A new species of Ophlitaspongia (Porifera: Microcionidae) from wave-exposed sublittoral rock in the north-east Atlantic is described and compared to the two other species recorded from the genus in the north-east Atlantic. The species known as Ophlitaspongia seriata is considered to be a junior synonym of Halichondria panicea. Consequently, the name O. papilla has been reinstated. The other recorded species O. basifixa, is from deep water. Ophlitaspongia basifixa has characters which differentiate it from Ophlitaspongia sp. nov. The genus Ophlitaspongia has been separated from related genera and reinstated for species in the North Atlantic.

The bibliography concerning the Mediterranean Sipuncula is reviewed, particularly that from the eastern Mediterranean. Additional data are provided from macrobenthic samples collected between 1974 and 1997 in the Hellenic waters. A total of 17 species are recorded, five of which (Sipunculus norvegicus, Golfingia elongata, Nephasoma lilljeborgi, Thysanocardiacatharinae and Aspidosiphon (Akrikos) mexicanus) are reported for the first time in Hellenic waters. Three more species (Onchnesoma squamatum squamatum, Aspidosiphon (Aspidosiphon) elegans, Apionsoma (Apionsoma) trichocephalus) which are found exclusively in the extreme eastern basin (Israel, Egypt) raises the number of eastern Mediterranean Sipuncula species to twenty.

Two strains of 6–8-y old Actinia equina (Anthozoa: Actiniaria) asexually derived from two individuals collected on the coast of Brittany were artificially UV irradiated in long-term experiments in the laboratory. After the animals had been allowed to adjust to the test aquaria for 15 months, a programme of UV irradiation and multiparameter analysis continued for 24 months. Ultraviolet irradiated sea anemones obtained in addition a quasi-solar UV irradiation at intensities representing the daily and annual cycles. Of the three modes of UV irradiation tested (1X, 2X and 4X), the one with the lowest intensity and duration (1X) corresponded approximately to the irradiation to which sea anemones are exposed in their natural habitat in the tidal zone of the southern North Sea. In all three modes all the actinians showed a similar, highly significant quasi-exponential weight loss immediately after the onset of UV irradiation. The more the animals were irradiated, the later juveniles were released from the gastrovascular cavity. At 2X the number of active animals gradually decreased after 18 months, whereas with the 4X irradiation mode the amount of activity fell abruptly and significantly after only eight months and remained at a very low level. Detachment from the substrate was also induced by UV irradiation. The experiments showed genotype-specific differences in body mass and migration. The crucial findings were that A. equina individuals that had adjusted to the laboratory for a long time did give clear responses to UV doses and intensities corresponding approximately to the irradiation in their natural intertidal environment or by radiation increased severalfold. The responses were immediate and sometimes irreversible to UV even in naturally occurring intensities and doses. The genotype specificity of some responses provides evidence that the stressor UV could induce genetic modifications of the population.

While it is generally assumed that jellyfishes (Cnidaria: Scyphozoa) are stably tetramerous, variation in symmetry (i.e. unimerous to octamerous) can be observed in most populations at a rate of approximately 2%, but sometimes as high as 10%. This type of variation has been observed among clonemates during strobilation in five taxa, namely Aurelia aurita, A. labiata, Chrysaora fuscescens, Pelagia colorata, and Phacellophora camtschatica. It is currently unclear whether the symmetry variation is caused by genetic, environmental, or developmental factors, or some combination. Although hexamerous lineages were not bred successfully, lineages were raised with rates of variation higher than normal. Thus, there may be some genetic component to the variation. In one lineage observed over 4.5 months, the rate of non-tetramery declined substantially from an initial high of 88.9% to a final cumulative low of 29%. Apparently this lineage was able to stabilize tetramery over time, possibly indicating some self-correcting developmental mechanism. Furthermore, no difference was found in variation rates between stressed and unstressed polyps, indicating that environmental factors may not play an important role in symmetry determination in these animals. These results indicate stabilizing selection in controlling the expression of variable symmetry.

A new species of the genus Celleporella (Celleporella galaica sp. nov.) is described from material collected in Galicia (north-west Spain).

