One hundred and three suprabenthic hauls in the Seine Estuary were taken on a marine to fresh water gradient with a modified Macer-GIROQ sledge during 1996 to collect Benthic Boundary Layer fauna. Two main species assemblages were identified along the salinity gradient: (1) a marine assemblage located in the downstream part of the estuary dominated by amphipods and mysids such as Schistomysis spp. and Gastrosaccus spp.; (2) an estuarine assemblage essentially dominated by the mysid Neomysis integer, recorded along the salinity gradient with maximal abundance observed between 15–10 psu. The decapod Palaemon longirostris and the goby Pomatoschistus microps were located in the upstream part of the estuary where they presented maximal abundances. Some species used the estuary during juvenile development such as the mysid Mesopodopsis slabberi (Van Beneden, 1861) and decapod Crangon crangon. Although the morphological characteristics of the Seine Estuary (weak estuarine area and important dredging) are different than other major European estuaries such as Gironde, Westerschelde and Ems, the longitudinal distribution of the demersal community presented similar patterns in all sites. Nevertheless, monthly sampling permitted to determine the seasonal location and abundance changes of the demersal assemblages in the Seine estuary. Marine assemblages presented maximal densities during summer and autumn while estuarine species were most abundant during spring and summer. Longitudinal changes of main demersal species during an annual cycle showed an increase of spatial distribution along the salinity gradient for marine and neritic species during spring and summer with a penetration of species in the estuary. The abundances of both assemblages were very high (annual mean >5000 ind 100 m−3) whereas the biomass of the estuarine assemblage was very important (annual mean ≅38 g ash-free dry weight 100 m−3).

A study was conducted between 1997 and 1999 to investigate meiofauna assemblages from selected inshore and offshore locations around the UK coast. The main objective was to relate the differences in meiofauna distribution patterns to a number of measured environmental variables and to establish more clearly the sensitivity of meiofauna communities to anthropogenic disturbance. Results from univariate and multivariate data analyses show that distinct spatial differences in species distribution patterns exist and that these correlate with the natural physical characteristics and concentrations of trace metals in the sediment. Abundance and diversity of meiofauna assemblages were generally higher offshore than inshore and this difference can be attributed to both natural processes and anthropogenic impacts. The inclusion of meiofauna in applied monitoring programmes offers the potential for improving the resolution of the spatial extent of anthropogenic impacts over that achievable from macrofauna investigations alone.

Continental shelf and upper slope fish communities were studied along the Catalan coast based on 66 experimental bottom otter trawls. A total of 79 demersal fish species were studied by means of cluster analysis and multi-dimensional scaling (MDS) ordination for community structure. Analysis revealed the existence of five major location clusters. Similarity percentage analysis (SIMPER) was determined by comparing the dissimilarity between two groups of samples using the discriminating species. Geomorphological characteristics, bottom substratum and depth showed direct influences on species assemblages. High correlation between the biotic data samples and depth was observed. The fish species assemblages identified five main demersal fish associations which corresponded with the five location clusters and with five benthic sediments (mud of the upper slope, sand and gravel, mud of the shelf, muddy-sand and sand with rocky outcrops).

Morphometric characteristics and spatial distribution of Tontonia grandis sp. nov. were investigated in the northern East China Sea and the adjacent sea areas. Tontonia grandis has a large conical body shape, 113 μm (70–155 μm) in length by 55 μm (40–113 μm) in width, a caudal appendix, multiple macronuclei and 14 (13–16) anterior and 28 (24–33) ventral polykinetids. Some cells have numerous cortical platelets on the surface and others do not. These two forms showed different horizontal distribution, and hence the presence of cortical platelets might be influenced by the environment inhabited. However, various forms of caudal appendix were observed, which constitute a continuous series of their developmental stages. This result might suggest that the caudal appendix is replaced by new growth and repeats its developing and sloughing spontaneously.

