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.

Oval squid Sepioteuthis lessoniana hatchlings originated from maternally identical egg strings were incubated under constant temperature and examined with special reference to statolith formation. Statoliths of a hatchling already had an adult-like shape, and some increments were observed. In spite of the maternally identical origin and constant incubation temperature (25°C), dorsal mantle length and statolith length of the hatchlings varied from 4.70 to 6.26 mm and 320 to 410 μm, respectively (N=14). These variations had a positive correlation with the embryonic duration ranging from 22 to 27 d, which means that the size of body and statolith becomes larger in hatchlings hatching later.

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 bryozoan Cigclisula sp., is a heavily calcified erect species which occurs abundantly in the shallow sublittoral coral reef at Quilaluia Island, Quirimba Archipelago, northern Mozambique. It grows in an arborescent bilaminate form termed adeoniform on the undersides of coral heads or other available bioconstructed hard substratum. The geography and bathymetry of the area results in periodic high and complex current regimes often carrying water borne debris. If this periodic force overcomes the structural integrity of Cigclisula sp. either the outermost branches break or the colony topples at the base. The local population was dominated by young individuals: nearly 40% of the sample population had ten branches or fewer and less than 10% had more than 50 branches (these could be ascertained as young due to the lower proportion of damaged colonies with ≤10 branches; Figure 1). The only size group with no damaged specimens (branch breakage) were those with ≤5 branches. The mean proportion of branches broken significantly increased with increasing colony size. After one year a population of Cigclisula sp., initially comprising 30 colonies (encompassing the entire size spectrum of colonies), consisted of just one small specimen.

Callista chione is the most prominent suspension-feeding bivalve species inhabiting the soft bottoms of the Bay of Banyuls-sur-Mer. Ingestion rates and absorption efficiencies when fed monospecific cultures of either phytoplankton (Pavlova lutheri) or bacteria (one natural strain isolated from the marine environment) were determined using 14C radioactive pulse–chase feeding experiments. Microalgae were ingested at a rate five to six times higher than bacteria (i.e. 2.31×10−3 against 0.40×10−3 mg DW mg SFDW−1 h−1). Such differences were attributed to differences in average particle sizes. Bacteria were also less absorbed than microalgae (i.e. 64.3 vs 83.8%). Together with existing data regarding the ratio of free to attached bacteria in the oceanographic environment, these results suggest that free bacteria probably contribute to meet only a small portion of the energy requirements of adult C. chione populations.

The deep sea protobranch bivalve species Ledella pustulosa recently has been described as comprised of four subspecies, differentiated on subtle and qualitative differences in shell morphology. Two of these, L. p. pustulosa and L. p. marshalli, possess overlapping geographic distributions, L. p. pustulosa occurring on the continental slope, and L. p. marshalli occurring on the continental rise and at upper abyssal depths. Principal components analysis was applied to six samples of Ledella pustulosa from the Rockall Trough in order to explore patterns of variation in shell shape and to test whether the variability follows a depth-related cline which might be under environmental control. Two of these samples had previously been identified as L. p. pustulosa and L. p. marshalli, respectively. The distributions of shapes at every depth overlapped broadly with the distributions from other depths and none of the depths had uniformly distinct shells. However, the mean shapes of the six samples divided into two clusters: a shallow cluster characterized by a lower dorsal profile (smaller ‘shoulders’) and a deep cluster with larger ‘shoulders’. No bathymetric cline in shape was found within these clusters. A discriminant function based on training samples of L. p. pustulosa and L. p. marshalli correctly identified 84% of the shells in the training samples and was applicable over a wide range in shell size. It showed that the subspecies differed primarily in the dorsal profile. The discriminant function was applied to 598 shells from depths of 1632–2900 m in the Rockall Trough in order to test the hypothesis of depth-related segregation of the subspecies. Although individual variability was high, the results indicated a gradual transition from L. p. pustulosa dominance at ∼2000 m to L. p. marshalli dominance at 3000 m depth, but not marked segregation. A sample from 1632 m depth with large proportions of both subspecies disrupted the bathymetric trend and suggested a latitudinal gradient in distribution. Possible environmental factors, including bottom currents, acting on a common genotype to cause the observed pattern of differentiation, are also discussed.

