Celleporella Hyalina Research Articles

Epibiotic association of encrusting cheilostome bryozoans on shells of an invasive mussel from rocky shores of South Africa, with the description of a new aviculiferous species of Chaperia

Rocky shores typically exhibit a variety of sedentary and free-moving forms of epibionts associated with the shells of mussel basibionts. This paper provides a first report on epibiotic bryozoans found on shells of the invasive Mediterranean mussel, Mytilus galloprovincialis Lamarck. More than 2500 mussels were collected between December 2019 and October 2020 from rocky shores during low spring tides across the south-southeast coast of South Africa. Ten percent of these mussels hosted epibiotic bryozoans. We examined a subset of these epibiotised mussels to assess the diversity of bryozoans. Three encrusting cheilostome species were identified: Chaperia atypica n. sp., Celleporella hyalina (Linnaeus), and Hippomonavella sp. This new species is the first Chaperia with avicularia and the first South African species with ooecia. This study highlights the biological diversity of epibiotic bryozoans on mussel shells and, given their differences in microtopography, the possibility that invasive species can provide a new substratum for rare, overlooked or undescribed species of epibionts.

Shallow-Water Bryozoan Communities in a Glacier Fjord of West Svalbard, Norway: Species Composition and Effects of Environmental Factors

Despite significant research efforts focused on benthic assemblages in West Spitsbergen, there is a lack of knowledge regarding the shallow water bryozoan communities in Grønfjorden, a glacier fjord belonging to the Isfjorden system, Norway. Here, we studied species composition, richness, distribution, and biomass of bryozoans in the intertidal and upper subtidal zones of Grønfjorden in summer. We found 62 bryozoan species, among which Celleporella hyalina (Linnaeus, 1767), Harmeria scutulata (Busk, 1855), and Tegella arctica (d'Orbigny, 1853) were most prevalent while the highest contributions to the total biomass were registered for Eucratea loricata (d'Orbigny, 1853), Tricellaria gracilis (Van Beneden, 1848), Turbicellepora incrassata (Lamarck, 1816), and Tricellaria ternata (Ellis and Solander, 1786). Alpha-diversity varied from 1 to 50 averaging 15.1 ± 2.6 species. Bryozoan biomass ranged from 0.008 to 10.758 g m-2 with a mean value of 2.67 g m-2 being lower than in the central and northern parts of the Barents Sea. For the first time, we registered the presence of the circumpolar bryozoan Amathia arctica in Svalbard waters probably as a result of stronger advection of Atlantic water into the fjord. Cluster analysis revealed two groups, mainly composed of stations in colder and warmer waters. A relatively high proportion of outlying stations reflected habitat heterogeneity in Grønfjorden. Redundancy analysis indicated that bryozoan diversity and biomass were strongly negatively associated with temperature. A positive relationship was found between bryozoan biomass and the proportional contribution of macrophytes to a pool of substrates. Our study provides a reference point for further monitoring of changing marine ecosystems at high latitudes.

Sexual reproduction of the placental brooder Celleporella hyalina (Bryozoa, Cheilostomata) in the White Sea.

The evolution of parental care is a central field in many ecological and evolutionary studies, but integral approaches encompassing various life‐history traits are not common. Else, the structure, development and functioning of the placental analogues in invertebrates are poorly understood. Here, we describe the life‐history, sexual colony dynamics, oogenesis, fertilization and brooding in the boreal‐Arctic cheilostome bryozoan Celleporella hyalina. This placental brooder incubates its progeny in calcified protective chambers (ovicells) formed by polymorphic sexual zooids. We conducted a detailed ultrastructural study of the ovary and oogenesis, and provide evidence of both auto‐ and heterosynthetic mechanisms of vitellogenesis. We detected sperm inside the early oocyte and within funicular strands, and discuss possible variants of fertilization. We also detail the development and functioning of the placental analogue (embryophore) in the various stages of embryonic incubation as well as embryonic histotrophic nourishment. In contrast to all known cheilostome placentas, the main part of embryophore of C. hyalina is not a single cell layer. Rather, it is a massive “nutritive tissue” whose basal part is associated with funicular strands presumably providing transport function. C. hyalina shows a mixture of reproductive traits with macrolecithal oogenesis and well‐developed placenta. These features give it an intermediate position in the continuum of variation of matrotrophic provisioning between lecithotrophic and placentotrophic cheilostome brooders. The structural and developmental differences revealed in the placental analogue of C. hyalina, together with its position on the bryozoan molecular tree, point to the independent origin of placentation in the family Hippothoidae.

