Three exposed sandy beaches were selected to compare fluctuations in density of the most abundant species, and to verify the influence of spatial and temporal variations on the community structure. Sampling was carried out every three months, from June 1993 to May 1995, on Fora, Prainha, and Boqueirão Beaches. The first two beaches were classified by Dean's morphodynamic index (Ω) as intermediate, and the last as reflective. Slope, beach width and median grain size were significantly different among the beaches. Two-way analysis of variance revealed significant differences in species richness only among the beaches. No significant differences in density of the macrofauna between beaches and season were observed. However, Prainha Beach showed a higher temporal variation of the density of the macrofauna (and higher standard deviation) than the other two beaches. Emerita brasiliensis (Crustacea: Decapoda), Excirolana braziliensis (Crustacea: Isopoda), and Pseudorchestoidea brasiliensis (Crustacea: Amphipoda) were the most abundant species. Canonical correspondence analysis calculated the influence of the temporal variation as 27·5%; the influence of the environmental variation on community structure was 20·9%. The results suggest that in spite of the long-term fluctuations in species density, the beaches did not have temporal differences in the species richness and total density macrofauna during the study period.

The morphology and stomatogenesis of the marine scuticociliate Paranophrys magna, collected from a crab-culturing pond in Qingdao, China, were studied. It possessed typical characteristics of the genus Paranophrys. The stomatogenesis of this species corresponds basically with the results provided in previous studies for this genus, the main sequence develops can be generalized as follows according to the Qingdao population: (i) in the proter: the remnant of the parental paroral membrane generates the new paroral membrane and the scutica; and (ii) in the opisthe: both the paroral membrane and scutica originate from the proliferation of the anterior part of the secondary primordial field, membranelles 1&2 derive from the posterior part of the secondary primordial field, while membranelle 3 from the proliferation of the parental scutica which form the primary primordial field.  Some differences between our results and previous descriptions are compared and discussed.

Seasonal distribution of the ciliated protozoa was studied in the west part of Kaštela Bay during 1995. These are the first data of the annual distribution of four size categories of non-loricate ciliates and tintinnines in the coastal area of the central Adriatic Sea. The maximum densities of ciliated protozoa were recorded during the spring and autumn, when they could act as important factors of ‘top-down’ control. Contributions of non-loricate ciliates and tintinnines to the total of ciliated protozoa were 72 and 28%, respectively. The highest density of non-loricate ciliates was registered at the surface in September (1400 ind l−1). Annual variability of the non-loricates density was mostly influenced by changes in numbers of the second (103–104 μm3) and third (104–105 μm3) size categories and they constituted 86% of the total non-loricate counts. Non-loricates with biovolume <103 μm3 were the most abundant during the colder part of the year while those with biovolume >105 μm3 dominated during the summer. The highest density of tintinnines (718 ind l−1) was recorded at 5-m depth in May. Quantitatively, the most important tintinnin species was Helicostomella subulata. The results suggest a complex influence of biotic and abiotic factors on the annual distribution of ciliated protozoa.

Polychaete worms obtained by RRS ‘Discovery’ from 200 to 4850 m north-west of Africa in 1979 contained 24 species of which five: Macellicephala violacea, Bathyeliosona abyssicola, Laetmonice filicornis, Maldanella harai and Potamilla torelli were present in the abyssal zone (>2000 m). Macellicephala violacea is widely distributed in the Arctic and the present record is the southern-most record of this species. Fifteen species were recorded from the bathyal zone, many of which have a wide distribution in the oceans. A Neopolynoe species from the bathyal zone is new to science.

Several new symbiotic associations involving Syllidae (Annelida: Polychaeta) are reported. The number of known host sponge species infested by Haplosyllis spongicola is updated to 36, with seven hosts being reported for the first time (i.e. Aplysina corrugata, Aplysina sp., Cliona sp., Cliona viridis, Phorbas tenacior, one sponge from Iran, one sponge from Cambodia). Two infestation patterns (a few worms per host cm3 in temperate waters and 10s or 100s in tropical waters) are identified. The taxonomic and ecological characteristics of the species are discussed. Five associations occurring between four syllid worms and decapod crustaceans are fully reported for the first time. Syllis cf. armillaris, S.ferrani and S.pontxioi occurred inside gastropod shells occupied by hermit crabs as well as Pionosyllis magnifica, which was also found inside the branchial chambers of the giant crab Paralithodes camtschatica. The description of Pionosyllis magnifica is emended on the basis of the new specimens found, while some taxonomic remarks on Syllis cf. armillaris are given. In addition, further evidence of sexual (P.magnifica) and asexual (S. cf. armillaris) reproduction in symbiotic syllids is provided.