Heteroxenia fuscescens is a common zooxanthellate soft coral on the shallow reefs of the Gulf of Eilat, northern Red Sea. Its main nutritional sources are the uptake of dissolved organic material (DOM) and carbon fixation by its symbiotic algae (zooxanthellae). Recent studies have indicated that although colonies of H. fuscescens release planulae all year round, their fecundity was subject to seasonal changes. In this study the monthly per cent of ash, lipid, protein and carbohydrate in the coral tissue over a three year period was determined. It was found that the tissues of colonies of H. fuscescens contained a monthly per cent mean of 8.8±4 ash (without sclerites), 11±3.5 lipid, 19.2±6.4 protein, and 0.6±0.01 carbohydrate (N=36). This study is the first to present such values based on long term investigation of the biochemical profile of a coral, thus enabling an examination of temporal variability in biochemical composition among seasons and successive years. The results indicated seasonal fluctuations in lipid and protein content, while variation in the biochemical composition among years was expressed only in the protein content. The mean energetic content of H. fuscescens was relatively high at 23.3±1.2 kJ g−1 dry weight (DW). A significant difference in the energetic content of H. fuscescens was found among seasons. It is suggested that the increase in nutrient levels following the annual mixing event at the Gulf of Eilat and the raised light levels led to high energetic content during summer, which may reflect the increase in the number of embryos and developing planulae in H. fuscescens colonies. Furthermore, it is suggested that in the Gulf of Eilat seasonal fluctuations in the abiotic features of the water may have an impact on the biochemical composition and energetic content of the studied species.

A total of 13 boring species of spionid polychaetes were extracted from 28 different calcareous substrata (i.e. mollusc shells, coralline algae and barnacle tests) from Japan. The spionids were: seven Polydora spp.: Polydora brevipalpa, P. websteri, P. curiosa, P. uncinata, P. aura, P. glycymerica, Polydora sp; five Dipolydora spp.: Dipolydora concharum, D. bidentata, D. alborectalis, D. giardi, D. armata; and one Carazziella sp.: Carazziella reishi. All of them inhabited self-excavated burrows in living and/or migratory calcareous substrata and they were never found from soft sediments. Burrow structures were species-specific. The Polydora species basically excavated simple U-shaped burrows, while the Dipolydora species excavated more varied, distinct burrows. The boring activity seemed species-specific among polydorids. This study attempts to summarize and discuss the biological characteristics of these boring species inhabiting Japan. In addition, P. curiosa, P. glycymerica, Polydora sp., D. giardi and C. reishi are new to Japan.

The influence of various species of digenean trematodes on the in situ growth rate of Littorina littorea (Gastropoda: Prosobranchia) from different habitats was investigated. The main results showed: (1) that infections either reduced or had no significant effect on growth in comparison with uninfected snails; (2) that the same type of infection could have a differential effect on growth depending on the habitat/population from which the snails originated. These findings are consistent with the life history hypothesis expecting no or a stunting effect of trematode infections on the growth of longer-lived snails, but do also emphasize that growth rates following trematode invasion can be significantly modified by environmental conditions, such as, food availability.

Two barnacle species (Semibalanus cariosus and Chthamalus challengeri) were studied during two years at Hokkaido, northern Japan, to find the interspecies boundary and to determine whether interspecific competition (interference and pre-emption) is important in maintaining the zonation in our study system. Both barnacle species showed tide level dependent distribution patterns in the boundary zone. Semibalanus cariosus was dominant at lower levels; this pattern was determined by post-recruitment mortality. This mortality pattern seemed to be set by physical stress because recruitment density and survival rate were not correlated with the cover of other species, and mortality was higher in higher zones where physical stress is more severe. Chthamalus challengeri was dominant at higher levels; this pattern was determined by recruitment. The recruitment density and survival rate of this species were not affected by the covers of other species, thus, neither interference nor pre-emption significantly affected the distribution pattern. Interspecific competition appears to be less important in organizing barnacle communities in our study area than in previously studied areas, however, the recruitment process is of major importance.

