Series of sequences of SEM micrographs are presented to elucidate species-specific shell features in larval and post-larval stages of four Ostreidae (Bivalvia) species (Crassostrea gigas (Thunberg), C. virginica (Gmelin), Ostrea edulis L., and O. equestris Say). The diagnostic characters, including hinge structure, shell shape, and the dimensions of the prodissoconch, are identified and summarized in a key at both generic and species levels. In larval Crassostrea the skewed, backwards-pointed umboned shells with two hinge teeth on each side of the provinculum are significantly different from the round, dorsally-directed umboned shell with fewer, remarkably asymmetric teeth of larval Ostrea.In C. gigas the dimensions of the provinculum are longer and narrower (56x10 µrn) than those of C. virginica (50x14 µm); the lengths of prodissoconch I and the provinculum are greater in O. edulis (168 µm and 86 µm, respectively) than in O. equestris (120 µm and 74 µm, respectively). The present study suggests that precise quantitative measurements are needed for differentiation of the studied congeneric oyster species.

The south to north development of the spring bloom in the North Atlantic Ocean was observed during four cruises from April to August 1989. Transects with towed undulating instrumentation packages and CTD profiles on station were made between 42°N and 54°N, along 17°W and 20°W in April and between 47°N and 60°N along 20°N in May, June and July/August, giving vertical sections of temperature and chlorophyll concentration derived from in vivo fluorescence. These sections show the relationship between the onset of seasonal stratification and the initiation of the spring bloom. Supporting data from microscopic analysis of the major phytoplankton species show that the seasonal succession commenced with diatoms, followed in turn by coccolithophores, flagellates and dinoflagellates. During the development of summer stratification the mesoscale distribution of chlorophyll was strongly determined by the depth of the mixed layer, but once stratification had been firmly established higher chlorophyll values tended to be found within the warmer eddies (meanders). One possible explanation of this result is that phytoplankton growth is higher in the warmer eddies.

During the summer of 1990 the sublittoral communities on hard substrata were investigated at 32 localities off Orkney and St Abbs (Scotland). The environment in both places has an open coast character, with small seasonal fluctuations in temperature and salinity and a high transparency of the water. The major governing environmental factors are the available amount of daylight and the degree of exposure to water movement. For the photic zone two different communities, dominated by foliose algae, are described. Under exposed conditions a widespread community is found, dominated by red algae in the middle structural layer and characterized by a dense canopy of Laminaria hyperborea. Under more sheltered conditions a community occurs in which brown and green algae become more abundant in the middle structural layer, while the top layer is formed by Laminaria saccharina and Saccorhiza polyschides. In the aphotic zone, under exposed conditions, a community is found which consists of a number of variants, with a dominance of the suspension feeders Pomatoceros triqueter and Alcyonium digitatum or bryozoans and hydrozoans. These variants are found in different regions, depths and angles of inclination of the substrata. Comparable variants have also been found off Helgoland (German Bight). Under sheltered conditions the suspension feeders become of minor importance and the community is dominated by encrusting red algae. In a surge tunnel in the photic zone off St Abbs Head, a community dominated by Dendrodoa grossularia and Clathrina coriacea is present.

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.

The hyperbenthic mysid, Boreomysis nobilis G.O. Sars, 1879 (Malacostraca: Peracarida), is reported from nine new locations around the island of Newfoundland in eastern Canada. It is commonest within and at the mouths of deep fjords and is less common or absent outside these fjords. Its absence from two bays where the depths, temperatures and salinities are all within the range inhabited by B. nobilis in other bays indicates that other factors are probably influencing local distribution patterns. The catch rates for B. nobilis are highest in the deep water within 150 m of the bottom. However, no differences were found in the vertical distribution of the different life-history stages of B. nobilis and no evidence was found for large-scale diel vertical migrations. Boreomysis nobilis was found to breed throughout the year, since all developmental stages were present on all sampling dates. However, there was a period of increased breeding activity in the late spring and early summer. An examination of the relationship between brood size, body volume of ovigerous females, and number of stage 1 larvae indicates that B. nobilis produced a smaller number of larger larvae than expected for epipelagic and coastal mysids

The small bivalve Abra tennis (Montagu) (Bivalvia: Semelidae) reaches the north-eastern edge of its range in the Wadden Sea near the Dutch/German border. In the Wadden Sea it is restricted to a narrow intertidal zone close to the high-water level. Data are reported from a population at Balgzand, in the south-westernmost part of the Wadden Sea, which has been monitored for two decades. This population showed a strongly fluctuating density and was seemingly absent for more than three years following three severe winters in succession. Over-winter survival in adults was greater during mild than cold winters, and close to zero during all winters that were colder than average. Recruitment was higher in warm than in cold summers. Growth was more rapid in warm than in cold spring-summer periods. In warm years growth rates were higher than in more southern locations, and values for maximum size and life span were relatively high.

