Bryozoan Colonies Research Articles

The Girvanella-like remains from Messinian marine deposits (Sardinia, Italy): Lagerstätten paradigm for microbial biota?

The lower Messinian marine sediments of the Capo San Marco Formation in the Sinis area (Sardinia, Italy) contain extensive carbonate buildups mainly made of microbialites. These microbialites exhibit general thrombolitic fabric and occur in meso-macroscopic scale as dominant cauliflower-like structures, digitations and encrusting rings. All the microbialites are here associated with serpulid tubes and bryozoan colonies. Examination of thin sections from microbialite samples reveal the presence of dense flexuous, not ramified and erect tubular micritic structures, with an external diameter ranging from 30 to 40 μm, all characters being very close to those of the Girvanella-type filaments. Although all microbialites show quite similar structural aspects, only two levels contain clearly visible networks of such filaments. The associated marine biota is diverse (cemented, borers, burrowers) related to the available biotopes (hard substrates, fine grained sediment, cavities…). The general scarcity of microbial remains in Messinian microbialites points out to the problem of taphonomic processes allowing a good preservation of microbial structures. The concept of Lagerstätten could well be extended to the preservation of microscopic organisms in the carbonate material. The discovery of Girvanella-like filaments demonstrates the implication of cyanobacterial organisms in the construction processes of the Messinian thrombolitic buildups. Furthermore, it is the first time that Girvanella-like microbialites are documented from Upper Miocene marine rocks.

Interpreting seawater temperature range using oxygen isotopes and zooid size variation in Pentapora foliacea (Bryozoa)

This is the first investigation of how two independent proxies for seawater temperature inference (zooid size variation and oxygen isotope ratios of skeletal carbonate) relate to the actual measured ranges of temperature experienced by cheilostome bryozoan colonies. Nine specimens of the bimineralic marine cheilostome bryozoan Pentapora foliacea (Ellis and Solander, 1786) were analysed, collected from ~18-m depth at two localities in Wales, UK—four from Skomer Island (51°42′510″N, 5°13′42.60″W) and five from Porth Ysgaden, Lleyn Peninsula (52°54′6.75″N, 4°38′47.34″W). The annual range of temperature implied by zooid size variability provides a good approximation of the actual range of temperature recorded by a datalogger. However, annual ranges of temperature reconstructed from skeletal oxygen isotope ratios were narrower, typically not showing the lowest temperatures experienced by the colonies. This can be explained by progressive thickening of zooid skeletal walls during the life of the colony that homogenises the temperature signal by time-averaging over the lifetime of the colonies. Our study provides evidence that a combined morphological isotope approach has great potential in the reconstruction of annual ranges in seawater temperatures from historical and fossil bryozoans, particularly for species that lack ontogenetic skeletal wall thickening and bimineralic skeletal composition. As cheilostome bryozoans have been common in benthic communities since the Late Cretaceous, they represent a valuable and underutilised resource for the interpretation of environmental regimes.

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 (BIβ) to the massive colonies with a nodular surface and smooth columnar colonies (BIIα), which subsequently evolved into the columnar-spiral (BIIβ) and more complex erect branching and fenestrate constructions (BIIγ), and subsequently into the branching, articulate colonies (BIIIα). The apertures of autozooecia and the character of their arrangement on the colony surface changed correlatively from the circular (BIβ) to polygonal and roundedpolygonal, randomly arranged apertures, and subsequently to the oval apertures (BIIIα) 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.

A parautochthonous shallow marine fauna from the Late Burdigalian (early Ottnangian) of Gurlarn (Lower Bavaria, SE Germany): Macrofaunal inventory and paleoecology