In October 1994, 39 macrobenthic samples, divided between two areas, were taken on the western Belgian Coastal Banks. The two areas could not be clearly divided, concerning their macrobenthic communities. Multivariate techniques revealed five coherent communities, linked with typical sedimentological factors: (1) the Barnea candida community in a very compact muddy sediment (median 14 μm); (2) a second community characterized by the presence of spat of Mytilus edulis, with a medium sandy sediment (median 456 μm); (3) the Lanice conchilega community inhabiting a fine sandy sediment (median 211 μm); (4) the Nephtys cirrosa–Echinocardium cordatum community in a coarser fine sandy sediment (median 242 μm); and (5), closely related to the latter, the N. cirrosa community also occurring in a fine sandy sediment (median 224 μm). Only the L. conchilega community belongs to the diverse transition zone. The other four communities seem to be part of the heterogeneous, species-poor coastal zone associations. No open sea communities have been detected in the area.

On the western Coastal Banks only the L. conchilega community, because of the high numbers of Abra alba, Tellina fabula, and Spisula subtruncata, can be interesting as feeding grounds for the common scoter (Melanitta nigra (Aves: Mergini)). Comparison of the spatial distribution of the wintering common scoters and the L. conchilega community revealed no direct similarity. The factors possibly causing this dissimilarity have been discussed.

Nematode species from three intertidal assemblages (St Lawrence Estuary, Quebec, Canada) were studied in order to form an ecological interpretation of three allometric attributes: body width, size spectra, and morphotypes. The three assemblages were characterized by a very similar sediment grain median (Md) but different silt–clay proportions: A1 (upper-tidal level; Md=122 μm; silt=34.8%), A3 (mid-tidal level; Md=182 μm; silt=12.8%), and A5 (lower-tidal level; Md=122 μm; silt=6.8%). Silt–clay proportions were an influential factor in determining the mean nematode body width, used as a morphological discriminant between burrowing and interstitial organisms. A plot of the number of species vs the body width-classes showed two peaks: between 19.3 and 22.6 μm (interstitial), and between 32.0 and 45.5 μm (burrowers). As for the size spectra, in sandy sediments the mean nematode individual biomass was smaller than in muddy sediments. As a consequence, the estimated mean individual respiration rate was greater in muddy (A1=2.26 nl O2 h−1) than sandy sediments (A3=1.25 nl O2 h−1; A5=1.12 nl O2 h−1). In contrast, estimated metabolic ratios were lower in A1 (2.78 nl O2 h−1 μg−1 dry weight, DW) than in A3 (2.95 nl O2 h−1 μg−1 DW) and A5 (3.01 nl O2 h−1 μg−1 DW) suggesting different productivity and/or physiological adaptations to different lifestyles (burrowing vs interstitial) between species inhabiting muddy or sandy sediments. Morphotypes (body width/body length ratio=w/l ratio) were found to be associated with feeding groups. Small w/l ratios were typical of microvores, while greater ratios were typical of epigrowth feeders and predators. Ciliate-feeders, deposit-feeders and facultative predators had intermediate ratios. A morphotype food-related hypothesis is proposed: the species morphotype reflects the quality of exploited food; a small w/l ratio (i.e. long gut) would favour digestive efficiency and would be an adaptation to low quality food (microvores); inversely, a greater w/l ratio (i.e. short gut) would be an adaptation to high quality food (epigrowth-feeders and predators).

Microhabitat use by nine species of caprellid amphipods in the genus Caprella inhabiting a Japanese Sargassum bed could be divided into three major categories. Differences in the patterns of use were closely related to the nature of the mother–young association and morphological characteristics of young. Pattern A was shown by three species Caprella danilevskii, C. okadai and C. subinermis that produced large first instar young (>1.6 mm in body length, BL) with no maternal care, and directly use Sargassum thalli as habitat substrata throughout their lives. Two different patterns of microhabitat use occur in the six other species, which produce small first instar young (<1.3 mm BL) and have trouble using Sargassum thalli as their primary habitat. Pattern B comprised of C. decipiens, C. monoceros and C. scaura in which females care for their young until they become large enough to disperse onto the seaweed thalli. The first instar young of these three maternal care species have specialized pereopods. In Caprella monoceros and C. scaura, which show a ‘cling-to-mother’ type of maternal care, each pereopod has a concaved margin on the propodus and a long dactylus, well adapted for clinging to the mother, and C. decipiens, which show a ‘stay-around-mother’ type of maternal care, have comparatively slender and longer pereopods to hold onto seaweed branches near their mother. Pattern C included C. arimotoi, C. glabra and C. penantis which showed no maternal care and use thin branches of epizoites such as epiphytic hydroids as their primary substrata. It is concluded that caprellids that live on seaweed with thick thalli and branches such as Sargassum patens have different solutions to the problem of where the small first instar young can live: species with larger young emerge directly onto seaweed thalli, but species with smaller young use an epiphytic secondary habitat or depend on maternal care.