Species of Chrysochromulina (Prymnesiophyceae) were screened for their ability to ingest inert material and live cells of a small green flagellate. The species C. brevifilum showed a marked preference for the small green flagellate over carmine particles and the rate of ingestion of the flagellate was proportional to its concentration and inversely proportional to light intensity. Ingestion was also higher by phosphate-starved Chrysochromulina, and a clear predator/prey relationship was demonstrated with C. brevifilum clearly benefiting, in terms of growth rate, from the ingestion of the small green flagellate. Electron micrographs confirmed that digestion occurs.

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.

Diet and food resources of marine-feeding otters (Lutra lutra, Mammalia) were studied along the coast of central Norway, where otters breed in all seasons. The fish and crab fauna in the 0–10 m depth zone where otters forage were sampled and otter spraints collected monthly for three years. Results were compared with published data from Shetland where otters breed mainly in summer. Most of the main prey species showed significant seasonal variation in numbers or biomass, which tended to be low in late winter or spring. The variations during the rest of the year were not synchronized between species. The combined density of the main prey species of Shetland otters, which peaked during summer, was low in Norway. This species group, eelpout (Zoarches viviparus), butterfish (Pholis gunnellus) and rocklings (Ciliata sp., Gaidropsarus sp. ), also constituted a smaller fraction of the total catch in Norway than in Shetland.) and bullrout (Myoxocephalus scorpius), constituted a larger fraction of the catch in Norway than in Shetland. Thus the otter's food resources on the Norwegian coast were seasonal, being minimal during the early months of the year, but with no clear maximum season as there is in Shetland. This may explain the differences in reproductive timing in the non-seasonal or autumn and winter species, cod (Gadus morhua.

Seasonal and annual variations in the distribution and abundance of echinoderm larvae (early to post-larvae of principally echinoids and ophiuroids), were determined from a series of plankton net tows taken at three stations in the Bay of Villefranche (France) and along a radial transect of 28 nautical miles (52 km), from the Bay to half-way to Corsica, between 1984 and 1988. Spatial distribution of six echinoderm species have been mapped. For the echinoids, Paracentrotus lividus and Arbacia lixula, spawning takes place twice a year and appears to be synchronous because larval cohorts were comprised of distinct age-classes both near and far from the coast. Recruitment for these species is, therefore, thought to occur at well-defined periods. In contrast, the ophiuroid species studied (Amphiura filiformis, Ophwthrix fragilis, Ophiopluteus bimaculatus and O. compressus) spawn several times per year with a relatively short period in late spring and a prolonged spawning between the end of autumn and winter. These later results are consistent with the presence of mixed size-classes of larvae either from the nearby coast or offshore. Recruitment for these ophiuroids appears to be much more variable and spread over time.

The life cycle, seasonal dynamics and production of two populations of Streblospio species (Annelida: Polychaeta), S. benedicti Webster, 1879, from muddy sediments of the Great Sippewissett Salt Marsh (southern New England, USA), and S. shrubsolii (Buchanan, 1890), from muddy areas of the Alfacs Bay (north-eastern Spain), were studied from November 1986 to September 1988. Both species have life-cycles shorter than one year. The American population showed a unimodal distribution most of the year while in the European population polymodal distributions were common. Average density of S. benedicti over the two-year period ranged from 24,086 to 677 individuals m−2 (annual average 4,554). The observed numbers of S. shrubsolii ranged from 65,668 to 2,579 individuals m−2 (average 35,311). The biomass of the American population ranged from 2·1 to 0·04g dry weight m−2 (average 0·5). The values obtained for the European population ranged from 5·9 to 0·1 g dry weight m−2 (average 4·1). Secondary production was higher in the European population (15·65 g dry weight m−2 y1) than in the American population (3·0 g dry weight m−2 y−1). Production to mean biomass ratios were 4·4 y−1 for S. shrubsolii and 5·4 y−1 for S. benedicti. Population densities are compared with previously published data for other Streblospio populations.

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.

Settlement and growth of Melarhaphe neritoides (L. ) were studied on two rocky shores, at Carnsore Point, County Wexford and Tragumna, County Cork, on the south coast of Ireland during the years 1977–1978 and 1983–1991 respectively. Settlement occurred in each year but varied in timing and density, with maxima of 30,000 m-2 at Tragumna and 3,800 m-2 at Carnsore Point. Recently settled individuals occurred in pools in the Verrucaria zone and on open rock below this level. Growth of the 0+ and 1+ cohorts was determined by analysis of length frequency distributions. Growth of older snails was estimated by measuring growth increments in marked animals. Recruits grew to less than 2 mm in shell height in their first year. Larger snails (>2 mm shell height) grew 0. 2–0. 3 mm shell height per year. It is estimated that M. neritoides takes over five years to reach a shell height of 3 mm at Tragumna.

In order to elucidate the ecological significance of polychromatism in Idotea baltica (Crustacea: Isopoda), the distribution of the various phenotypes was studied for three consecutive years in a population from the Bay of Naples. The most abundant morphs were uniformis (males: 394%-100%; females: 24·6%-84·1%) and maculata (males: 0·59·8%; females: 0%·50%), their distribution varying throughout the year. The assessment of some biological characters (females size, fecundity and embryonic stages of development) did not show any differences accounting for preferential fitness of these phenotypes. Moreover, it was observed that phenotypic diversity in colour morphs followed seasonal changes in the substrate composition. In agreement with other investigators, it has been suggested that the camouflage function of polychromatism may have a fundamental role in the reduction of predation, and favour Idotea baltica colonizing a variety of changeable habitats.

