coralline algal build-up from SE Sicily

Unusual “coralligenous” build-ups were found at the infra–circalittoral boundary from SE Sicily. They are columnar, rising up perpendicularly from the bottom, and consist of an inter-growth of encrusting algae and invertebrates. A selected build-up and its longitudinal section, together with some thin sections of selected parts, were studied to detail the growth structures, composition and fabric of the trapped sediments. The coralline algae show a succession of “concentric”, “fruticulose” and “foliaceous” structures. The framework delineates cavities bounded by algal thalli, sometimes filled by sediments. The organisms constituting the framework were grouped into functional guilds (Fagerström, 1991): “primary frame builders” (mainly coralline algae); “secondary frame builders” (vermetids, serpulids and some bryozoans); “bafflers” (erect, flexible bryozoans, some sponges and soft algae); “binders” (encrusting bryozoans, some crustose coralline algae and serpulids); “destroyers” (a few endolithic algae, rare sponges and bivalves); “dwellers” (brachiopods, foraminifers, bivalves, small bryozoans and some motile organisms). The distribution pattern of taphonomic features (composition, grain size and distribution of sediments filling cavities; presence of cement and its location; mineralogical composition and crystal size), together with interactions between growth structures and functional guilds, allowed one to distinguish three taphofacies, each recording different environmental conditions. They have been tentatively related with cyclic sequences testifying to local hydrodynamic regimes, with subsequent slighter and stronger intensity phases, during the last 2200 years.     

Body wall morphology of Pentapora foliacea (Ellis and Solander) (Bryozoa,Cheilostomata)

The ascophoran Pentapora foliacea was studied from epoxy sections of skeletal and soft (hard-soft) tissues. The basal wall is double, indicating the colony grew as two independent layers, back to back. The structure of the vertical walls and interzooidal communication organs indicates that zooids were budded in the usual way as in most encrusting cheilostomes. Secondary layers of the frontal wall are of acicular aragonite. The ovicell develops as a flattened cuticular bladder in early ontogeny; the aragonitic layer of the frontal wall later engulfs it. A median vesicle, an evagination of the vestibular wall, is present but the eggs may be supplied with sufficient yolk to nurture the embryo. The overall ovicell structure is similar to that of hyperstomial ovicells in other cheilostomes.     

Operculate cyclostome bryozoans (Eleidae) from the Bohemian Cretaceous

Eleidae (‘melicerititids’) are unusual cyclostome bryozoans possessing operculate zooids and mandibulate polymorphs (‘eleozooids’) resembling the avicularia of cheilostome bryozoans. Here we describe 13 eleid species from the Cenomanian-Turonian of the Bohemian Cretaceous basin in the Czech Republic. Three species of Meliceritites are new: Meliceritites kankensis, M. stillativa and M. upohlavyensis. Reptoforicula gen. nov. is introduced for free-walled eleids with multilamellar encrusting colonies, containing the type species Reptoforicula zbyslavensis sp. nov. and R. vodrazkai sp. nov. Type specimens of three species erroneously assigned to Eleidae are refigured and their true affinities discussed. This study underscores the value of eleozooids in distinguishing between otherwise closely similar eleid species. The Bohemian late Cenomanian-early Turonian eleid fauna is dominated by encrusting species, a pattern that is typical of nearshore localities and contrasts with offshore chalks where erect, vincularian species are more numerous.     

Multizooidal Budding in Parasmittina trispinosa (Johnston) (Bryozoa,Cheilostomata)

Two principally different wall types occur in the bryozoan colony: Exterior walls delimiting the super-individual, the colony, against its surroundings and interior walls dividing the body cavity of the colony thus defined into units which develop into sub-individuals, the zooids. In the gymnolaemate bryozoans generally, whether uniserial or multiserial, the longitudinal zooid walls are exterior, the transverse (proximal and distal) zooid walls interior ones. The radiating zooid rows grow apically to form “tubes” each surrounded by exterior walls but subdivided by interior (transverse) walls. The stenolaemate bryozoans show a contrasting mode of growth in which the colony swells in the distal direction to form one confluent cavity surrounded by an exterior wall but internally subdivided into zooids by interior walls. In the otherwise typical gymnolaemate Parasmittina trispinosa the growing edge is composed of a series of “giant buds” each surrounded by exterior walls on its lateral, frontal, basal and distal sides and forming an undifferentiated chamber usually 2–3 times as broad and 3 or more times as long as the final zooid. Its lumen is subdivided by interior walls into zooids 2–3, occasionally 4, in breadth. This type of zooid formation is therefore similar to the “common bud” or, better-named, “multizooidal budding” characteristic of the stenoleamates but has certainly evolved independently as a special modification of the usual gymnolaemate budding.     