During 1996–1997 a systematic sampling programme was carried out in brackish coastal lakes and lagoons and in the delta of the River Po. In six of the nine collecting locations, 12 species of Gastrotricha were identified. One species, Chaetonotus ichthydioides, is new to science; another three species, the chaetonotidans Heterolepidoderma foliatum and the macrodasyidans Dendrodasys ponticus and Turbanella cf. pontica, and one macrodasyidan genus, Paradasys (P. subterraneus), were found in Italy for the first time. The unusual morphology of some of the species identified shows that Gastrotricha colonized brackish waters from both marine and freshwater habitats.

Eight samples of Littorina tenebrosa and L. saxatilis (Mollusca: Gastropoda) from Ireland and Britain, including pairs of each form from two locations in Ireland, were screened for genetic variation at 12 polymorphic enzyme loci using starch gel electrophoresis. Levels of polymorphism and heterozygosity were similar in L. tenebrosa and L. saxatilis, apart from a sample of L. tenebrosa from Britain which was less polymorphic than the Irish samples. No alleles were found to be unique to either form. Phylogenetic analysis using UPGMA showed that L. saxatilis and L. tenebrosa populations clustered as a monophyletic group. Nevertheless, the mean genetic distance between parapatric populations of L. saxatilis and L. tenebrosa (D=0.076) was similar to the mean for allopatric populations of either species (D=0.080). This indicates that there is a barrier to gene flow between the two forms Despite this, L. tenebrosa does not merit specific status since populations of this snail do not cluster as a distinct group, separate from L. saxatilis populations.

The spatial patterns of butterflyfish assemblages (Chaetodontidae) were examined within and between five islands of the Ryukyu Archipelago, southern Japan. Despite being the northernmost reef communities in the world and despite the severe natural and human-induced disturbances that have affected them since the 1970s, the coral reefs of the Ryukyu Islands have one of the most diversified assemblages of chaetodontids in the world. A total of 30 species were identified, and species richness per island ranged from 20 to 25 species. On each of the 45 stations prospected, between four and 17 species were recorded, and between 0.75 and 21.75 ind 250 m−2 were counted. Variation in species composition, species richness and abundance between islands was less pronounced than the variation within islands, where assemblages of the major reef environments (i.e. the reef flat, the reef edge, and the reef slope) were distinguished. The highest species richness and abundance were found on the reef slope and the reef edge. Canonical correspondence analysis revealed that depth, substrate complexity, and live coral cover influenced the distribution of chaetodontid fishes. These factors accounted for 20% of the variation in the species data matrix.

Age and growth of Loligo vulgaris and L. forbesi were studied by the examination of growth increments in 96 and 135 selected (white zone <10%) statoliths, respectively. Squid were obtained by monthly sampling from the catches of commercial trawling and hand-jigs in Galician waters (north-west Spain) between February 1991 and October 1993. Mantle length (ML) of L. vulgaris ranged from 70 to 480 mm and varied between 70 and 685 mm in L. forbesi. A negative allometry between statolith length and ML or body weight (BW) was found in both species. Sexual dimorphism was apparent in both species, males grew faster and longer than females. The statolith analysis suggests that growth patterns of L. vulgaris and L. forbesi in Galician waters are different. The exploited population of L. vulgaris was composed of two groups: one formed by individuals hatched in winter–spring and another by specimens hatched in summer–autumn. Squid hatched in winter–spring reached larger sizes at the same age than those hatched in summer–autumn. These two groups were also observed in L. forbesi. However, squid of this species hatched in winter–spring were smaller than those hatched in summer–autumn at the same age. Reasons for this discrepancy are discussed. The life span of L. vulgaris was about one year whereas the life span of L. forbesi extended to 18 months.

The Pacific oyster Crassostrea gigas (Mollusca: Bivalvia) was introduced to Ireland in 1965 and is farmed at many sites around the coast. The reproductive biology of 1377 oysters from two sites on the south coast of Ireland was examined from April 1996 until December 1997 for variations in maturation rate and condition indices. Qualitative data were compiled by staging gonadal development using histological sections. Environmental parameters of temperature, dissolved oxygen and chlorophyll-a levels, as well as parasites and pathology were monitored. Unusually high sea temperatures led to oysters in Dungarvan (site 1) spawning in both years of the study. Although sea temperatures were significantly higher, oysters in Cork Harbour (site 2) did not spawn but instead reached ripeness and then started a process of gametic degeneration called resorption. Lack of spawning was not attributed to environmental conditions monitored but was tentatively attributed to levels of pollutants in the water. Oyster condition in Cork Harbour was significantly affected by the presence of blistering due to tributyltin levels in the water and also by Polydora sp. (Polychaete) in the shell. Oyster condition in Dungarvan was not affected by the presence of the exotic species Mytilicola orientalis (Copepoda: Cyclopoida).