This paper describes and illustrates a diverse parautochthonous macrofauna from a single Upper Burdigalian (lower Ottnangian) horizon at Gurlarn in Lower Bavaria (SE Germany). In total, 80 different taxa are recorded in specific or open nomenclature; some 50 % of these taxa are bryozoans, followed by bivalves (16 taxa), cirripedes (7 taxa), echinoderms, corals (5 taxa each), brachiopods, fish (4 taxa each), serpulids, and gastropods (3 taxa each). The presence of additional organisms was documented by actualistic comparison based on indirect evidence such as drillholes, bite marks, and specialized growth forms of bryozoan colonies. Analysis of autand synecological indicators suggests that the fauna thrived in a near-shore shallow marine setting at a water depth of 5-20 m. Based on particular faunal elements and overall faunal composition we hypothesize that the environment is characterized by three distinct but interfingering habitats, i.e. (1) rocky slopes and boulders, (2) seagrass meadows, and (3) bryozoan meadows. Because similar, albeit less wellpreserved, faunas occur at several localities along the northern coast of the early Ottnangian Molasse Sea, the parautochthonous assemblage from Gurlarn provides an excellent example for the structure of these typical biota.

Flow-mediated feeding in the field: consequences for the performance and abundance of a sessile marine invertebrate

The ecology of sessile marine invertebrates that feed on waterborne particles is closely related to their surrounding fluid environment. However, few studies have quantified how water flow affects the feeding success of such organisms under field conditions and whether the results of shortterm feeding assays can predict longer-term patterns of growth and reproduction. I examined the influence of natural variation in current speed on the feeding success, colony growth rate and population abundance of an encrusting bryozoan Membranipora serrilamella using transplant experiments at nearshore reefs along the coast of Santa Barbara, California, USA. Feeding success was highest at intermediate ambient flow speeds (10 to 12 cm s–1) and lowest at low (0 to 5 cm s–1) and fast (> 20 cm s–1) speeds. Growth rates varied such that the greatest increases in bryozoan colony size occurred at reefs where average temperatures were the coolest and current speeds were intermediate. A test of the hypothesis that high feeding success translates into faster growth rates revealed that colonies with the highest predicted consumption grew the most. Further, spatial variation in M. serrilamella abundance mirrored that of colony growth, as percent cover of the bryozoan was highest at reefs where ambient current speeds were intermediate. These nonlinear functional relationships likely result from reductions in food delivery at low flows and deformation of feeding structures at high flows. The consequences of dynamic flow conditions for both short-term and integrated measures of performance suggest that flow-mediated food acquisition plays an important role in determining the distribution, abundance and morphology of encrusting bryozoans and other sessile, suspension-feeding invertebrates.

Unusual skeletal morphology and systematic description of a new Devonian cryptostome bryozoan from the Western Sahara

Palaeozoic bryozoan colonies display a large variety of skeletal elements. Various types of rod-like styles are mainly built by laminated and non-laminated (hyaline) skeleton. Typical styles consist of hyaline cores and surrounding laminated sheaths. They usually protrude on the colony surface as spines. In a new bryozoan genus from the Middle Devonian of the Western Sahara described here, styles do not protrude on the colony surface and are embedded within the laminated skeleton. They consist of fibrous material. This new type of styles, unknown from other bryozoans, is here called a “cryptostyle”. A special characteristic of these structures is their intensive reddish-brown colouration. This colouration is apparently caused by the presence of ferric iron between the individual fibres. The function of cryptostyles was apparently weight reduction and stabilising the skeleton. The general morphology of the new bryozoan, Cryptostyloecia hexapuncta gen. et n. sp., implies its systematic position within ptilodictyine cryptostomes, specifically the Family Ptilodictyidae Zittel, 1880.

Pliocene seasonality across the North Atlantic inferred from cheilostome bryozoans

