The tropical surf barnacle Tetradita squamosa (Bruguière) (Crustacea: Cirripedia) has a pair of lobulate digestive glands each connected to the dorsal surface of the foregut by a single duct. These glands have a central lumen surrounded by columnar epithelial cells and are the primary site of enzyme synthesis and secretion within the alimentary tract. A number of carbohydrases and proteases were detected, all of which exhibited optimal activity at an acidic pH. Gland cells discharge secretory products into the foregut ventriculus via apocrine secretion and this process is continuous; it is not correlated with tidal and subsequent feeding cycles. Possible reasons for the absence of feeding and secretory co-ordination are discussed.

Magnesium/chlorine and sulphur/chlorine ratios have been measured in the body fluids of some planktonic organisms by x-ray emission analysis of frozen hydrated specimens in a scanning electron microscope. Homarus vulgaris (Anthropoda: Decapoda) larvae excluded Mg2+ and SO42-ions from the haemolymph, but to a lesser extent than does the adult lobster. Bipinnaria larvae of Asterias (Echinodermata) excluded Mg2+ and SO42-ions from the coelomic fluid. Obelia medusae excluded Mg2+ and SO42-ions from the mesogloea but concentrate them in the gastrovascular system. The high concentration of sulphate in the gastrovascular fluid of medusae has been confirmed by rhodizonate titration in Cyanea and Rhizostoma jellyfish. Some implications of magnesium and sulphate regulation are discussed.

It appears that, under suitable conditions, diatom assemblages can respond very quickly to a toxic event. The data suggest an inoculum of cells from the water column can multiply rapidly. Sediment-inhabiting macrofauna are more seriously affected, reducing grazing restrictions on the developing diatom assemblages. The structure and behaviour of the sediment was intimately related to biological factors including bioturbation and biogenic stabilization in a complex and interdependent manner. Further work is now required on the interaction of grazing organisms and microbial communities in the dynamics of intertidal cohesive sediments.

Fifteen marine strombidiid species were measured and identified after protargol staining of bottle-cast samples collected during an annual study of the ciliate microzooplankton in the Caribbean Sea. Nine of these are described herein as new species. One new species from the genus Tontonia, T. simplicidens sp. nov., is defined, based on the pattern of the girdle and ventral kinety. Six new species of Strombidium, S. bilobum sp. nov., S. eurystomum sp. nov., S. ioanum sp. nov., S. maedai sp. nov., S. pollostomum sp. nov. and S. sphaericum sp. nov. are defined, based on cell size and shape, the arrangement of the oral ciliature, and the nature of the macronucleus. One new strombidiid genus Cyrtostrombidium gen. nov., is defined by the presence of a unique oral ‘basket’ and the absence of the ventral polykinetidal zone. Two species of Cyrtostrombidium, C. longisomum sp. nov. and C. wailesi sp. nov., are distinguished, based on cell size and macronuclear structure. Assemblages of six previously-described strombidiid species, S. constrictum, S. dalum, S. epidemum, S. inclinatum, S. wulffi, and Laboea strobila are also briefly described.

Heterotrophic protists, mostly flagellates, encountered in association with marine detritus from various collections in the mid North Atlantic are described. About 40 species have been identified and are reported. Taxa reported here for the first time are: Caecitellus gen. nov. (Protista incertae sedis) and Ministeria marisola gen. nov., sp. nov. (Protista incertae sedis). The flagellates form a subset of the community of heterotrophic marine flagellates encountered in more productive marine sites. Most species are bacterivorous and small. The community extends to the ocean floor but the diversity is reduced in samples taken from greater depths. The decline in species diversity is linked also to a decline in numbers of individuals. We discuss these changes in relation to food supply and pressure effects.

The calanoid copepod Temora longiornis (Müller) has sub-cuticular secretory glands located on both the body and swimming legs. The glands are tri-cellular, consisting of a secretory cell (producing a proteinaceous secretion) opening through a cuticular pore, a collar cell surrounding the neck of the secretory cell, and a duct cell which lines the pore opening. The possible function of the secretion is discussed.

The relative abundance of the six copepodite stages (CI-CVI) of Calanus helgolandicus Claus (Copepoda: Calanoida) and Pseudocalanus elongatus Boeck (Copepoda: Calanoida) was recorded at a station in the English Channel throughout 1989. There was a pronounced seasonal variation in the abundance of the early stages. Increased recruitment from the nauplii corresponded in both species to rising primary production early in the year, producing small CI abundance peaks in March. The major period of naupliar development occurred after the April/May spring bloom. During seasonal peaks the CI and CII stages typically formed 40% of the copepodites of these species but were scarce at other times. The body carbon weight of Calanus and Pseudocalanus CIs decreased by 38% and 21% respectively from May to August, indicating an increase in food limitation for the nauplii. Summer was passed predominantly in the CIV and CV stage at low abundances.