Ptychodactiaria, currently recognized as an order equivalent to Actiniaria (sea anemones sensu stricto) and Scleractinia (‘true’ or hard corals) of cnidarian class Anthozoa, contains three monotypic genera, Dactylanthus, Ptychodactis, and Preactis, in two families, Ptychodactiidae and Preactiidae. Features that had been considered distinctive to the order among hexacorallian anthozoans were that gametes mature in protrusions from the mesenteries, as in octocorallian anthozoans, and that gametes do not mature embedded in mesogloea. However, we found that ptychodactiarian gametes develop in the mesenteries, surrounded by mesogloea, as in other sea anemones. We conclude that the three species constitute a clade, the most distinctive feature of which is medially fused mesenteries at the proximal end of the body. This clade merits subordinal status within order Actiniaria. We redefine Ptychodactiaria and its component taxa, moving Dactylanthus from family Ptychodactiidae to family Preactiidae.

Monthly collections were made for one year (August 1995 to July 1996) in the intertidal zone of two beaches (Engenho d'Água and São Francisco) located in the São Sebastião Channel, State of São Paulo, Brazil, in order to establish the seasonal fluctuations of the species and the factors determining these fluctuations. On each beach, a 10 m wide sector of varying width was established, from which 15 samples/month were collected with a cylindrical corer (0·01 m2). The salinity of the interstitial water and the temperature of the sediment were measured monthly, while the granulometric parameters and calcium carbonate and organic matter concentrations were recorded seasonally. The temporal distribution of the species was more homogeneous at Engenho d'Água, where the highest diversity and evenness values were also found, although the number of individuals was lower. At São Francisco, the monthly abundance was higher, but the richness, diversity, and evenness values were lower, showing some heterogeneity in the temporal distribution patterns of the species. Most species at Engenho d'Água reached their peak of abundance in summer and autumn. The most abundant and frequent species at Engenho d'Água were Nematonereis hebes, Cirriformia filigera (summer), Scyphoproctus djiboutiensis (spring), Owenia fusiformis and Isolda pulchella (winter). At São Francisco, the capitellids Capitella capitata, Heteromastus filiformis, and Capitomastus minimus, and the tubificid oligochaetes dominated in the summer, and Laeonereis acuta and Scolelepis squamata in the winter. The log-normal distribution of the species was used to group those species that are sensitive to and those that are tolerant of organic enrichment, over the four seasons of the year.

A study of the polychaetes living on isolated seamounts was undertaken to give data on marine biogeography and the dispersal of marine invertebrates. The data from the Meteor and Josephine seamounts came from Hartmann-Schröder and Rosenfeldt's work in the 1980s. Data from Hyeres came from Bellan's work in the 1960s, and data from the Atlantis and Hyeres seamounts were obtained during the Seamount 2 French expedition on board the ‘Suroît’ in 1993. Thirty-five sites from 280 to 2205 m were sampled: 16 on Atlantis (13 with polychaetes), and 19 on Hyeres (16 with polychaetes). In all 84 polychaete taxa from four seamounts were studied: Atlantis, 36; Hyeres, 33; Josephine, 34; and Meteor 50, but data analysis was based on the following number of taxa: Atlantis, 31; Hyeres, 29; Josephine, 34, and Meteor 48. Two groups of sites were identified by cluster analysis: I, Atlantis and Hyeres; and II, Josephine and Meteor. Only seven species were present at all sites. Nine families were present only in group I and six other families only in group II. Hesionidae (three species) occurred in group I, conversely Syllidae (16 species) were sampled only in group II. Some of the species were cosmopolitan (31%), 49% had a large distribution in the Atlantic, 11% were lusitano–mauretanian species, and only 6% were endemic; 51% of the species have direct development against 46% of the species which had a planktotrophic development and 3% a lecithotrophic development. Results of the biogeographical distribution and reproductive patterns of the polychaetes collected on these four sites were compared.