Previous studies have shown an inverse correlation between zooid size in cheilostome bryozoans and ambient water temperature. This relationship underlies the MART technique which uses intracolonial variation in zooid size to predict mean annual range in temperature experienced by bryozoan colonies during their life. Here we apply the MART technique to study Early and Mid Pliocene bryozoans from Central America (Panama, Costa Rica), the USA (Florida, South Carolina, North Carolina, Virginia) and the UK (Suffolk) to reconstruct palaeoseasonality across a range of latitudes for the North Atlantic during the Pliocene Epoch. Compared to the present-day, our analyses suggest greater seasonality (ca 4.5 °C) in the southern Caribbean at the time of Cayo Agua Formation deposition (ca 4.25 Ma), in keeping with inferred upwelling prior to the closure of the isthmian barrier at 2.7 Ma. Bryozoans also indicate seasonal upwelling on the Gulf Coast of Florida in a similar manner to the present-day. Because upwelling can be highly localised and prone to spatial and temporal variation in the Gulf of Mexico today, it contributes little to a broad understanding of Pliocene North Atlantic waters. However, MART estimates for the coastal plain region indicate a general reduction in the annual range in temperature relative to the present, suggesting that the colder surface waters that today reach south to Cape Hatteras had less influence in Early to Mid Pliocene times. These results, along with evidence from other proxies, strongly support reduced seasonality and warmer conditions along the eastern seaboard of the USA in the Early to Mid Pliocene. Finally, the MART estimates amongst Coralline Crag localities provide evidence for an increased annual range in temperature in the southern North Sea than at present. Our study shows that bryozoan MART estimates provide a powerful, independent proxy for palaeoseasonality and is the first to demonstrate that the MART technique can be applied to infer palaeoclimates across a wide range of latitudes focusing on a variety of geological formations and geographical regions.

A Hirnantian (latest Ordovician) reefal bryozoan fauna from Anticosti Island, eastern Canada: taxonomy and chemostratigraphy

The Natiscotec outcrop on Anticosti Island, Canada (Ellis Bay Formation, Laframboise Member, Hirnantian, Late Ordovician), exposes a patch reef some 20–30 m in diameter, 2–3 m thick, with abundant rugose corals, as well as favositids and heliolitids. Reef capping and flanking sediments include typical Hirnantian brachiopods, such as Hirnantia , Hindella , and Eospirigerina . Within the reef peloidal microbialites encrusting bryozoan colonies are common. The bryozoan fauna includes three cystoporates, seven trepostomes, and three phylloporines. Two genera and two species are new: the cystoporate Natiscotecella tenuis n. gen. and n. sp. and the phylloporine Dilaminocladia natiscotecensis n. gen. and n. sp. Three more species are also new: the cystoporates Ceramopora clara n. sp. and Acanthoceramoporella spinigera n. sp. and the trepostome Revalotrypa honguedensis n. sp. Furthermore, we identify the three trepostomes Atactoporella aff. ortoni (Nicholson, 1874), Hallopora elegantula (Hall, 1852), and Monotrypella cf. aequalis Ulrich, 1882, and a phylloporine Parachasmatopora porkunensis Lavrentjeva, 1985. Four species are identified at generic level and in open nomenclature: the three trepostomes Lioclemella sp., Calloporella sp., and Trepostomata sp. and a phylloporine ? Ralfinella sp. The bryozoan fauna shows some affinities with the Late Ordovician fauna of Scandinavia. Stable carbon isotope investigations from brachiopod shells of the same outcrop yield values for δ13C of up to +6.7‰, which represent the highest values reported from the Anticosti succession so far. This indicates that the stratigraphic position of the outcrop is at or close to the peak of the globally recognized Hirnantian δ13C excursion.

The effects of infection by Tetracapsuloides bryosalmonae (Myxozoa) and temperature on Fredericella sultana (Bryozoa)