Larger foraminifera as a substratum for encrusting bryozoans (Late Oligocene,Tethyan Seaway,Iran)

Considering the diversity and abundance of larger foraminifera examined from a wide range of Late Oligocene to Early Miocene palaeoenvironments in the Tethyan Seaway, encrusting bryozoans make extremely little use of their tests as substratum. Significant encrustations by bryozoans were exclusively found on large (ø c. 6 cm), undulating tests of Lepidocyclina spp., on which, however, a remarkable 34 taxa of encrusting bryozoans were recorded. This shallow-water fauna of Chattian age was analyzed in respect of the bryozoan taxa present, colony growth type, and mode of budding, colony size, as well as onset of reproduction. Taxic and morphological similarities between the fossil assemblage and modern faunas encrusting mobile substrata indicate a long history of bryozoans as part of the interstitial habitat, while the tests of certain larger foraminifera may have played a significant role in the evolution of shallow-water bryozoans by providing substrata for encrusting species in otherwise unfavorable environments.     

Skeletal development in <Emphasis Type="Italic">Acropora palmata</Emphasis> (Lamarck 1816): a scanning electron microscope (SEM) comparison demonstrating similar mechanisms of skeletal extension in axial versus encrusting growth

Many Acropora palmata colonies consist of an encrusting basal portion and erect branches. Linear growth of the skeleton results in extension along the substrate (encrusting growth), lengthening of branches (axial growth) and thickening of branches and crust (radial growth). Scanning Electron Microscopy is used to compare the mechanisms of skeletal extension between encrusting growth and axial growth. In encrusting growth, the distal margin of the skeleton lacks corallites (which develop about 1 mm from the edge); in contrast, in axial growth, axial corallites along the branch tip form the distal portion of the skeleton. In both locations, the distal margin of the skeleton consists of a lattice-like structure composed of rods that extend from the body of the skeleton and bars that connect these rods. An actively extending skeleton is characterized by sharply pointed rods and partially developed bars. Distal growth of rods (and formation of bars) is effected by the formation of new sclerodermites. Each sclerodermite begins with the deposition of fusiform crystals (that range in length from 1 to 5 μm). These provide a surface for nucleation and growth of spherulitic tufts, clusters of short (<1 μm long) aragonite needles. The needles that are oriented perpendicular to the axis of the skeletal element (rod or bar), and perpendicular to the overlying calicoblastic epithelium, continue extension to appear on the surface of the skeleton as 10–15 μm wide bundles (of needle tips) called fasciculi. However, some crusts that abut competitors for space have a different morphology of skeletal elements (rods and bars). The distal edge of these crusts terminates in blunt coalescing rods, and bars that are fully formed. Absence of fusiform crystals, lack of sharply pointed rods and bars, and full development of sclerodermites characterize a skeletal region that has ceased, perhaps only temporarily, skeletal extension.     

Fire coral clones demonstrate phenotypic plasticity among reef habitats

Clonal populations are often characterized by reduced levels of genotypic diversity, which can translate into lower numbers of functional phenotypes, both of which impede adaptation. Study of partially clonal animals enables examination of the environmental settings under which clonal reproduction is favoured. Here, we gathered genotypic and phenotypic information from 3,651 georeferenced colonies of the fire coral Millepora platyphylla in five habitats with different hydrodynamic regimes in Moorea, French Polynesia. In the upper slope where waves break, most colonies grew as vertical sheets (“sheet tree”) making them more vulnerable to fragmentation. Nearly all fire corals in the other habitats are encrusting or massive. The M. platyphylla population is highly clonal (80% of the colonies are clones), while characterized by the highest genotype diversity ever documented for terrestrial or marine populations (1,064 genotypes). The proportion of clones varies greatly among habitats (≥58%–97%) and clones (328 clonal lineages) are distributed perpendicularly from the reef crest, perfectly aligned with wave energy. There are six clonal lineages with clones dispersed in at least two adjacent habitats that strongly demonstrate phenotypic plasticity. Eighty per cent of the colonies in these lineages are “sheet tree” on the upper slope, while 80%–100% are encrusting or massive on the mid slope and back reef. This is a unique example of phenotypic plasticity among reef‐building coral clones as corals typically have wave‐tolerant growth forms in high‐energy reef areas.     