Several specimens of monstrilloid copepods were collected in different localities of Brazil between 1993 and 1997. The taxonomic analysis of these specimens yielded the identification of two new species of Monstrilla. The first one, M. careli sp. nov. can be distinguished by a combination of several characters, including its body proportions, with a very long cephalothorax, by the particularly long terminal segment of the antennules, by the structure of its fifth legs, and by the very long dorsal seta on the caudal rami. The second species, M. brasiliensis sp. nov. can be distinguished by the peculiar features of its fifth leg, with a patch of long and stout hair-like setae along its outer margin; it has also a notched protuberance near the antennule bases. It has a notch on the anterior protuberance of the genital somite, and a ventrally swollen cephalothorax. This species, together with M. inserta Scott bears a pair of enigmatic structures which are either modified sensillae or a vestigial postantennular appendage not previously described in the Monstrilloida.

This paper presents the first record of Ceratothoa steindachneri from Cornwall, making it the first resident species of the fish–parasitic isopod family Cymothoidae in Britain. The host is Echiichthys vipera (Trachinidae) the lesser weever fish, the isopod attaching to the host tongue. A complete redescription and reillustration for C. steindachneri is given, and a neotype is selected for the species Ceratothoa parallela. A key to the north-east Atlantic and Mediterranean species of Ceratothoa is included, with a brief illustrated account for each species.

The present study evaluated shell utilization and preference of two sympatric hermit crab species, Calcinus tibicen and Clibanarius antillensis, from Ilha Galheta de Dentro, Vitória Bay, south-eastern Brazil. Distribution of individuals and use and availability of shells were estimated in the field, where micro-habitat and shell partitioning were demonstrated between the two species of crabs. Calcinus occurred in higher numbers in the infralittoral fringe and shallow subtidal, while Clibanarius was found mainly in the midlittoral zone. The crabs used shells of different architectures and sizes. Calcinus used mainly globose and low spired shells (Tegula viridula and Cymatium parthenopeum), while Clibanarius utilized predominantly the elongated and high spired ones (mainly Cerithium atratum). Clibanarius used shells with smaller volume, weight, and aperture. Free access experiments were conducted in the laboratory and showed that Calcinus and Clibanarius had a high satisfaction rate, i.e. only 50% of the crabs exchanged their shells. From those that exchanged, they chose shells with higher internal volume than that used in the field, while shell weight did not present any increase. Clibanarius was found in shells closer to the preferred ones and in a very different proportion from shell availability, contrasting to Calcinus, which followed shell availability instead of their preferences. Shell internal volume was more important as a choice factor than the weight for both hermit crab species, showing that crabs optimized shell volume in relation to shell weight in the free access experiments.

Hermit crab populations have been described in different habitats and latitudes but few studies focused on coexisting populations. Such information is especially important to evaluate the effect of coexistence in the population biology of such organisms. This study was done in the intertidal region of Pernambuco Islet, São Sebastião Channel, south-eastern Brazil. Random samples of crabs were taken monthly during one year to evaluate their size and sex. The three coexisting Clibanarius populations (C. antillensis, C. sclopetarius, and C. vittatus) showed similar patterns of sex ratio (skewed for females), sexual dimorphism (males larger than females), recruitment (February to June) and population growth but differed in size structure (Cs>Cv>Ca) and reproductive activity over the year. Population growth was estimated using the von Bertalanffy growth function (VBGF) and revealed that the growth of these three populations was strongly reduced from August to January and that longevity varied from 42 to 48 months. Clibanarius antillensis showed continuous reproduction with high frequency of ovigerous females over the year while C. sclopetarius and C. vittatus had a reproductive peak in April and absence of ovigerous females in August/September. Coexistence seemed to influence population biology of these hermit crabs, given the relationship of their reproductive periods and growth patterns to the shell adequacy to the crabs. The overlap in reproductive peaks and recruitment periods may strengthen competition for shells. Comparisons of the reproductive patterns of the hermit crab populations recorded to date emphasize that reproduction and, consequently, life strategies of hermit crabs are not directly dependent on taxonomic or geographical proximity, but on their evolutionary histories and on local processes acting on each assemblage or population.