Recruitment of benthic invertebrates in high Arctic fjords: Relation to temperature, depth, and season

AbstractIn the high Arctic, recruitment of hard‐bottom benthic organisms has been studied at single locations, but little is known about how it varies spatially or temporally, or how it is influenced by abiotic factors. In this study, settlement plates were simultaneously deployed at five locations in three Svalbard (Norway) fjords at depths ranging from 7 m to 215 m. Recruitment was significantly different among fjords and among locations within a fjord. Recruits at each site co‐occurred randomly even though interspecific overgrowth was observed. This finding provides further evidence that there is not necessarily a relationship between non‐random co‐occurrence and interspecific competition, such as is traditionally assumed for other isolated, island‐like habitats. We found significantly lower recruitment in an Arctic‐influenced fjord than in more Atlantic‐influenced fjords. The abundance and richness of recruits was significantly lower in fall‐winter than in spring‐summer, but the spirorbid Circeis armoricana recruited in high abundance in fall‐winter. Both the abundance and taxonomic richness of recruits declined exponentially with depth, with the hydroid Stegopoma plicatile dominating at 215 m in an Atlantic‐influenced fjord. The most abundant recruiting taxa (C. armoricana, Semibalanus balanoides, Harmeria scutulata, Celleporella hyalina) can be described as pioneer (early‐succession) species. Crustose coralline algae, a slow‐growing superior competitor, also recruited at one location. Recruitment in Svalbard is highly variable, both spatially and temporally, and our results show the influence of local factors such as adult species composition.

Intertidal Bryozoa from Korea-new additions to the fauna and a new genus of Bitectiporidae (Cheilostomata) from Baengnyeong Island, Yellow Sea.

Eight species are added to the intertidal bryozoan fauna of South Korea, all collected from the extreme northwestern part of the country at Baengnyeong Island. Five of the species (Hippothoa imperforata, Celleporella hyalina, Celleporella nodasakae, Porella donoghueorum and Suhius rubescentis) are new records. Cauloramphus dicki n. sp., Cauloramphus spencerjonesae n. sp., and Exochella cryptodontia n. sp. are new to science; Suhius n. gen. is a newly recognized genus in Bitectiporidae. The close morphological similarity of umbonuloid-shielded P. donoghueorum to Australasian and Antarctic species of lepralioid-shielded species of Aimulosia is discussed in relation to ascophoran phylogeny. The described cheilostome fauna from South Korea is herein increased to 121 species.

Molecular variability in the Celleporella hyalina (Bryozoa; Cheilostomata) species complex: evidence for cryptic speciation from complete mitochondrial genomes

The bryozoan Celleporella has been shown to be composed of multiple, often cryptic, lineages. We sequenced two complete mitochondrial (mt) genomes of the Celleporella hyalina species complex from Wales, UK and Norway (i) to determine genetic divergence at the complete mt genome level, and (ii) to design new molecular markers for examining the interrelationships amongst the major lineages. In addressing (i), we estimated genetic divergence at three levels: (a) nucleotide diversity (π), (b) genome size, and (c) gene order. Genes nad4L, nad6, and atp8 showed the highest levels of divergence, and rrnL, rrnS, and cox1 showed the lowest levels. Inter-genome nucleotide divergence of protein-coding and ribosomal RNA genes, measured as π, was 0.21. The two genomes differed substantially in size, with the Norwegian genome being 2,573 base pairs (bp) longer than the Welsh genome, 17,265 and 14,692 bp, respectively. This difference in size is attributable to long non-coding regions present in the Norwegian genome. Both genomes exhibit similar gene orders, except for the translocation of one transfer RNA (trnA). Considering the high nucleotide diversity, genome size difference and change in gene order, these mt genomes are considered sufficiently divergent to have originated from two distinct species. In addressing (ii) we designed PCR primers that flank the most conserved regions of the genome: 1,300 bp of cox1 and a contiguous 2,000 bp fragment of rrnL + rrnS. The primers have yielded products for tissue from Wales, Norway, New Zealand, Alaska and Chile and should provide useful tools in establishing species- and population-level diversity within the Celleporella complex.