Branching patterns, generating rules, and astogenetic trajectories in arborescent bryozoans

The terminal growth of bryozoans allows a reconstruction of their growth history and generating rules from the developed pattern. Three species of arborescent bryozoans share a bias in growth rate that favors reverser branches (those whose direction of growth is opposite that of their parent branch); this bias produces a common hummocky appearance to the top margin of the colony. Other differences in the growth rules, however, result in markedly different colony forms. For two species, the cue for splitting of branches seems to be the length of the branch; for the other, the cue seems to be the time since the last splitting. Simulations based on the distinction between reversing and nonreversing branches reproduce the hummocky pattern, but offer little insight into the underlying mechanism. Simulations based on occlusion, the line-of-sight blocking of the branches by each other, give similar patterns with fewer assumptions. These simulations also suggest that the pattern is due to a limited availability of nutrients to occluded growing tips, and that nutrients remain relatively localized within colonies. The actual determinants of colony form are likely to combine both nutrition and geometry.     

Hoeverella krauseae gen. et sp. nov., an unusual uniserial cheilostome bryozoan from the campanian of hannover

Hoeverellakrauseae gen. et sp. nov. is a peculiar runner-like anascan cheilostome bryozoan known from a single well-preserved specimen encrusting a belemnite guard. The colony comprises about 60 zooids, each of fusiform/pyriform shape and having a small “opesia” within which is situated an enigmatic ring structure. Several interpretations are possible for the ring structure: “regeneration”, closure plate, foreign organism inhabiting the zooecium, or socket of articulation for an erect branch or anAetea- like erect distal tube. Unusually for a runner-like bryozoan only one branch ramification occurs in the entire colony. The systematic position ofHoeverella is uncertain; however, it may be related to the electrid genusHerpetopora.     

Observations on Living Diastoporidae (Bryozoa Cyclostomata), with Special Regard to Polymorphism

The Diastoporidan colony consists of three zones: The marginal common bud, a narrow middle zone with erect peristomes and active polypides nourishing the whole colony, and a large central zone where the erect peristomes are detached, the secondary orifices thus formed are closed by terminal diaphragms, and the feeding polypides have degenerated. In many Diastoporidae the terminal closure is complete, but in several species the diaphragm is raised into a narrow, open tubule. In the latter type a dwarfed polypide with one tentacle only is regenerated: The autozooid is transformed into a heterozooid (“secondary nanozooid”), a unique phenomenon. Its function is unknown. The single tentacle of the “true nanozooids” of Diplosolen performs sweeping movements indicating a cleaning function. In two Plagioecia species “occasional nanozooids” were found, induced by disturbances of the colony growth. The function, if any, is unknown.     

Schischcatella (Fenestrata,Bryozoa) from the Devonian of the Rhenish Massif,Germany

Abstract: The Devonian fenestrate bryozoan, Schischcatella Waschurova, 1964 , possessed colonies in the form of low, erect bifoliate fronds that grew from an encrusting sheet‐like base with autozooecia arranged in biserial, bifurcating rows. This growth habit is unique in fenestrates, which normally had unilaminate arborescent colonies. Originally, Schischcatella was described from the Lower Devonian of Tajikistan. This article describes a new species, S. heinorum sp. nov., from the Middle Devonian of the Eifel (western Rhenish Massif, Germany) with additional material from the Lower Devonian of the Kellerwald (eastern Rhenish Massif, Germany). External and internal morphologies of this bryozoan have been studied using abundant material. The growth habit of Schischcatella suggests a completely different pattern of feeding currents than that in the normal fenestrate colony. The outflow of the filtered water occurred only on edges of colonies between rami. In the absence of chimneys (areas of vertical water expelling), such a functional morphology may have restricted extension of the colony in a distal direction. The evolution of Schischcatella is apparently an example of paedomorphosis, the genus evolved from an unknown semicosciniid species by the early ontogenetic interruption of colony development and further changes in the mode of growth.     

Geminivirus transmission and biological characterisation of Bemisia tabaci (Gennadius) biotypes from different geographic regions