The first results of the females reproductive cycle of Maja brachydactyla (Braquiura: Majidae) off the coast of Asturias (north-west Spain) are presented. Mean size of mature females was 133·4 mm (N=1022) in 1997 and 125·0 mm (N=942) in 1998. Only one cohort is exploited each fishing season. This cohort passed through the terminal moult the year before and recruited in to the fishery beginning in June. The breeding cycle off the coast of Asturias begins in December and ends in November the following year. Results from this study indicate that females produce 3–4 broods per year in these waters, which is the highest reported number for M. brachydactyla. The results are discussed in terms of their importance for management of the fishery.

During three consecutive years of observation 23 Atlantic cod (Gadus morhua) were tagged with ultrasonic transmitters as part of two experiments to determine the movement patterns of adult cod in the genetically distinctive population inhabiting Gilbert Bay, Labrador. Individual cod were relocated for periods up to 15 months, indicating year-round residency within the bay despite unimpeded access to the open ocean. The tracking data show that individual cod have a strong homing tendency. In experiment 1 displaced cod returned (homed) to their place of capture in a small arm separated from the rest of the bay by a shallow sill while non-displaced fish remained at their capture site. In experiment 2 some cod remained within 2 km of their capture/release site, a spawning area, while others ranged widely in Gilbert Bay before returning to this site. Whether an individual ranged widely or had more restricted movements was not related to size. Cod exhibited wider ranging movements in the spring and early summer, following spawning, than in the late summer and early autumn. The return of Gilbert Bay cod to specific locations in the inner part of the bay to overwinter and spawn is evidence of one mechanism that could have led to their genetic distinctiveness.

The stenophagous ascoglossan (=sacoglossan) opisthobranch Elysia viridis has long been a model organism for the study of endosymbiosis or kleptoplasty as well as one of the few herbivores to consume the introduced green macroalga Codium fragile on European shores. Larval and post-larval dynamics of the ascoglossan were investigated. Planktotrophic larvae of E. viridis grew at 5–10 μm d−1 (shell length) at 15°C on a unicellular algal diet (the cryptophyte Rhodomonas baltica); larvae became competent one month post-hatching. Effective feeding and chloroplast acquisition typically started within 2–3 d of metamorphosis. Slugs grew about 8 mm in the first month of post-larval life. During this period, juveniles held in the light did not grow faster or survive better than conspecifics held in the dark; thus, functional kleptoplasty did not occur during first three weeks of benthic life. While larval growth rates and the nature of metamorphic cues are consistent with those of many other opisthobranch species with planktotrophic larvae, measures of post-larval growth—particularly as it pertains to kleptoplasty—is a new contribution to opisthobranch biology.

Giemsa-stained blood smears were examined from 70 deep demersal fish of 27 species in 20 genera, trawled from depths of 747–4143 m in the region of the Porcupine Seabight, north-east Atlantic. Infections were found in four species of teleosts in three families: 1/3 Alepocephalus rostratus and 1/3 Narcetes stomias (Alepocephalidae); 2/3 Antimora rostrata (Moridae); and 1/1 Cataetyx laticeps (Bythitidae). Blood films from C. laticeps and Antimora rostrata were well preserved but those from the other two species were less satisfactory. The blood parasites included two types of haemogregarines, Haemohormidium-like and viral erythrocytic necrosis (VEN)-like infections. Haemogregarina (sensu lato) johnstoni sp. nov. was described from C. laticeps captured at 1541 m. This haemogregarine was unusual in apparently having dimorphic gamonts, some with prominent caps. A second, but monomorphic, haemogregarine found in Alepocephalus rostratus captured from 985 m, was named as Desseria sp. since only extracellular stages were observed. Haemohormidium-like organisms were found in Antimora rostrata taken from 2441 m, and were similar to those described previously from this deep-sea fish. A VEN-like infection from one N. stomias captured from 2567 m was reported. No marked effects on host cells were evident in any of these blood infections.