The reproductive biology of two epizoic deep-sea anemones reveals contrasting reproductive strategies. Amphianthus inornata (Cnidaria: Anthozoa) lives attached to the bathyal gorgonian Acanella arbuscula (Cnidaria: Anthozoa). Females of A. inornata increase in wet body weight as a result of increased oocyte production until 40% of the body weight is reproductive tissue. The anemone reproduces on a seasonal basis, releasing eggs in the early spring of each year. By contrast, Kadosactis commensalis (Cnidaria: Anthozoa) lives attached to the body wall of the abyssal holothurian Paroriza prouhoi (Echinodermata: Holothurioidea). This anemone is a protandric hermaphrodite, females being found only at the anterior end of the holothurian, whilst males are found at any point on the host. Females have a significantly higher wet weight than males and neither sex shows any reproductive seasonality.

One hundred and twelve Pycnogonids belonging to 18 species are recorded from waters of 12–490 m depth on both sides of the Straits of Gibraltar. Twenty-three specimens are Mediterranean (8 species) and 89 are Atlantic (14 species).

Hannonia stocki and Ammothella gibraltarensis are new species. Pentapycnon geayi is new to European waters and Pycnogonum nodulosum, Ammothella biunguiculata and Callipallene spectrum are new from southern Spanish waters.

A total of 38 species has now been reported for southern Spain.

INTRODUCTION

There are only two published papers on pycnogonids from southern Spanish waters: Munilla (1988) reported on mediolittoral and shallow-water taxa (0–12 m), with 11 species collected, while Stock (1987) recorded 20 species from deeper waters (135–2110 m).

The present collection of 112 specimens, from shallow to moderately deep waters, was carried out in July 1989 aboard the B/O ‘Garcia del Cid’ during the Project FAUNA 1, conducted by the Museo Nacional de Ciencias Naturales in Madrid (CSIC).

Changes in the composition of the diet, foregut fullness, and the degree of digestion of ingested food were taken into account in determining diel feeding activity of the numerically dominant species of decapod crustaceans dwelling on the Catalan Sea Slope (western Mediterranean). Two 24-h periods were sampled at two different stations on the upper middle slope (between 400 and 710 m) using bottom trawls. Additional foregut fullness data for Aristeus antennatus and Acanthephyra eximia were recorded below 1000 m. The influence of the relatively shallow-living mesopelagic fauna (Pasiphaeidae, Sergestes arcticus, euphausiids, and fishes) over the 24-h cycle apparently had a large effect on the feeding activity rhythms in the deep-sea decapods studied. Species can be classified into two different groups according to their feeding patterns. Thus, species whose diet was based on pelagic prey (Plesionika edwardsi, Plesionika martia, and A. eximia) exhibited a feeding pattern conditioned to the availability of this type of prey. In contrast, in those species in which pelagic prey contributed only a small portion of the diet (A. antennatus, Plesionika acanthonotus, Polycheles typhlops, and Geryon longipes) no variations in the foregut fullness or in the percentage of undigested prey in foreguts during the diel feeding cycles were recorded. The decrease in the influence of the abundance of mesopelagic fauna with depth, with a commonly accepted boundary at around 1000 m would be responsible for the progressive flattening out of activity rhythms among the species dwelling on the lower slope. Foregut fullness values for certain species with broad depth distributions in the Catalan Sea (A. antennatus, A. eximia), would support this hypothesis.

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 effects of cell concentration on colony growth and feeding behaviour were investigated in the polymorphic marine bryozoan Celleporella hyalina (Bryozoa: Cheilostomata) under controlled, laboratory conditions. We compared the relative zooidal composition of colonies cultured on Rhodomonas baltica (Karsten) for seven weeks at 18°C. We observed the pharynx of active lophophores on sudden exposure to high cell concentrations, and recorded the length of feeding episodes and ingestion rates.

Colonies grew, reproduced and produced viable larvae at all levels of food supply, but performed optimally at 50–100 cells µl-1. Cell concentration influenced somatic parameters more than sexual, the latter being more closely associated with genotype. Relative somatic investment was greatest at 10 cells µl-1 and least at 50 cells µl-1. The frequency of ovicells containing larvae remained at about 74% irrespective of food supply. Basal male investment was greatest at 10 cell µl-1, frontal male investment at 50 cells µl-1, and female investment at 100 cells µl-1.

Cell ingestion rates of previously starved zooids increased as a function of cell concentration, with an inverse relationship between length of feeding episode and concentration. Food particles were drawn from below the lophophore by lateral cilia, ciliary reversal brought them over the mouth, and ingestion then resulted from a pharyngeal current. These results suggest that, on exposure to high cell concentrations, bryozoans may exhibit specific behaviour.