Observations were made on the reproduction and life history of five species of polychaetes collected from the continental slope off North Carolina, USA. Three species were studied at a 2000-m lower slope station off Cape Lookout (Aurospio dibranchiata, Microrbinia linea, and Pholoe anoculata) and the other two at a 600-m upper slope station off Cape Hatteras (Cossura longocirrata and Scalibregma inflatum). Aurospio dibranchiata, a surface feeding spionid, exhibited seasonally in egg diameter and size-frequency data, with the larger sizes occurring in late summer months. Pholoe anoculata, a small carnivorous scale worm, did not exhibit any evidence of seasonality in size-frequency data at the 2000-m station. Sexually mature specimens were absent from this population, but were present at shallower slope depths, indicating year-round recruitment into the lower slope from middle and upper slope populations.

Between 1983 and 1989,66 stations in the north-eastern Irish Sea offshore from Sellafield, Cumbria, were sampled by Reineck box corer to assess the abundance and distribution of the benthic macro-infauna. A total of 40 taxa was identified, of which the predominant group was polychaetes. Cluster analysis of the abundance data showed a division into three station clusters. Simple discriminant analysis showed that the three clusters were correlated (P<0.01) with sand, silty sand and sandy silt sediments. However, the three station groups did not show any clear pattern of characterizing taxa with sediment classification. The bioturbating potential of each taxon is reviewed. A method of weighting abundance data by a factor representing an estimate of individual taxon bioturbating potential is also suggested. This technique is illustrated and discussed by using the weighted data in a further cluster analysis to identify probable areas of high inf aunal bioturbation off Sellafield.

Spatial, seasonal and age-related differences in infection of the cockle, Cerastoderma edule, with the trematode Meiogymnophallus minutus were studied on the Exe Estuary, England. Prevalence of infection was 100% across all samples with mean abundances between approximately 300 and 1000 larvae per host (maximum=4930 larvae). Aggregration of M. minutus in cockles was extremely high (variancermean ratios >100) and increased linearly as abundance increased. Mean abundance was highest in cockles collected from muddy substrates where the average age of cockles was high. In summer, numbers of larvae fell to less than half of spring levels and then increased after infection by a new wave of cercariae in August. Cockles accumulated larvae for up to 2 y but not thereafter, and levels of aggregation fell in the oldest age class. A peaked pattern of mean abundance and aggregation with age may be a result of parasite-induced death of older hosts or may be due to the inability of cercariae to establish in older hosts.

Although the English Channel is the northern limit of the latitudinal range of Sphaerechinus granularis (Echinodermata: Echinoidea), this echinoid can produce locally high densities in Brittany, such as in the Glénan Archipelago (Bay of Concarneau) where a small-scale fishery has been exploited since 1985. The reproductive cycle, the growth patterns and the migration of the species in this area were studied from 1988 to 1992. Sphaerechinus granularis presents an annual reproductive cycle with a major spawning in the early spring. But inter annual variability in the time when spawning starts can be observed. A relationship is established between the date of onset of spawning and the climatic conditions during the whole period of gonadal growth. Recruitment is isolated in time and reflects the reproductive cycle.

Diets of the two deep-sea species of Mediterranean oplophorids were studied by the analysis of 244 foregut contents of Acanthephyra eximia and 69 of Acanthephyra pelagica. All the specimens were collected on the deep slope (between 610 and 2261 m) using an OTSB-14 bottom trawl.

The diet of A. pelagica consisted of small mesopelagic fishes (Cyclothone braueri, Myctophidae) and bathypelagic crustaceans (Gennadas elegans, Pasiphaea multidentata, Eucopia hanseni, Meganyctiphanes norvegica, hyperiids). In contrast, A. eximia was an important scavenger, feeding on fish remains. Benthic species (polychaetes, Calocaris macandreae, gastropods, etc.) were also detected in its diet. There was little dietary overlap between the two species. In A. eximia bathypelagic decapods were important only in the diet of large specimens. In small specimens the acquisition of decapod prey was not attributable to active hunting. On the lower slope A. eximia was more detritivorous, and predatory activity was lower. This trend was most distinct in small and medium-sized individuals, which predominate at that level.

First-stage zoeal larvae of the green (shore) crab, Carcinus maenas (Crustacea: Brachyura: Portunidae), ingested three types of particles offered in sea-water suspensions. In experiments using two types of fluorescent particles (1–2 µm and 1–7 µm ) and living Dunaliella tertiolecta cells (5–7 µm), particles were ingested in at least 40% of the zoeae examined with brightfield, darkfield, and epifluorescence microscopy. These results suggest that green crab larvae may be capable of utilizing planktonic particles in the size range of bacteria, small algal cells, and organically-enriched detrital particles in their natural diet.

A new species of lugworm Arenicola defodiens sp. nov. (common name ‘black lug’ or ‘runnydown’) is described from 148 specimens taken from intertidal sands around South Wales. Comparisons are made with the well-known and generally more common lugworm Arenicola marina (L.). To aid in diagnosis, a table illustrating differences in the genetics, ecology and morphology is also provided.