Heart rate of the tropical limpet Cellana grata was monitored on the shore (Cape d'Aguilar, Hong Kong) and in the laboratory using a non-invasive technique. Individual field measurements performed on inactive limpets, in a variety of thermal conditions during a diurnal low tide, showed a general increase in heart rate with increasing body temperature. This relationship was not always evident when monitoring individual responses over a diurnal low tide period, since under some circumstances, heart rate of individuals decreased with increasing the temperature of the substrate and foot. A factorial laboratory experiment showed that heart rate was faster at higher temperatures but slower in larger animals. The combined evaluation of field and laboratory data suggests that limpets in some habitats may be able to regulate their metabolic rate when resting on hot rock substrates.

Alepocephalus bairdii is a deep sea fish caught but discarded by semi-industrial fisheries from the north-east Atlantic Ocean. Reproductive features were investigated on 448 females of 29–93 cm standard length (SL) captured over 2 y (December 1995–December 1997) at 800–1280 m off the west coast of the British Isles. The first maturity of females was determined at L50=55 cm SL. A well-defined spawning period could not be determined in this species; a batch spawner characterized by an indeterminate annual fecundity. Absolute batch fecundity was estimated between 458 and 7049 oocytes per female 63–88 cm SL.

The great scallop Pecten maximus (Bivalvia: Pectinidae) supports a substantial European fishery with a recent history of declining catches caused by over-exploitation. The sustainable exploitation of shellfish populations requires knowledge of the extent to which commercial grounds are reproductively self-sustaining or supplied with larvae originating from further afield. The degree of genetic differentiation between locations can provide important indirect evidence, reflecting the pattern and scale of effective larval dispersal. Pecten maximus were sampled from five locations around the Isle of Man, from Mulroy Bay (Ireland) and from Plymouth. Restriction-site variation was investigated in two PCR-amplified mitochondrial DNA fragments of 2 and 3 kb, respectively. Haplotype and nucleotide diversity within populations, and nucleotide divergence between populations, were calculated. Mean nucleotide sequence divergence was corrected for within-population polymorphisms and visualized by UPGMA cluster diagrams. Molecular analysis of variance (AMOVA) was carried out. Results showed low levels of population differentiation. Slight but significant differentiation between Isle of Man populations was revealed, with East Douglas appearing distinct from the remaining Manx locations. The analyses also indicated the distinction of Mulroy Bay from the other populations, and the lowest genetic variability was recorded from this enclosed habitat. This probably reflects the relative isolation of Mulroy Bay, whereas dynamic hydrographic conditions in the Irish Sea and the Channel may generally ensure extensive mixing of the planktonic larvae.

Macrofaunal community structure was examined in a shallow sublittoral sea grass bed (Zostera marina L.) and adjacent unvegetated sediment in the River Yealm, Devon, south-west Britain, on a single sampling occasion in August 1995. The presence of Zostera had a significant influence on macrobenthic community structure in the River Yealm. Samples from inside the sea grass bed were characterized by significantly higher numbers of individuals and species, as well as by greater species richness and high faunal dominance (i.e. low evenness) compared with the unvegetated samples. High faunal dominance within the sea grass bed was attributable to the large numbers of a few species (e.g. the polychaetes juvenile capitellids, Spio filicornis, Exogone hebes, Nereis pelagica and the tanaidacean Apseudes talpa), while increased species richness was a result of a large number of additional rare (1–2 individuals) species. The greatest number of individuals was found in samples with the highest sea grass biomass. Multivariate ordination revealed a distinct separation of macrofauna communities from vegetated and unvegetated sites. Significance testing with ANOSIM shows that there were significant differences in community structure between vegetated and unvegetated habitats.

Continuous Plankton Recorder records from the North Sea and north-east Atlantic from September 1997 to March 1998 indicate an exceptional influx of oceanic indicator species into the North Sea. These inflow events, according to historical evidence, have only occurred sporadically during this century. This exceptional inflow and previous inflow events are discussed in relation to their similarity in terms of their physical and climatic conditions.