The myxozoan, Tetracapsuloides bryosalmonae, exploits freshwater bryozoans as definitive hosts, occurring as cryptic stages in bryozoan colonies during covert infections and as spore-forming sacs during overt infections. Spores released from sacs are infective to salmonid fish, causing the devastating Proliferative Kidney Disease (PKD). We undertook laboratory studies using mesocosm systems running at 10, 14 and 20 °C to determine how infection by T. bryosalmonae and water temperature influence fitness of one of its most important bryozoan hosts, Fredericella sultana, over a period of 4 weeks. The effects of infection were context-dependent and often undetectable. Covert infections appear to pose very low energetic costs. Thus, we found that growth of covertly infected F. sultana colonies was similar to that of uninfected colonies regardless of temperature, as was the propensity to produce dormant resting stages (statoblasts). Production of statoblasts, however, was associated with decreased growth. Overt infections imposed greater effects on correlates of host fitness by: (i) reducing growth rates at the two higher temperatures; (ii) increasing mortality rates at the highest temperature; (iii) inhibiting statoblast production. Our results indicate that parasitism should have a relatively small effect on host fitness in the field as the negative effects of infection were mainly expressed in environmentally extreme conditions (20 °C for 4 weeks). The generally low virulence of T. bryosalmonae is similar to that recently demonstrated for another myxozoan endoparasite of freshwater bryozoans. The unique opportunity for extensive vertical transmission in these colonial invertebrate hosts couples the reproductive interests of host and parasite and may well give rise to the low virulence that characterises these systems. Our study implies that climate change can be expected to exacerbate PKD outbreaks and increase the geographic range of PKD as a result of the combined responses of T. bryosalmonae and its bryozoan hosts to higher temperatures.

Space utilisation patterns of bryozoans on the Patagonian scallop <em>Psychrochlamys patagonica</em>

SUMMARY: We studied the bryozoan assemblage encrusting valves of the Patagonian scallop, Psychrochlamys patagonica, in 4 beds distributed along the continental shelf off Argentina to analyse (a) the distribution pattern of bryozoan colonies in different zones of the valves, (b) the influence of interspecific competition on assemblage composition, (c) whether encrusting species display different space utilisation strategies, and (d) whether bryozoan species richness and number of colonies vary in relation to host size. The assemblage was composed of 22 taxa and was dominated by Arachnopusia monoceros and Osthimosia eatonensis, which were at least one order of magnitude more abundant than any other species. Multivariate analyses based on coverage data of multiserial bryozoans separated the beds according to species richness rather than to geographic proximity and showed significant differences in assemblage structure between upper (left) and lower (right) valves and among beds. Competitive interactions occurred almost exclusively on lower valves, and more frequently in peripheral zones than in central zones of these valves. Correlations between valve area and number of bryozoan colonies, coverage and species richness were low but significant. Bryozoans were significantly more frequent, larger, and taxonomically diverse on lower valves than on upper valves. The uniserial colonies of Neothoa cf. chiloensis, the weakest bryozoan competitor, were as frequent in central zones as they were in peripheral zones, and usually spread out along channels on the scallop surface. This fugitive species was partially covered by multiserial colonies, but managed to persist even in peripheral areas of the lower valves.

Encrusting bryozoan colonies on stones and algae: variability of zooidal size and its possible causes

This study compared the sizes of zooids in colonies of the cheilostome bryozoanCribrilina annulatacollected from two differing substrata (stones and algae) in three regions of the White and Barents Seas. Zooids of the colonies growing on stones were larger than those in the colonies growing on the thalli of the red algaOdontalia dentata. Size differences of the zooids in the colonies growing on the same substratum in different regions were minor. Three possible explanations for these dimensional differences of zooids are discussed: (1) larvae of different sizes settle on different substrata; (2) ancestrulae of different sizes survive on different substrata; and (3) substrata influence the ancestrulae's size.

Predation on marine bryozoan colonies: taxa, traits and trophic groups

While bryozoans are important components of marine benthic ecosystems, their sig- nificance as food has scarcely been considered in any comparative study. An analysis of the phylo- genetic range of predators on bryozoan colonies was undertaken to elucidate relationships among different consumers. Functional feeding traits and diet categories were determined from literature sources and observations for 399 predator species. Multivariate analyses were used to identify groups of species that consume similar food resources and have related functional traits corresponding to finding, acquiring and ingesting prey. These analyses distinguished gradients among trophic groups based on dissimilar feeding mechanisms, body sizes, types of locomotion and dietary breadths. Co-occurrences of certain diet categories also emerged as important factors. Trophic groups were largely consistent with species clusters at different taxonomic ranks among the predator phyla. At one extreme, fishes and decapod crustaceans with large dietary breadths and body sizes, and crush- ing or tearing feeding mechanisms, appear to consume bryozoans as minor or even incidental parts of their diets. At another extreme, species of nudibranchs, pycnogonids, turbellarians, and certain polychaetes, small arthropods and nematodes that consume bryozoans do so primarily or exclusively. Their body sizes are comparatively smaller and they often have piercing and suctorial feeding mech- anisms. These differences are associated by inference with different probabilities of antagonistic encounters and likelihoods of lethal or sublethal predation. The analyses provide a baseline for eco- logical and evolutionary comparisons, and a broader context for the questions, 'Who eats bryozoans, how, and how frequently?'.