In this study the digenean parasites in the mud snail Hydrobia ulvae at two sites were compared for a period of one year. The sites were the north shore of Belfast Lough (Northern Ireland) and the Bend of Tarty on the Ythan Estuary (north-east Scotland). Samples of snails were collected monthly from which 13 species of digenean larvae were recorded at Belfast Lough. Two of these species were absent at the Bend of Tarty. Overall digenean prevalence was very similar at each site indicating that the respective bird communities were composed of ecologically equivalent species. Differences in the prevalence of individual digenean species are discussed in relation to the abundance of definitive and/or secondary intermediate hosts at each of the sites. Both sites displayed similar seasonal patterns of parasite prevalence with sharp increases to around 25% in the summer months. Snail shell heights were greater at Belfast Lough than at the Bend of Tarty and a positive correlation between snail shell height and infection by trematode parasites was recorded at both sites. Increased parasite prevalence in larger snails was attributed to factors such as age-related susceptibility and/or parasitic castration of the snails.

Nematode assemblages were sampled seasonally at three subtidal stations along the Belgian coast. The stations were characterized by muddy sediments (station 115), fine sand (station 702) and fine to coarse sand (station 790). The forces structuring vertical distribution were investigated by evaluating abundance, species composition, diversity and trophic composition, and relating these to sediment composition, redox state and food sources.

The nematode assemblages at the two finer grained stations (115, 702) were dominated by Daptonema tenuispiculum and Sabatieria punctata. For both species, the vertical distribution in the sediment seemed not dependent on the redoxchemistry, as former believed for S. punctata, but primarily influenced by food availability. This feature could also be recognized for Ixonema sordidum and Viscosia langrunensis, the most abundant nematodes at the coarse sandy station (790).

In general, nematode diversity was regulated primarily by sediment granulometry. Coarser sediments (station 790) yielded more diverse communities compared to the fine sediments (station 115, 702), however seasonal fluctuations and variations with depth into the sediment were not obvious. At the silty stations, when the sediment column was more oxidized in March, overall diversity was higher and showed a positive relationship to the mud content which varied with depth into the sediment. This positive relation is probably explained by an enhanced deposition of organic matter associated with the accumulation of fine particles near the river-mouths. Furthermore, the higher abundance, the lower diversity and the higher dominance found at the two silty stations of the eastern and the western part of the Belgian coast, pointed to a stressed, organically enriched environment.

The results demonstrate that controls on nematode community structure are complex and that information at both species and community level are required to properly evaluate the effects of natural and anthropogenic impacts.

The annelid community of a shallow Mediterranean lagoon (Gialova Lagoon, Ionian Sea) was studied on a seasonal basis. Out of the 39 species identified eight are reported for the first time from the central Mediterranean. The dominant species were the polychaetes Capitella capitata, Neodexiospira pseudocorrugata, Malacoceros fuliginosus, Perinereis cultrifera, Hediste diversicolor, Heteromastus filiformis and the oligochaete Limnodriloides maslinicensis. Uni- and multivariate methods were employed to study the community structure. The coenocline observed is strongly related to the degree of isolation; its main features (i.e. number of species, density, geometric abundance and size-classes) in space and time are presented and discussed in detail. The distribution pattern of the annelid community has been found to be governed by a different set of environmental factors in each season. Although this narrow lagoonal habitat suffers severe dystrophic episodes it manages to recover, demonstrating a seasonal community pattern.

