The embryos of Icelandic capelin (which spawn subtidally) tolerate as low temperatures, and are as euryhaline, as those of Balsfjord capelin which spawn intertidally. The median lethal lower temperature for Icelandic capelin eggs exposed for 6 h to low temperatures in frozen seawater films (34‰) is -6.3°C. The median lethal high salinity (6 h exposure) is 88.3‰. Eggs were reared and hatched successfully in all salinities from 1.5 to 34‰. When exposed to high salinities capelin eggs shrink in a matter of seconds (shrinkage being manifested in depressions of the chorion), but resume a normal shape in a few minutes as salts diffuse into the perivitelline fluid. Evidence is presented to show that mortality in frozen seawater films is due to osmotic dehydration, rather than to a final invasion by ice crystals. A model of freezing avoidance in capelin eggs is described.

Field data on the pelagic occurrence of Corophium volutator were obtained in 1981–82 in the Dollard (Ems estuary). The pelagic population density averaged over a tidal half cycle was in the range 0–15 m-3. The pelagic population represents about 0.06% of the benthic population. On most sampling days pelagic occurrence resulted in a net flood surplus transport.

The pinnate (feather-shaped) hydrocauli (stems) of Aglaophenia harpago are dish-shaped with the food catching hydranths borne on the convex side of the lateral branches, a morphology recognised as an adaptation to feeding from unidirectional currents. A. harpago experience unidirectional currents because the hydrocauli are able to rotate close to their bases on an articulation in the perisarc (the tubular exoskeleton) so that the concave surface always faces into the current and the hydranths face leeward. The structure of this articulation, revealed by light and electron microscopy, is described and its mechanism interpreted. The articulation consists of two oblique grooves of thin flexible perisarc which traverse around the hydrocaulus at an angle of 62–65°. The grooves terminate in areas of perisarc divided into longitudinal lamellae (probably of structural protein). The grooves and lamellae confer the flexibility which allows the hydrocaulus to ‘fold’ up to 90° clockwise or anticlockwise across each groove. The lamellae maintain the longitudinal support necessary to prevent the hydrocaulus collapsing.

A tide pool population of the brittle-star Amphipholis squamata in South Devon was monitored from July 1986 to July 1987 with respect to a number of population dynamical attributes. The population had a simple life history. Most individuals recruited into the population in the period June-September, were reproductively active in the following summer and died when 13-17 months old. The population differed from others studied in temperate latitudes in pattern of recruitment, survival and in duration of reproductive activity. We speculate that these differences are a consequence of tide-pool conditions.

The present investigation is a confirmation and extension of the idea that visual pigments adapted to the quality of their own bioluminescence have evolved in certain deep-water marine fishes. In this case a single fish (Malacosteus danae) of the family Malacosteidae, known to have red-emitting photophores, was trawled up in daylight from the Pacific off the coast of Southern California. Retinal extractions were found to contain two photopigments with absorbance maxima, one at 556 nm, the second at 514 nm. From the spectral positions of the oximes formed by bleaching in the presence of hydroxylamine it was inferred that the 556-pigment is an A2-pigment and the 514-pigment, an Aj-pigment. Evidence was also obtained from the effect of hydroxylamine on the unbleached extract of the possible presence of a photopigment that was bleached by the daylight when the fish was brought to the surface. This pigment, also identified as an A,-component from the oxime spectrum, could have been a moiety of the 514-photopigment but the possibility of a third visual pigment in the retina of this fish cannot be discounted. Except for this hydroxylamine effect the results are in agreement with published data from Aristostomias scintillans.

The three lobed paragnath of Palaemon serratus (Pennant) contains numerous rosette-type tegumental glands often arranged in clusters of up to ten glands. Each gland is made up of around ten cells most of which stain deeply with toluidine blue and whose contents have a reticulate appearance in electron micrographs. One, or occasionally two, cells stain faintly and have a fine granular appearance in electron micrographs. The central region of each gland contains the main drainage duct together with feeder canals from the vesicular storage areas. The actively secreting region of each cell is peripheral and typified by abundant rough endoplasmic reticulum and Golgi apparatus. There are nerves adjacent to the glands and their contents are probably discharged in response to a food stimulus. The structure and possible function of the glands are discussed in relation to those of other species The secretions could act as a lubricant and as a binding agent to aid in the ingestion of particulate food. There is no evidence for any direct digestive function.

Populations of Odostomia eulimoides Hartley were sampled from mussel beds on an exposed rocky shore at Preghane Point on the south coast of Ireland from April 1984 to October 1985 and from sublittoral farmed mussels at Bantry Bay on the south west coast of Ireland from March to October 1986.

At Preghane Point O. eulimoides had a area-annual life cycle with summer-autumn recruitment. Peak recruitment occurred from May to July in 1984 and from July to September in 1985. This aphasic recruitment was explained by the lower mean adult shell height recorded from April to June 1985 than in these same months in 1984.