Eighteen populations of Bemisia tabaci, collected from different geographic locations (North & Central America, the Caribbean, Africa, the Middle East, Asia and Europe), were studied to identify and compare biological and genetic characteristics that can be used to differentiate biotypes. The morphology of the fourth instar/pupal stage and compound eye structures of adults were investigated using scanning electron microscopy and found to be typical of the species among all biotypes and populations studied. Setae and spines of B. tabaci larval scales from the same colony were highly variable depending on the host plant species or leaf surface characteristics. The location and the morphology of caudal setae, characteristic of all B. tabaci studied to date, were present in all colonies. However, differences in adult body lengths and in the ability to induce phy to toxic disorders in certain plant species were found between biotypes or populations. The recently identified “B” biotype, characterised by a diagnostic esterase banding pattern and by its ability to induce phytotoxic responses in squash, honeysuckle and nightshade was readily distinguished from non-“B” biotype populations. None of the non-“B” biotypes studied, were found to induce phytotoxic responses. Nine populations examined showed typical “B” biotype characteristics, regardless of country of origin. All tested populations, determined as “B” or “B”-like biotypes successfully mated with other “B” biotype colonies from different geographic areas. Non-“B” biotype colonies did not interbreed with other biotypes. The B. tabaci populations were tested for their ability to transmit 15 whitefly-transmitted geminiviruses (WTGs) from different geographic areas with a wide range of symptom types. All WTGs were transmitted by the “B” biotype colonies and by most non-“B” biotype colonies, with the exception of three viruses found in ornamental plants which were non-transmissible by any colony. Some non-“B” biotypes would not transmit certain geminiviruses and some geminiviruses were more efficiently transmitted than were others.     

Diversity,structure and interactions of encrusting lithophyllic macrofaunal assemblages from Belgica Bank,East Greenland

Drop stones with lithophyllic macrofauna from Belgica Bank, Greenland Sea (79–81°N and 5–17°W) were collected during the Polarstern cruise in August 2000. The investigation focussed on species richness, diversity, abundance, and interactions of organisms colonizing rocks. On 101 stones collected by 10 dredges from nine sites, 113 taxa (58 genera, 38 families, 12 orders and 8 phyla) were recognized. Among the most abundant groups of organisms were foraminiferans, bryozoans and polychaetes, while the least abundant were anthozoans and ascidians. Abundance ranged from 1239 to 11,383 individuals m⁻² of rock surface area. Bryozoans were the most species-rich group, while anthozoans and ascidians were represented by the least number of species. Colonization occurred at various topographical levels and was classified into two categories. Stones were classified as primary space and were colonized by erect membranous, erect flexible, erect rigid, and flat encrusting organisms. The second level of colonization by epibionts occurred on erect forms of organisms (e.g. erect bryozoans) and was classified as a secondary space. Species composition and abundance between faunal assemblages of primary and secondary space differed greatly. Colonization occurred only on the top of stones and was considered a special adaptation to avoid burial by sedimentation and to enhance food supply. Only 3% of recruits were involved in any competitive interactions. Competition was considered to be of minor importance in structuring lithophyllic assemblages.     

Evolution of the colonial growth habit in the ordovician bryozoans of the class stenolaemata: Feeding adaptations (Leningrad Region,Russia)

Based on the study of the growth habits and the relief of the colony surface in bryozoans of the class Stenolaemata from the Lower (Latorp horizon) and Middle (Volchov and Kunda horizons) Ordovician of the Leningrad Region, these bryozoans are shown to develop from the simple, unilaminate colonies (B_I^β) to the massive colonies with a nodular surface and smooth columnar colonies (B_II^α), which subsequently evolved into the columnar-spiral (B_II^β) and more complex erect branching and fenestrate constructions (B_II^γ), and subsequently into the branching, articulate colonies (B_III^α). The apertures of autozooecia and the character of their arrangement on the colony surface changed correlatively from the circular (B_I^β) to polygonal and roundedpolygonal, randomly arranged apertures, and subsequently to the oval apertures (B_III^α) arranged in strictly regular longitudinal or longitudinal-diagonal rows or in a quincuncial pattern. Thus, the development of growth habits in the bryozoans under consideration has a progressive character. It is expressed in the progressive increase in the complexity of growth habits of colonies and in the more regular arrangement of apertures and other structures on the colony surface. The directionality of morphological changes in the growth habits of colonies of Ordovician bryozoans was apparently closely associated with the development of more complex environmental interactions of these bryozoans, especially with water currents supplying food particles. It is suggested that the high competitive ability of bryozoans of the class Stenolaemata at early stages of its development in the basin of Baltoscandia was apparently due to the better use of food resources.     