Temporal patterns in metazoan parasite community diversity of Crassostrea gigas, (Lamellibranchia: Ostreidae) were studied in the Exe Estuary at monthly intervals over one year and in relation to host age-classes. A total of four metazoan species was found to parasitize C. gigas in the Exe Estuary: the turbellarian Paravortex sp., cercaria Lepocreadiidae, metacercariae of Renicola roscovita and the copepod Mytilicola intestinalis. Only R. roscovita and M. intestinalis were present in all months throughout the year and in all host age-classes. Analysis of the metazoan parasite community at individual host level revealed little variation in community structure with respect to season or host age, as only a slight increase in diversity values was observed during the summer months. However, community diversity does vary from year to year, as shown by comparison between host age group samples in three consecutive years. None of the parasites are specialist to oysters but all appear to be widespread and abundant parasite of other lamellibranch species.

The role of the ommastrephid squids Illex coindetii and Todaropsis eblanae (Mollusca: Cephalopoda) collected from two areas in the north-eastern Atlantic waters (north-west Spain) as hosts for larval ascaridoid nematodes was examined from November 1992 to November 1993. The morphology, morphometric growth, population dynamics and electrophoretic identification of the anisakid nematodes was described. The correspondence of Anisakis type I larvae recovered from both squid species within the sibling species Anisakis simplex B is confirmed by comparative data on morphology, morphometry, and genetic evidences. Almost all somatic structures showed progressive and continuous allometric growth corresponding with increase in worm length. Seasonal changes in parasite population levels were evident in both sampling areas.

Spectral reflectivity and transmission of the iridescent cuticle of six species of male Sapphirina (Poecilostomatoida: Copepoda) were measured by microspectrophotometry. Sapphirina angusta and S. opalina showed two spectral peaks of reflection, one at about 420 nm and the other at wavelengths longer than 750 nm. Sapphirina auronitens and S. gastrica had dominant peaks at wavelengths longer than 500 nm. Sapphirina ovatolanceolata had peaks between 430 and 600 nm, while S. metallina had various peaks along a wide range of wavelengths. The peaks at the longer wavelength in S. angusta and S. opalina may be related to the red pigments in the subcuticular layer of the species, or a result of a second-order effect of the multilayer system. The spectra of transmitted light were complementary to those of reflected light, indicating that the iridescence is caused by the interference of light by the integumental multilayer structure. The present results are also consistent with the hypothesis that the iridescence has a role in increasing the contrast of males against the ambient light conditions in the daytime distributional depth of the species.

Observations of female genital structures using light and scanning electron microscopy in 25 species of Acartiidae (Copepoda: Calanoida) show the presence of paired gonopores and egg-laying ducts with a typical semicircular configuration in all specimens. In the genus Acartiella, there is no seminal receptacle and the external genital area serves as storage site of the spermatophoral products forming an external mass. Unlike in the other acartiids, the genital structures present a complex organization with paired adjacent gonopores and copulatory pores. In almost all the species, the seminal receptacles exhibit characteristic loop-shaped seminal ducts which connect them to the egg-laying ducts. The functional morphology and taxonomic relevance of genital structures are discussed. The present results do not justify the Steuer's subgenus division of the genus Acartia, the very predominant one of the family.

Patterns of genetic and morphological variation among eight populations of Patella barbara along the coast of South Africa were examined to see whether reported differences in shell morphology and behaviour between the west and east coasts were mirrored by other morphological and/or genetic differences. Morphological analyses of radular structure, gut-loop coiling and sperm microstructure revealed no differences between the populations. Discriminant functions analysis based on shell morphometrics showed major overlap between populations and failed to separate them. Electrophoretic analysis of 17 enzyme loci gave an overall genetic identity (Nei) value of 0.995, a value which lies within the generally accepted range for conspecific populations. In two of the populations, at Dwesa and Arniston, individuals were found to be ‘gardening’ algal resources. At Clovelly, a ‘normal’ form of P. barbara was found on the rocks, whereas a reduced and tall-shelled form occurred on the ascidian Pyura stolonifera, demonstrating phenotypic morphological plasticity. It was concluded that different populations of Patella barbara are both morphologically indistinguishable and genetically homogenous along the coast of South Africa, thus providing good evidence for widespread gene flow.