Differentiation between two samples of the polychaete Perinereis cultrifera collected in a brackish-water habitat and in an adjacent marine site at Elba Island (Italy) was assessed by morphological (number of paragnaths on the zones of the pharynx) and genetic (allozymes) approaches. Mean number of paragnaths differed significantly in zones IIl, IIr, III and V by t-test (P<0·05). Multidimensional scaling performed on Manhattan distances separated the individuals in two groups with a narrow zone of juxtaposition. Electrophoretic analyses of 22 allozyme loci revealed high levels of both within- and between-sample genetic heterogeneity, with a large number of private alleles. A general deficit of heterozygotes accounted for deviations from the Hardy–Weinberg equilibrium. Nei's genetic distance (D=0·185±0·018) and the mean value of the coancestry coefficient (Θ=0·381± 0·123, P<0·001 by permutation test) indicated considerable genetic divergence between the two samples. We concluded that the two groups can be assigned to sibling species. The observed divergence between the two samples may results from absence of gene flow and subsequent microallopatric differentiation through genetic drift, or, assuming migration between populations of the two sites, the model of divergence with gene flow may be compatible with this system.

A new species of Branchiomaldane was identified in a collection of polychaetes living in colonies of a stony coral. Branchiomaldane maryae sp. nov. differs from all other species of the genus by the presence of lensed eyes and 1–3 branchial filaments per parapodium. Comparisons between B. maryae sp. nov. and the other species of the genus are provided, together with some phylogenetic considerations on the position of the genus.

In order to find the most suitable parameter for measuring the nereidid Laonereis acuta, correlations between total length or weight and eight morphological measurements: width of prostomium and 2nd, 6th, 13th and 19th setigers, length of the prostomium, length through segment 6th and length through segment 13th, were established. The width measurements showed the highest values of r, and were the most reliable indicators of size. Comparisons between weight and morphological measurements showed a similar pattern as well as negative allometric growth.

Commensal and parasitic copepods (Arthropoda: Crustacea: Copepoda) of two common species of sea squirts, Phallusia mamillata and Ciona intestinalis have been investigated in the sea of Taranto (southern Italy).

A total of 2590 specimens of copepods were collected (five families, eight genera and 13 species). The sex ratio on 2582 specimens was 1228 males (47·56%) to 1354 females (52·44%).

The species were identified by the hosts in which they were found, their sex ratio host by host, and the specific variability and affinity analysis by means of the Sørensen index and the diversity index by means of the Shannon application.

Some species of copepods have been found for the first time as in Ciona intestinalis (Hermannella rostrata) and in Phallusia mamillata (Notodelphys canui, Doropygus pulex, Pachypygus gibber, Notopterophorus auritus, Lichomolgus albens, Hersiliodes latericia). The association Notodelphys canui–Doropygus pulex—Notopterophorus auritu–Lichomolgus albens is noted for the first time in the Mediterranean Sea.

The reproductive biology, in response to temperature, season and copper, of a coastal population of opossum shrimps (Crustacea: Mysidacea) was measured. The reproductive pattern for Praunus flexuosus at Keyhaven (west Solent, southern England) has maximum activity in April and maximum reproductive effort in May/June. Increasing temperature decreases incubation time and the reproductive pattern is adapted to compensate for temperature effects. Reproduction was inhibited with copper exposure. Fertilization of the eggs did not occur in any copper treatment (5, 25, 75, 200 μg l−1 copper added). Brooding females exposed to copper suffered a high abortion rate. The inability to produce broods, appears to be a long-term effect, as specimens previously exposed to copper did not produce any broods after two weeks in seawater controls.