The relative contributions of the eye, pigmentation (melanophores), and gut contents to the lateral body areas of herring larvae, Clupea harengus L., were measured using a combination of photography and computer image analysis. There was a power relationship between body area and body length (exponent 2.62) which was similar to that of the eye area (exponent 2.57) whereas the pigmented area increased at a greater rate (exponent 4.41). The area of the full gut relative to body length increased at an intermediate rate (exponent 3.04). Melanophores dilated under the effects of anaesthetic, increasing the projected pigment area of herring larvae by an average of 94% after 10 minutes of anaesthesia. These results are discussed in relation to the vulnerability of herring larvae to visual predation.

Ensis directus (Bivalvia: Solenidae) was noted for the first time along the French coast of the North Sea in June 1991. High numbers of post larvae after a period of northerly winds indicate that settled larvae originated from adult populations in Belgian or Dutch coastal waters. Future dispersal of Ensis directus could be used as a biological tracer of coastal water movements between the Southern Bight of the North Sea and the English Channel.

The American jack knife clam, Ensis directus (Conrad, 1843), synonym Ensis americanus (Binney, 1870)sensu van Urk (1964,1972), was discovered in Europe in the German Bight for the first time in June 1979 (Von Cosel et al., 1982). This species is assumed to have been transported in its larval stage by a ship containing ballast water. Considering the dimensions of the specimens, this probably happened in the first half of 1978 (Von Cosel et al., 1982; Mühlenhardt-Siegel et al., 1983). Since then this species has spread rapidly in the North Sea in subtidal and intertidal areas. Dense populations were found along the German coast within a few years (Von Cosel et al., 1982; Mühlenhardt-Siegel et al., 1983; Swennen et al., 1985). In 1986 Ensis directus was reported from the north and east Danish coasts as far as the Belgian coast (Kerkhof & Dumoulin, 1987) (Figure 1). Since then no new records have been reported.

Histochemical techniques were used to investigate the possible role of the buccooesophageal glands in the blue mussel, Mytilus edulis L. (Mollusca: Bivalvia). No activity was observed for any of the eight major digestive enzymes tested; however, the glands contained large amounts of both neutral and acid mucopolysaccharides. These results confirm the importance of mucus in the ingestive process in M. edulis, and do not support the hypothesis of ingestion of particles suspended in water alone.

Until recently it was thought that the Bivalvia were the only class of molluscs in which some type of secretory gland of extracellular digestive function in the bucco-oesophageal region was totally absent (Table 1). However, in a study of the mode of particle ingestion in five species of suspension-feeding bivalves, an extensive glandular complex was reported in the bucco-oesophageal region of Mytilus edulis L. only (Beninger et al., 1991). Although these glands were observed to liberate secretions into the oesophageal lumen, it was not known whether they performed any digestive function.

Previously unknown in Conus (Mollusca: Gastropoda) and poorly documented in the Australian region, imposex is demonstrated in 80% of females of six Conus species from Rottnest Island, Western Australia. In no case were the effects sufficiently severe to cause sterility, and reproduction appeared normal. Specimens from the same location preserved in 1975 were unaffected. With more than 500 species, Conus is the largest genus of marine molluscs. Because many species are conspicuous, widely distributed, and occur in populations whose past densities are known, they could serve as monitors of artificially induced pseudohermaphroditism and an early warning of future population responses to pollutants in marine environments at low latitudes.

Daily increments were demonstrated in the sagittae of the lesser sandeel, Ammodytes marinus, maintained in outdoor enclosures. Daily increment formation was also inferred for wild sandeels from an analysis of changes in age composition within a series of field samples. A comparison between sagitta microstructure and morphological development of larval and juvenile sandeels indicated that the first sagitta increment was formed around the time of hatching. Yolk-sac absorption and larval metamorphosis were accompanied by changes in otolith microstructure.

The lesser sandeel, Ammodytes marinus (Raitt), is important as a prey item for many species of fish, seabirds and marine mammals (Furness, 1990) and supports major fisheries in the North Sea (Anon., 1991). However, little is known about the ecological processes affecting year-class strength in this species. Otolith microstructure has been demonstrated to be a potentially useful tool for investigating early survivorship in fishes, since otoliths may provide a chronological record of early growth and life-history events (see Campana & Neilson, 1985). This paper examines the usefulness of otolith microstructure for studies of sandeel growth, from investigations of increment periodicity and a comparison between otolith microstructure and morphological development.

In a short communication Grahame et al. (1992) argue against our finding that Littorina neglecta Bean is an ecotype of Littorina saxatilis (Olivi) rather than a separate species (Johannesson & Johannesson, 1990b). Unfortunately, Grahame et al. (1992) have miss-represented our earlier paper, and we feel the need to refute their arguments.

In populations from north-western Europe we studied morphological characters used to separate Littorina neglecta from L. saxatilis. We found that intermediate shapes were common and, furthermore, we found no close coupling among characters used to define L. neglecta (Johannesson & Johannesson, 1990a). We further analysed the genetic variation in five strongly polymorphic allozyme loci. In four loci we found a pattern that indicated that L. neglecta is not reproductively isolated from L. saxatilis. In the fifth locus, Aat-1, we found consistent differences between populations of L. neglecta (from the low shore) and L. saxatilis (from the high shore). Similar differences were observed between low and high shore populations in Sweden where, however, no snails of neglecta-type were present.