Development of the olfactory system in anemonefish embryos of the species Amphiprion melanopus was examined from day six post-fertilization, until hatching (day nine). An olfactory placode with receptor cells lining the epithelium and nerve axons from the placode into the olfactory bulb, was observed on newly hatched embryos. In addition, two different secondary bilateral receptor systems were found. These findings may firstly support the anemonefish host imprinting hypothesis, and secondly indicate that the ontogenetic timing of this imprinting mechanism occurs towards the end of the embryonic development.

Density and size of Chromis fumea (Pisces: Pomacentridae) were regularly monitored during 13 months (from August 1996 to August 1997), on two artificial reefs in New Caledonia (south-west Pacific ocean): a ship-wreck (CT2) just after scuttling, and an assemblage of iron boxes (Caissons) sunk more than 50 years ago. The settlement of C. fumea was first observed 20 August 1996 and lasted 20 days. At the beginning the recruits were 1 cm size-class fish and at the end 2 cm size-class. This major settlement phase was again observed one year later (September 1997). A second minor settlement phase occurred in December 1996 on CT2. Significant immigration of adults was also observed between November 1996 (6 cm) and April 1997 (7 cm), indicating that this species is capable of medium range migration (>50 m). Population size decreased by 87·8% between the settlement of juveniles and the first immigration phase of adults. The final density of the 1996 cohort was 10·5% of the initial input of recruits on CT2 and 19·3% on Caissons. Initial density of recruits was 3·4 times higher on CT2 than on Caissons, whereas density of juveniles was similar at the end of the survey, indicating that post-settlement mortality was greater on CT2. Chromis fumea von Bertalanffy growth models were similar on CT2 and Caissons. This short-lived species is characterized by an initial rapid growth phase (K>3·36 y−1), with the fish reaching 68·5% of L∞ in three months, and a second slower growth phase (1 cm in ten months).

Cold vapour atomic absorption spectrophotometry (CV-AAS) was used to evaluate total mercury concentrations in Posidonia oceanica, after initial mineralization of the samples in a microwave oven. Measurements were taken of three leaf tissue types: the adult leaf blade, the adult leaf sheath, and the intermediate leaf blade. Plants were sampled monthly over a one year period at two sites presenting different degrees of pollution: Rosignano (Tuscany, Italy) and Tonnara (Corsica, France).

The mercury concentrations recorded in the different P. oceanica tissues were systematically higher at the more contaminated of the two sites, thus confirming the value of this plant as a biological indicator. The mercury concentrations observed exhibit seasonal variations, with higher concentrations recorded in winter than in summer. These variations seemed to be negatively correlated to the plant's phenology. Also, the mean mercury concentrations were generally lower in young tissue (intermediate leaf blade) than in the older tissue (adult leaf blade).

The variability in density estimates of intertidal, infaunal benthos due to the shape and tidal orientation of sampling devices is discussed. Although all intertidal sampling devices are fundamentally of the same design, three different cross-sections were investigated, square, circular and rectangular, with the first two of common use in intertidal sampling. Results demonstrated that tidal orientation of the sampling device does not induce variability in density estimates. Furthermore, no difference in density estimate could be detected between the square and circular cores, both having a very similar cross-section. In contrast, some species exhibited significant differences when comparing rectangular vs square/circular cores combined. It is postulated that these are caused by species-specific small-scale spatial patterns.

A preliminary comparative analysis of colony growth and zooid size in the perennial bryozoan Flustra foliacea (Bryozoa: Cheilostomatida) reveals reduced colony growth in the Bay of Fundy relative to growth in the Menai Straits and the Skagerrak, while seasonal fluctuations in zooid size are in synchrony with temperature regimes. Such retrospective morphometric analyses may allow inferences of primary productivity and thermal regimes and provide insights into the life histories of both Recent and fossil bryozoans.