Will variation among genetic individuals influence species responses to global climate change?

Increased anthropogenic CO2 emissions in the last two centuries have lead to rising sea surface temperature and falling ocean pH, and it is predicted that current global trends will worsen over the next few decades. There is limited understanding of how genetic variation among individuals will influence the responses of populations and species to these changes. A microcosm system was set up to study the effects of predicted temperature and CO2 levels on the bryozoan Celleporella hyalina. In this marine species, colonies grow by the addition of male, female and feeding modular individuals (zooids) and can be physically subdivided to produce a clone of genetically identical colonies. We studied colony growth rate (the addition of zooids), reproductive investment (the ratio of sexual to feeding zooids) and sex ratio (male to female zooids) in four genetically distinct clonal lines. There was a significant effect of clone on growth rate, reproductive investment and sex ratio, with clones showing contrasting responses to the various temperature and pH combinations. Overall, decreasing pH and increasing temperature caused reduction of growth, and eventual cessation of growth was often observed at the highest temperature, especially during the latter half of the 15‐day trials. Reproductive investment increased with increasing temperature and decreasing pH, varying more widely with temperature at the lowest pH. The increased production of males, a general stress response of the bryozoan, was seen upon exposure to reduced pH, but was not expressed at the highest temperature tested, presumably due to the frequent cessation of growth. Further to the significant effect of pH on the measured whole‐colony parameters, observation by scanning electron microscopy revealed surface pitting of the calcified exoskeleton in colonies that were exposed to increased acidity. Studying ecologically relevant processes of growth and reproduction, we demonstrate the existence of relevant levels of variation among genetic individuals which may enable future adaptation via non‐mutational natural selection to falling pH and rising temperature.

Patterns of self compatibility, inbreeding depression, outcrossing, and sex allocation in a marine bryozoan suggest the predominating influence of sperm competition

Sex allocation by simultaneous hermaphrodites is theoretically influenced by selfing rate, which is in turn influenced by the benefits of enhanced genomic transmission and reproductive assurance relative to the cost of inbreeding depression. The experimental investigation of these influences in seed plants has a rich pedigree, yet although such an approach is equally relevant to colonial invertebrates, which globally dominate subtidal communities on firm substrata, such studies have been scarce. We reared self-compatible genets of the marine bryozoan Celleporella hyalina s.l. in the presence and absence of allosperm, and used molecular genetic markers for paternity analysis of progeny to test theoretical predictions that: (1) genets from focal populations with high selfing rates show less inbreeding depression than from focal populations with low selfing rates; (2) genets whose selfed progeny show inbreeding depression prefer outcross sperm (allosperm); and (3) genets bias sex allocation toward female function when reared in reproductive isolation. Offspring survivorship and paternity analysis were used to estimate levels of inbreeding depression and preference for outcrossing or selfing. Sex allocation was assessed by counting male and female zooids. As predicted, inbreeding depression was severe in selfed progeny of genets derived from the populations with low self-compatibility rates, but, with one exception, was not detected in selfed progeny of genets derived from the populations with higher self-compatibility rates. Also, as predicted, genets whose selfed progeny showed inbreeding depression preferred outcrossing, and a genet whose selfed progeny did not show inbreeding depression preferred selfing. Contrary to prediction, sex allocation in the majority of genets was not influenced by reproductive isolation. Lack of economy of male function may reflect the over-riding influence of allosperm-competition in typically dense breeding populations offering good opportunity for outcrossing. We suggest that hermaphroditism may be a plesiomorphic character of the crown group Bryozoa, prevented by phylogenetic constraint from being replaced by gonochorism and therefore not necessarily adaptive in all extant clades. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 519–531.