A model explaining some bryozoan colonies

Although the colonialism surely developed independently in Graptolithoidea and Bryozoa, both groups share similar patterns of astogeny. One of the common features is the presence of morphological gradients. Many attempts at its explanation were made for more than a half of the century. This paper discusses a new model of the late astogeny in some bryozoan colonies, showing a cyclic reappearance of secondary zones of astogenetic change and astogenetic repetition that cannot be explained by the single morphogen gradient theory.

A model explaining some bryozoan colonies

AbstractAlthough the colonialism surely developed independently in Graptolithoidea and Bryozoa, both groups share similar patterns of astogeny. One of the common features is the presence of morphological gradients. Many attempts at its explanation were made for more than a half of the century. This paper discusses a new model of the late astogeny in some bryozoan colonies, showing a cyclic reappearance of secondary zones of astogenetic change and astogenetic repetition that cannot be explained by the single morphogen gradient theory.

Borings in trepostome bryozoans from the Ordovician of Estonia: two ichnogenera produced by a single maker, a case of host morphology control

The evolution of borings has shown that the morphology of borings is a function of both the borer and its substrate. This study investigated the effect of bryozoan internal skeletal morphology on the dimensions and distribution of borings. One hundred and forty-three trepostome colonies from the Middle and Upper Ordovician strata of northern Estonia were examined. Of these, 80% were matrix entombed, longitudinally sectioned ramose and hemispherical colonies, and 20% were matrix-free hemispherical colonies that allowed examination of the colony surfaces. Seventy-one percent of the ramose colonies were bored, whereas 88% of the hemispherical colonies were bored. On average, only 8% of colony surface areas were bored out. Borings were more randomly oriented in the hemispherical colonies. In contrast in the ramose colonies, the borings tended to more restricted to the thin-walled endozone and thus parallel to the branch axis. This is interpreted to be a function of the thick-walled exozones controlling to some extent where the borer could bore. Based on morphology, the borings in the hemispherical colonies are referred to Trypanites and those in the ramose colonies to Sanctum . Sanctum is revised to include two possible openings and to recognize that boring shapes were inherently constrained by the thick-walled exozones of the host bryozoan colonies. Both trace fossils were probably produced by a boring polychaete that used the tubes as domiciles. � Estonia, Ichnotaxa, Ordovician, Sanctum, trace fossils, Trypanites.

New celleporid (Bryozoa, Cheilostomata) species from Tertiary deposits of western Kachchh, Gujarat, India

Five new bryozoan species (Buffonellaria cornuta, Lagenipora chedopadiensis, Turbicellepora canui, T. naniberensis andT. rostrata) belonging to the family CelleporidaeHINCKS, 1884 are described and illustrated from the Tertiary sequences of western Kachchh, Gujarat, India. The zoaria of these species comprise about 17 percent of total cheilostome bryozoan colonies from Kachchh in the present collection, and those ofTurbicellepora rostrata n. sp. account for over 64 percent of the celleporid specimens. These records of celleporids enrich our knowledge of the fossil occurrence of this group during the Early Miocene in the Indo-Pacific province.