Bryozoaires des milieux récifaux miocèes du sillon sud-rifain au Maroc

Moissette, P. & Saint Martin, J_:P. 1995 11 30 Bryozoaires des milieux récifaux miocenes du sillon sud-rifain au Maroc. [Bryozoans from Miocene reef environments in the South-Rifian corridor of Morocco. In late Miocene coral reefs from the Fes area (Northern Morocco), bryozoans are the best-represented group. An inventory of the bryozoan fauna (59 species) was taken on two reefs with different organization and palaeogeographical situation in a late Miocene seaway between the Atlantic and the Mediterranean. A study of the bryozoans and their zoarial forms allows an improved reconstruction of reefal environments and available habitats. Membraniporiforrn (encrusting) colonies largely predominate, whereas celleporiforms (nodular colonies) are more rare. Rigid erect (vinculariiform, adeoniform, and reteporiform) and rigid articulated zoarial types (cellariiform and catenicelliform) are fairly well represented. At depths of about 10 m and on the reef front encrusting bryozoans were well developed in cryptic habitats on living coral substrates. Erect species lived in cavities provided by the coral framework, and plants offered flexible substrates for the attachment of epiphytal forms. □Bryozoa, coral reefs, Morocco, Messininn, pulueoecology. Dans les récifs coralliens du Miocène supérieur de la région de Fes (Maroc septentrional), les bryozoaires constituent, parrni les organismes conservés, le groupe le mieux représenté. Un recensement de la fame de bryozoaires (59 espèces) a été effectué dans deux récifs d'organisation et de situation paléogéographique différentes, dans un secteur de communication entre Atlantique et Méditerranée au MiocéFne supérieur. L'étude des bryozoaires et de leurs formes zoariales permet de proposer une meilleure reconstitution de I'environnement récifal et des habitats disponibles. Les colonies membraniporiformes (encrobtantes) predominent largement, alors que les cellepori-formes (colonies noduleuses) sont beaucoup plus rares. Les types zoariaux érigés rigides (vincula-riiforme, adéoniforme et rétéporiforme) et érigés articulés (cellariiforme et catenicelliforme) sont assez bien représentés. A des profondeurs denviron 10 m et dans la partie antérieure des constructions récifales, les bryozoaires encroûtants étaient bien développés dans des habitats cryptiques sur substrats coralliens vivants. Des formes dressées vivaient dans les cavités ménagées par le bâti corallien et des supports végétaux permettaient également la fixation de formes épiphytes. □Bryozouires, récifs coralliens, Muroc, Messinien, puléoécologie.     

Ecological Shifts in Mediterranean Coralligenous Assemblages Related to Gorgonian Forest Loss

Mediterranean gorgonian forests are threatened by several human activities and are affected by climatic anomalies that have led to mass mortality events in recent decades. The ecological role of these habitats and the possible consequence of their loss are poorly understood. Effects of gorgonians on the recruitment of epibenthic organisms were investigated by manipulating presence of gorgonians on experimental panels at 24 m depth, for Eunicella cavolinii, and at 40 m depth, for Paramuricea clavata, at two sites: Tavolara Island (Tyrrhenian Sea) and Portofino Promontory (Ligurian Sea). After 4 months, the most abundant taxa on the panels were encrusting green algae, erect red algae and crustose coralline algae at 24 m depth and encrusting brown algae and erect red algae at 40 m depth. Assemblages on the panels were significantly affected by the presence of the gorgonians, although effects varied across sites and between gorgonian species. Species diversity and evenness were lower on panels with gorgonian branches. Growth of erect algae and recruitment of serpulid polychaetes were also affected by the presence of the gorgonians, primarily at Tavolara. Crustose coralline algae and erect sponges were more abundant on E. cavolinii panels at 24 m depth, while encrusting bryozoans were more abundant on P. clavata panels at 40 m depth. Effects of gorgonians on recruited assemblages could be due to microscale modification of hydrodynamics and sediment deposition rate, or by a shading effect reducing light intensity. Gorgonians may also intercept settling propagules, compete for food with the filter-feeders and/or for space by producing allelochemicals. Presence of gorgonians mainly limits the growth of erect algae and enhances the abundance of encrusting algae and sessile invertebrates. Therefore, the gorgonian disappearances may cause a shift from assemblages characterised by crustose coralline algae to filamentous algae assemblages, decreasing complexity and resilience of coralligenous bioconstructions.     

Bryozoans and microbial communities of cool-temperate to subtropical latitudes—paleoecological implications

The environmental distribution of encrusting bryozoans settling on disarticulated and living bivalve shells has been recorded from five stations in Japan and New Zealand. Some insight into the observed distribution patterns emerges from information on the interaction of bryozoans with microbial mats. Advancing existing classifications, we have subdivided the encrusting bryozoan morphotypes into seven different growth types that largely reflect the biological potentials of bryozoans in competition for space on substrate surfaces. The frequency distribution of these types (s-/c-/m-/z-laminae, runners, spots, bryostromatolites) reveals the influence of microbial mats as a control factor of bryozoan substrate coverage. Microbial mats in turn are correlated with latitudinal gradients in Japan and New Zealand from cool-temperate to subtropical and tropical waters. Unlike erect bryozoans, laminar ones are probably underrated as facies fossils. Accordingly, laminar bryozoan growth types are reconsidered as a tool for paleoecological interpretation of marine hard substrate communities.