Mitochondrial DNA phylogeography and mating compatibility reveal marked genetic structuring and speciation in the NE Atlantic bryozoan Celleporella hyalina

The marine bryozoan Celleporella hyalina is a species complex composed of many highly divergent and mostly allopatric genetic lineages that are reproductively isolated but share a remarkably similar morphology. One such lineage commonly encrusts macroalgae throughout the NE Atlantic coast. To explore the processes leading to geographical diversification, reproductive isolation and speciation in this taxon, we (i) investigated NE Atlantic C. hyalina mitochondrial DNA phylogeography, and (ii) used breeding trials between geographical isolates to ascertain reproductive isolation. We find that haplotype diversity is geographically variable and there is a strong population structure, with significant isolation by distance. NE Atlantic C. hyalina is structured into two main parapatric lineages that appear to have had independent Pleistocene histories. Range expansions have resulted in two contact zones in Spain and W Ireland. Lineage 1 is found from Ireland to Spain and has low haplotype diversity, with closely related haplotypes, suggesting a recent population expansion into the Irish Sea, S Ireland, S England and Spain. Lineage 2 is found from Iceland to Spain and has high haplotype diversity. Complete reproductive isolation was found between some geographical isolates representing both lineages, whereas it was incomplete or asymmetric between others, suggesting these latter phylogeographical groups probably represent incipient species. The phylogeographical distribution of NE Atlantic C. hyalina does not fall easily into a pattern of southern refugia, and we discuss likely differences between terrestrial and marine system responses to Pleistocene glacial cycles.

From cells to colonies: at what levels of body organization does the ‘temperature‐size rule’ apply?

An inverse relationship between temperature during ontogeny and final body size is widespread in ectotherms, but poorly understood. Evidence suggests that within organs, this "temperature-size rule" (TSR) may also apply to cell size with no change in numbers. So how closely do reductions in size and number of cells and other repeated structures correlate with size reduction at higher levels of organization? We examine this in the context of a proposal that size and/or number changes at various organizational levels are adaptive responses to temperature- and size-dependent oxygen supply. We subjected two clones of the modular colonial bryozoan, Celleporella hyalina, to orthogonal combinations of two temperatures and two oxygen concentrations during ontogeny, observing effects on sizes of colonies and larvae, and sizes and numbers of cells, tentacles, and modules (autozooids). We found that the size:number responses varied among cell types and among structures at different levels of organization, with the inverse temperature-size relationship applying only to larval parenchymal cells and colony modules. Using our findings and other evidence we propose a unifying adaptive hypothesis that predicts how temperature affects the sizes of mitochondria, cells, organs, modules and organisms, and their relationships with processes that determine the functional capacity of aerobic metabolism.

Substratum as a structuring influence on assemblages of Arctic bryozoans

The nature of the substratum is a fundamental factor determining the types of organisms and communities found in many terrestrial and benthic habitats. The extent to which this is true in extreme environments was investigated using bryozoan assemblages as model organisms in an Arctic fjord (Kongsfjorden 79°N, 12°E) in summer 2001 using SCUBA. Twenty-seven substrate samples of 0.25 m2 were taken at 10 m depth from the inner glacial basin to the mouth of the fjord. Multivariate analyses revealed four different bryozoan assemblages. The sea floor of the inner basin of Kongsfjorden near the glacial fronts was characterized by low diversity and dominance of the ctenostome species Alcyonidium disciforme Smitt. Highest richness and diversity occurred on rock substratum with mean size >10 cm2, on which the most common species was the pioneer Harmeria scutulata Busk (abundance: 15%). On smaller rocks with mean size <2 cm2, the runner-like pioneer species Electra arctica Borg comprised most individuals of the assemblage (98%). Yet another pioneer, Celleporella hyalina Linnaeus, was the most abundant species (49%) on substratum dominated by algae. Thus, in each habitat type, pioneers dominated but different species and to different extents. There was much variation in species composition and abundance within assemblages of heterogeneous habitats, and this study emphasizes the importance of microhabitats and physical conditions. Heterogeneity was evident at scales of <1 m.