Sequential development of Buddenbrockia plumatellae (Myxozoa: Malacosporea) within Plumatella repens (Bryozoa: Phylactolaemata)

Colonies of the freshwater bryozoan Plumatella repens collected from a river in the UK were found to be infected with the myxozoan parasite Buddenbrockia plumatellae following laboratory maintenance. Optimisation of the bryozoan diet allowed maintenance of infected colonies for 90 d, permitting observation by light and electron microscopy of the sequential parasitic developmental cycle. Parasite stages were associated with host peritoneum, identifying the primary developmental phase. The association of B. plumatellae cells with peritoneal basal lamina and morphological similarities between parasite and host suggested that the parasite remodelled host tissue. Progressive expansion and elongation of individual parasites led to the release of freely floating vermiform stages within the host coelomic cavities. Within these 'worms', intraluminal masses developed, resulting in the formation of spores. Upon maturation, the 'worms' ruptured, releasing many spores within the host that were subsequently discharged. Although parasitism led to increased bryozoan fragmentation and lowered statoblast production, some colonies did survive, resulting in repeated waves of infection. Long-term laboratory maintenance of infected bryozoan colonies could provide a means of maintaining B. plumatellae for study until the full life cycle is ascertained.

Ecological contrasts across an Antarctic land–sea interface

Abstract We report the composition of terrestrial, intertidal and shallow sublittoral faunal communities at sites around Rothera Research Station, Adelaide Island, Antarctic Peninsula. We examined primary hypotheses that the marine environment will have considerably higher species richness, biomass and abundance than the terrestrial, and that both will be greater than that found in the intertidal. We also compared ages and sizes of individuals of selected marine taxa between intertidal and subtidal zones to test the hypothesis that animals in a more stressed environment (intertidal) would be smaller and shorter lived. Species richness of intertidal and subtidal communities was found to be similar, with considerable overlap in composition. However, terrestrial communities showed no overlap with the intertidal, differing from previous reports, particularly from further north on the Antarctic Peninsula and Scotia Arc. Faunal biomass was variable but highest in the sublittoral. While terrestrial communities were depauperate with low biomass they displayed the highest overall abundance, with a mean of over 3 × 105 individuals per square metre. No significant differences in ages of intertidal and subtidal individuals of the same species were found, with bryozoan colonies of up to 4 years of age being present in the intertidal. In contrast with expectation and the limited existing literature we conclude that, while the Antarctic intertidal zone is clearly a suboptimal and highly stressful habitat, its faunal community can be well established and relatively diverse, and is not limited to short‐term opportunists or waifs and strays.

Colony Structure and Seasonal Differences in Light and Nitrogen Modify the Impact of Sessile Epifauna on the Giant Kelp Macrocystis pyrifera (L.) C Agardh

The presence of the stoloniferous hydroid Obelia geniculata (L.) had no effect on the pigment concentration or nitrogen status of underlying blade tissue of the giant kelp Macrocystis pyrifera (L.) C. Agardh. The sheet-like colonies of the bryozoan Membranipora membranacea (L.) markedly reduced the pigment concentration of colonized blade tissue, but only during winter. Reductions in pigment concentration are most likely a result of damage to underlying tissue due to some factor related to the presence of bryozoan colonies on blade surfaces. Blade tissue colonized by M. membranacea also had higher δ15N signatures than surrounding bryozoan-free tissue, possibly indicating the provision of nitrogen to M. pyrifera by bryozoan colonies. Results show that seasonal changes in nitrogen and colony size can strongly modify the effect of epifauna on macroalgae they colonize. Unlike bryozoans, hydroid colonies provided no barrier to nitrogen uptake by colonized M. pyrifera tissue and enhanced ammonium uptake was observed for tissue colonized by O. geniculata during nitrogen limitation. Epifauna with stoloniferous growth forms such as hydroids are more likely to have benign or even mutualistic relationships with macroalgae they colonize than the sheet-like colonies of bryozoans.

A new Mississippian problematicum from Ireland and Britain: comparison with the problematicum Draffania

Upper Viséan platform limestones from Ireland and northern England contain occasionally hemispherical to bean-shaped structures attached to fenestellid bryozoan colonies. These problematic structures are described and compared with another Mississippian problematicum, Draffania. Both problematic taxa exhibit a similar skeletal structure, but have some different morphological features. They also have comparable stratigraphic records and occupied similar palaeoecological niches. Possible affinities of this new problematicum with foraminiferans, crinoids, algae, and bryozoans are discussed, but its definite taxonomic status remains to be elucidated.