The trophic behaviour, stomach contents, and morphology of the feeding appendages, with emphasis on setae, of a species of Laomediidae, Axianassa australis (Crustacea: Decapoda: Thalassinidea), were investigated. This species is a deposit feeder. The 32 described setal types were clustered in four main categories: plumed, serrate, plumodenticulate and simple. By examining the setae and spatial position of the segments of the appendages, it is possible to infer that the main function of the 1st and 2nd pereiopods, the 3rd pair of maxillipeds, as well as the dactylus, propodus, carpus and merus of the 2nd maxilliped, is to brush particles. The ischium, basis and coxa of the 2nd maxilliped appear to be specialized for particle retention. For the remaining mouthparts, brushing is generally the main function of the basal endites, while the coxal endites retain particles. Patterns of morphological adaptations to feeding habits are proposed for the Thalassinidea based on a review of the literature. Setal diversity, ratio of plumodenticulate to serrate setal types and mandible morphology are linked to ecological adaptations to trophic modes. Conversely, the presence and degree of development of the crista dentata appear to be related to phylogenetic heritage rather than to feeding mechanisms. Stomach contents are also indicative of trophic modes used by the species; while the predominance of small particles can indicate either filter or deposit feeding, stomach contents with high quantities of large particles suggest deposit feeding as the exclusive trophic mechanism.

Epixanthus dentatus (Crustacea: Brachyura: Eriphiidae) is a predator crab, commonly inhabiting East African mangroves, whose nocturnal and elusive behaviour usually prevents analysis of its natural diet and prey selection. The present study was carried out on a population inhabiting a peculiar mangrove habitat in which E. dentatus produces heaps of non-ingested parts of its prey. Fifty-nine of these accumulations of prey remains were examined and 17 species were identified as part of the diet of E. dentatus. Relative prey consumption was then analysed with respect to the relative abundance of prey species within the local faunal community. This methodology provided important information about prey selection by E. dentatus; in particular, gastropods were always strongly under-represented, while there was an active selection among the different crab species. Uca species were under-represented, while swimming crabs were also part of the E. dentatus diet, which shows that the latter is able to prey both at low and high tide.

The distribution, abundance and recruitment of Chthamalus species were studied for one year at two rocky shores on the central coast of Portugal. Chthamalus montagui is the most abundant intertidal barnacle on the Portuguese mainland. Higher abundance of C. montagui was found on the lower levels of the more sheltered shore, which is closer to the influence of the Tagus estuary. Chthamalus stellatus was also present, in very low densities, and always confined to the lower level of the barnacle zone. Chthamalus stellatus was more common at the shore farther away from the estuary, in which exposure to wave action is higher. The metamorphs of C. stellatus settled at the studied shores are considered to be immigrants from other populations, where the density of adults is sufficient for cross-fertilization to occur. Chthamalus spp. recruited almost continuously throughout the year, with a peak between July and September and a gap during February and March. Variations in phytoplanktonic assemblages and temperature may be the main factors controlling the reproductive season of Chthamalus spp. Recruitment was usually stronger on the lower shore levels but extended for a longer period higher on the shore. Seasonalvariations of C. montagui abundance were greater on the lower levels of the more exposed shore. This is probably due to faster growth and higher mortality of barnacle populations occupying the lower shore levels at the more exposed habitats.

European lobsters (Homarus gammarus) were sampled from nine sites around the UK coast to determine whether populations could be differentiated on the basis of morphometric variability, and to relate this to depth and indices of population size at each site. Discriminant analysis indicated that exoskeleton damage was the only characteristic that could distinguish males between sites. In contrast, females were distinguished between sites on the basis of variation in exoskeleton damage, claw spines and rostrum teeth, which tended to be positively correlated to indices of population density. This study suggests that female morphology may respond more strongly than male morphology to local selection pressures, albeit in a limited capacity.

The crustacean species composition in the intertidal zones of 13 sheltered unconsolidated marine beaches in south-eastern Brazil is described. Fifty-three crustacean species were collected, adding 46 species to the total reported by previous studies in the same region. Decapods dominated the community, in contrast to exposed sandy beaches where peracarids normally predominate. The species were distributed irregularly among the beaches. Richness varied markedly among sites, and was positively related to a combination of factors such as fine sand grains, high organic matter content, and relatively low silt–clay content. The presence of rock fragments enabled both rocky shore and sandy beach crustaceans to occur on the same beaches. Richness and abundance of crustaceans showed no clear relationship to sediment grain size and slope, in contrast to the norm for exposed sandy beaches. The dominance of the tanaid Kalliapseudes schubarti in some areas may be a result of organic matter pollution in the region. These beaches showed higher species richness than typical sheltered and exposed sandy beaches, indicating that this sheltered, highly heterogeneous seascape is an important area for conservation.