Composition of bryozoan assemblages related to depth in Svalbard fjords and sounds

Svalbard bryozoan communities were investigated along a depth range from the surface to 296 m between the inner glacial fronts and fjord mouths during 2001 and 2002. The main study area was Kongsfjorden (79°N, 12°E). A total of 137 taxa of bryozoans were identified: 108 to species, 24 to genus, 3 to family, 1 to order and 1 to phylum level. Cluster and multidimensional scaling analyses revealed four distinct assemblages of bryozoans: shallow (0–40 m; 68 taxa), deep (40–296 m; 80 taxa), inner fjordic (three taxa) and an assemblage found on small stones in shallow waters (nine taxa). The inner fjordic assemblage was recorded from the front of tidal glaciers extending about 10 km out into the fjord. In terms of abundance, Celleporella hyalina Linnaeus dominated in shallow areas (18%), Hippothoa arctica Kluge (55%) in deep water, Alcyonidium disciforme Smitt (86%) proximate to glaciers fronts and Electra arctica Borg on small stones (98%). The species were classified according to their depth range as a stenobathic-shallow (46 taxa), stenobathic-deep (57 taxa) and eurybathic-generalist (21 taxa). Mean diversity measures did not show any significant differences between the shallow and deep communities. The bryozoan assemblages seem to be structured primarily by processes related to depth and sediment characteristics.

Kin or self‐recognition? Colonial fusibility of the bryozoan Celleporella hyalina

We estimated fusion frequency with respect to coancestry in the bryozoan Celleporella hyalina, whose briefly planktonic sexually produced larvae settle on algal substrata and proceed to form encrusting colonies by iterative budding. Frequency of fusion between paired colonies growing on an artificial substratum was positively correlated with coefficient of relatedness, with allorecognition ability increasing during the early stages of colonial growth after larval settlement. Parents repressed the growth of F1 progeny with which they had fused. The results are concordant with the Feldgarden-Yund model of selection for self-recognition, which regards fusion with kin as an inevitable source of error whose cost diminishes with increasing relatedness. Contrary to fusion compatibility, gametic compatibility is negatively correlated with coancestry, indicating a need for further research on the possibility of common or linked genetic control that has opposite effect at somatic and gametic levels.

Female investment is retarded pending reception of allosperm in a hermaphroditic colonial invertebrate.

Young colonies of the bryozoan Celleporella hyalina are capable of acquiring water-borne allosperm and of using it to fertilize ova for a period of 3-6 weeks after reaching female sexual maturity. In these simultaneous hermaphrodites, early allocation to female modules, but not male, is greatly enhanced by the acquisition of allosperm. The degree of enhancement is inversely proportional to coancestry of the recipient and donor colonies, thus promoting outcrossing. This apparently novel mechanism of adjusting operational sex ratio depends on the uptake and storage of sperm by nonreproductive (somatic) modules and subsequent translocation to females.

Colony growth rate of encrusting marine bryozoans ( Electra pilosa and Celleporella hyalina)

Growth experiments were performed in a strong current environment (Menai Strait, UK) with cloned, transplanted colonies of encrusting Electra pilosa and Celleporella hyalina growing on microscope slides mounted on a raft. Colony growth was also recorded for the same species, both appearing naturally on macroalgae and in controlled laboratory experiments. For the laboratory experiments, the lowest algal concentration that still resulted in maximum growth rate (about 0.07 day −1) for E. pilosa was at most 1500 Rhodomonas cells ml −1, corresponding to 1.9 μg chl a l −1, close to but greater than the mean value measured in the Menai Strait. For the raft experiments, colonies were exposed to naturally occurring fast flow (about 40 cm s −1) and to reduced flow (about 30 cm s −1). The mean phytoplankton concentration was 1.1±0.6 μg chl a l −1, and the specific growth rate was 0.10–0.12 day −1, regardless of species and flow regime. The somewhat slower growth of natural bryozoan colonies on macroalgae (0.08 day −1) may be due to their larger initial size. Based on estimates of the thickness of the viscous sublayer it is concluded that suspension feeding by encrusting bryozoans may be restricted to the viscous sublayer, and that increasing current velocities do not reduce the growth (and thus feeding).

Inbreeding and hermaphroditism in the sessile-brooding bryozoan Celleporella hyalina

This study examined the occurrence and effects of inbreeding in the sessile, colonial hermaphrodite Celleporella hyalina. The results are discussed with regard to theoretical explanations for the prevalence of hermaphroditism in sessile clonal organisms. C. hyalina exhibited inbreeding depression at all stages, including the pre-zygotic. Outcrossing, sib and half-sib matings produced offspring but selfing did not. There was inbreeding depression in embryo production and survival. Inbred colonies showed slower growth and later maturation, with fewer reproductive zooids. The relative numbers of male and female zooids were affected by inbreeding; increased production of males is a sign of stress in C. hyalina. When mated with an outbred non-relative, inbred colonies had lower success both as males and as females in embryo production and offspring survivorship. The low survivorship of embryos fathered by inbred colonies is a clear effect of inbreeding on the F2 generation. These results indicate that C. hyalina is unlikely to inbreed in the wild, supporting the "space-limited" model of hermaphroditism for this species. This study indicates that hermaphroditism, by avoiding much of the cost of sex, can confer optimal reproductive fitness for sessile brooding animals in a space-limited habitat even in the absence of inbreeding.

Molecular Phylogeography of the Cosmopolitan Bryozoan Celleporella hyalina: Cryptic Speciation?

2 Knowlton (1993) has argued that the failure to recognize cryptic species in the marine environment has crippled ecological and evolutionary understanding of the oceans. This failure is due partly to the comparative lack of study of this environment; a much smaller fraction of marine taxa have received genetic characterization than is true for land organisms. The sessile hippothoid bryozoan Celleporella hyalina is a clonal, colonial invertebrate which encrusts macroalgae and other substrata in the intertidal zone. It is distributed circumglobally in the temperate waters of both hemispheres. Classification of the Hippothoidae has been much discussed (Ryland and Gordon, 1977; Hastings, 1979; Ryland, 1979; Morris, 1980; Moyano and Gordon, 1980), but the general use of morphological differences alone to classify bryozoans has been criticized (Levinton et al., 1991) and there is thought to e a considerable frequency of cryptic or sibling species mong widespread bryozoan taxa (Lidgard and Buckey, 1994). Much more needs to be known about phyloenetics, reproductive interactions, and the influence f phenotypic plasticity before complete confidence can e placed in current classifications. Small differences n morphology are still being used in the description of ew species of Celleporella (e.g., Cesar-Aldariz et al., 999). The phylum Bryozoa has received very little moleclar genetic study. Preliminary investigations of C. yalina indicated that there may be isolation by disance within this cosmopolitan species. Microsatellites aised on Welsh C. hyalina failed to give PCR products or Swedish, Atlantic American, or Chilean individuals Hoare et al., 1998). RAPD profiles also indicated that . hyalina from Wales and Chile were divergent (Goldon, 1998). These preliminary studies indicated that ritish C. hyalina differed from other populations and

Age-dependent loss of fertility in water-borne sperm of the bryozoan Celleporella hyalina