An automated photographic technique was used to collect quantitative information on the activity patterns of Fissurella crassa under heavy-exposed sea conditions.The activity of this key-hole limpet was confined to nocturnal low tides. Total length of excursions was significantly greater during spring tides than neap tides, as was the maximum distance reached from the refuge. Total duration of excursions and their average speed did not vary significantly according to the spring/neap cycle. While the direction angle of excursions relative to the refuge was not influenced significantly by the spring/neap cycle, the lowest zone within the intertidal was reached by F. crassa during spring low tides only.

Fissurella crassa showed a spatial activity pattern fluctuating intra/inter-individually between a central place foraging and a ranging strategy, with a marked propensity for the former. Looped excursions were characterized by higher speed for the movements away and toward the limpet's refuge, than the movements at maximum distance from the refuge. As the outward and inward branches of looped excursions often overlapped extensively, trail-following is suggested as the main mechanism of orientation used by F. crassa to relocate the refuge.

Egestion in the intertidal mud snail Hydrobia ulvae was investigated under conditions in which coprophagy did not occur, both in laboratory populations (comprising 11 experimental densities from 1000 to 120,000 ind m−2) and in a field population with an average density of 50,000 ind m−2 (24 test densities spanning the local range of <5000–>120,000 ind m−2). In contrast to an earlier study that suggested marked reduction in egestion rate in H. ventrosa as a consequence of interference competition, no such effect occurred in the natural population of H. ulvae, or in the experimental populations except at densities of at least 100,000 ind m−2. Neither did any significant increase in inactivity or movement off the experimental substrata occur with increasing density. These results are discussed in relation to resource limitation in natural densities of mud snails.

The biological characteristics of Elysia subornata (Mollusca: Opisthobranchia) were studied in an aquarium to assess its risks and chance of success as a potential biological control agent against the invasive alga Caulerpa taxifolia (Chlorophyta) in the Mediterranean Sea. This species feeds only on Caulerpa and has benthic larval development. Dietary switching is possible on some Mediterranean Caulerpales but feeding on other algae and sea grass is unlikely. The main limiting factor for the success of studied Caribbean strain of E. subornata are the Mediterranean winter temperatures which are lethal for that species. For the five months of the year which are favourable for feeding, growth and reproduction, the tested strain of E. subornata cannot reach a population density capable of controlling C. taxifolia.

Since the degree of syphonal opening can be an index of the pumping activity, the shape and the surface of syphon openings in Mya arenaria were filmed with an underwater camera at two stations in the middle of the intertidal zone. The individuals were perpendicularly oriented to the main current direction or parallel with the inhalant syphon upstream during flood tide, causing refiltration risks during ebb tide. The surface of the inhalant opening (SI) was strongly reduced with increasing current speeds. Its shape (XI) varied with the individual's orientation and had a tendency to become more circular with time. The surface of the exhalant opening (SE) decreased and its shape (XE) flattened with increasing current velocity and with time. However, variations of XI and XE were weak. Current direction had no significant effect on SI, SE, and XE, but did cause a strong decrease of the SE/SI ratio during ebb in individuals exposed to important refiltration risks during ebb tide. Significant negative correlations between stomach content in phaeopigments and SI and SE suggest that a syphonal constriction could contribute to more efficient feeding. For parallel oriented individuals, the decreases of SE, SE/SI, and XE during ebb can then be interpreted as an attempt to deviate or increase the excurrent velocity relative to the incurrent so as to limit refiltration. We suggest that decreases in opening surface and shape may serve, above all, to increase syphon current jet velocity in syphonate bivalves.

The morphology of the cells during spermatogenesis in Amiantis umbonella (Mollusca: Bivalvia) was investigated from collections made between November 1997 and January 1999. Each stage is described and prominent features noted. The mature spermatozoan is primitive, lacking an apical rod, having a cylindrical-curved nucleus and a cone-like acrosomal complex bearing distally two swollen bulb-like terminals connected by thin, curved threads. Spermatozoa have a single flagellum and five (rarely six) mitochondria at the base of the nucleus.