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 224:87-92 (2001) - doi:10.3354/meps224087 Age-dependent loss of fertility in water-borne sperm of the bryozoan Celleporella hyalina P. H. Manríquez1, R. N. Hughes1,*, J. D. D. Bishop2,3 1School of Biological Sciences, University of Wales, Bangor, Gwynedd LL57 2UW, United Kingdom 2Marine Biological Association of the UK, The Laboratory, Citadel Hill, Plymouth PL1 2PB, United Kingdom 3Department of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, United Kingdom *Corresponding author. E-mail: r.n.hughes@bangor.ac.uk ABSTRACT: The cheilostome bryozoan Celleporella hyalina (L.) was used as a model to test the hypothesis that sessile animals fertilising retained eggs by water-borne sperm should produce sperm with relatively prolonged fertility during the dispersal phase. Ramets of each of several recipient clones were exposed to suspensions of allosperm obtained by induced release from ramets of donor clones. Allosperm was presented to each series of ramets at a concentration of 10 to 102 ml-1, in aliquots of increasing age after release. Control ramets of the recipient clones isolated from allosperm failed to produce embryos, indicating the absence of autogamy. Experimental ramets exposed to fresh allosperm copiously produced embryos, but the frequency of embryos declined sharply in ramets exposed to allosperm suspension of increasing age. The estimated fertile half life of water-borne sperm was 1.2 h, which is at the upper limit of the range of values reported for other marine animals at comparable concentration. C. hyalina maximises fertilisation success by efficient dissemination, capture and storage of relatively long-lived sperm. KEY WORDS: Free-spawning · Allosperm · Allogamy · Sperm storage · Cloning Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 224. Online publication date: December 18, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.

Seasonality of Competition in Early Development of Subtidal Encrusting Communities

Abstract. Settlement panels immersed at Lough Hyne, County Cork, Ireland, at six stations with widely different flow regimes were retrieved at monthly intervals. Between 40 and 62 taxa were identified at each station during the study period. Percentage cover, number of interactions and number of recruits were recorded. Space occupied was found to vary more than 2.5 orders of magnitude between stations and seasons (0.3 – 82 %). Competition for space was most intense during summer, when recruitment was highest. More than 3600 interactions between pairs of species were recorded and competitive matrices are presented for the two stations with the most interactions. Both number of interactions and % cover were significantly higher at sites with greater water flow. The nature and the degree of competition varied between sites, with the most intense competition occurring in the very high flow sites with a large proportion of intra­specific encounters. Colonial species were more evident at the sites with high flow. Certain solitary species (notably Anomia ephippium and Pomatoceros spp.) were successful competitors in encounters with cheilostomatid bryozoans. Solitary species may prevent space monopolisation by the faster‐growing bryozoans. ‘Typical’ early successional species, notably bryozoans such as Celleporella hyalina and Microporella ciliata, were more abundant at the more disturbed sites, implying either a larger adult population and/or preferential settlement of these species at such sites.

Molecular genetic evidence for the prevalence of outcrossing in the hermaphroditic brooding bryozoan Celleporella hyalina

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 188:73-79 (1999) - doi:10.3354/meps188073 Molecular genetic evidence for the prevalence of outcrossing in the hermaphroditic brooding bryozoan Celleporella hyalina K. Hoare*, R. N. Hughes, A. J. Goldson Brambell Building, School of Biological Sciences, University of Wales, Bangor, Gwynedd LL57 2UW, Wales, UK *Present address: School of Ocean Sciences, University of Wales Bangor, Menai Bridge, Gwynedd LL59 5EY, Wales, UK. E-mail: kh@fferal.freeserve.co.uk ABSTRACT: The occurrence of inbreeding was investigated in Celleporella hyalina, which has been reported as being capable of selfing. In total, 4 tetranucleotide microsatellite markers were scored in populations from sites within the Menai Strait (Wales) and the Yealm Estuary (Plymouth, England). All loci in all populations were in Hardy-Weinberg equilibrium, with insignificant Fis values, which indicates that C. hyalina in these populations generally outbreed. No significant differences were found between populations up to 8 km apart, indicating sufficient gene flow on this scale to form a single breeding population despite geographic separation. The Plymouth population was significantly (p < 0.00001) deviant from the others, indicating possible isolation by distance at the scale of 900 km. C. hyalina cultured in the laboratory were observed to spawn sperm into the surrounding seawater. Sib larvae were found to settle randomly with respect to each other. In isolation C. hyalina failed to produce offspring, though a small proportion brooded abortive embryos. Pairings between individuals of differing genotypes resulted in the production of offspring, all of which, when genotyped with respect to the parent colonies, were found to be the result of outcrossing. KEY WORDS: Inbreeding · Fertilisation · Outcrossing · Sibs · Genetics · Bryozoan · Celleporella Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 188. Publication date: November 03, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.