Previous field studies have recorded yearly variations in fecundity of 40–60% in similar sized plaice, and an experiment was conducted to investigate whether these changes could be generated, in the laboratory, by feeding plaice different levels of ration. One group of plaice was fed at a rate of about 2–2.3% of wet body weight per day, and a second group was fed initially 0.5% and later 1.8% per day. The experiment lasted for a period of 406 days.

Of those fed on the lower ration, 39% produced no granular oocytes, whereas all fish on the higher ration produced granular oocytes. A comparison between the two groups, of those which did produce granular oocytes, found that the better-fed fish had 59% more granular oocytes, but the differences were less pronounced for the smaller, mature fish. Numbers of resting oocytes are also recorded.

The results suggest that food level can significantly affect fecundity, and also revealed a new mechanism for regulation of fecundity in the plaice. The lack of granular oocytes was not due to atresia, but to an early decision not to proceed with gonad development; whether this is of practical significance for the population of plaice in the wild is not yet established.

A new species of free-living marine nematode, Terschellingia gourbaultae sp. nov., from the Tamar estuary, south-west England, is described and illustrated. This species has also been recorded from Brittany, France. T. daviger, sensu Gerlach (1963) nec Wieser (1956) is a junior homonym and is re-named T. maldivensis sp. nov. Five Terschellingia species including the new species are distinguished by their lack of a distinctly offset, rounded oesophageal bulb; a table and figures are given to aid identification of these species.

Variations in dry body weight in the Stage V copepodite, associated with the development of the winter generation of Calanus finmarchicus (Gunnerus) in the Firth of Clyde each year were observed from 1978 to 1982, during early October and the middle of January.

The Stage V copepodite was dimorphic with respect to body size. Body weights of freeze-dried specimens were measured and form was distinguished using the prosome length. Allometric relationships of the dry weight to length in the two forms were similar, and stable between autumn and winter. From the mean of estimates for all collections, dry body weights of individual Stage V copepodites were proportional to the cube, approximately, of prosome lengths. Proportional coefficients were seasonally variable, but on all occasions these were greater for the large than the small form. Variations in dry weight were directly associated with the distinction between forms in body volume.

Collections from October and January encompassed the period between the end of maximal Copepodite V recruitment and the onset of adult recruitment to the winter generation. Over this period, however, the dry body weight in all years decreased relative to length in Copepodite Stage V. This decrease, on average, was by 17% and 23% in the large and small forms respectively. Monthly collections from one population were used to examine these patterns in relation to the development of gonads. Stage V copepodites of both forms were increasing in dry weight during October, but from November were losing weight continuously. Maturation in the majority of these individuals was restrained throughout autumn, abruptly accelerating in winter.

Between 1980 and 1985 ninety-seven stations were sampled by Smith-Mclntyre grab from the offshore northern section of the North Sea. Four hundred and nine infaunal species were identified from the 76 selected macrofaunal stations. The number of species per station varied from 25 to 80 with a maximum abundance of 9,600 individuals m−2. The biomass ranged from 0.13 to 18.86 g dry weight m−2. At most stations, however, biomass varied between 1 and 4 g dry weight m−2. Diversity and abundance were highest in the 120–140 m zone, characterised by fine sand containing variable amounts of silt. The highest biomasses were recorded in two areas; firstly where stronger currents predominate and the sediments are coarser (east of Shetland and west of the Norwegian Trough), and secondly in the fine sandy deposits of the centrally located area. In the silty sediments (Fladen Ground and smaller depressions) there was a predominantly subsurface deposit-feeding community, whereas in the coarser area east of the Shetlands carnivores predominated. Over the remaining area surface deposit feeders were dominant.

Records of fish captures on power station intake screens were used to analyse the structure of the English and Welsh inshore fish community. The study was undertaken as part of a programme to predict fish captures at future power station sites. It was found that 118 of the 122 fish species known to live inshore were recorded from the screens of 12 coastal power stations. The maximum number of species at one site was about 80, achieved at fully marine localities along the English Channel coast. This number declined with increasing latitude and decreasing salinity.

Fish subdivide their use of the inshore habitat both spatially and temporally and the proportion of species complement within the major subdivisions of the habitat was remarkably similar at all sites. On average, 28 species were present simultaneously and these would include 4 pelagic, 8 demersal and 16 benthic species.

Bacteria have been isolated into pure culture from the gills of Lucinoma borealis, Myrtea spinifera, Thyasira flexuosa and T. sarsi collected from several British and Scandinavian coastal sediments. It is proposed that these bacteria are symbiotic with the animals. The bacteria were either autotrophs, obtaining energy from oxidation of inorganic sulphur compounds, or methylotrophs using methanol or methylamine as the source of carbon and energy. The latter could also oxidize thiosulphate to tetrathionate and precipitate elemental sulphur. The pure cultures have been characterised in some detail, showing that (1) their DNA base composition falls in the range 47–58% guanine + cytosine; (2) although all grow well at the natural environment temperatures of 8–15°C, their optima lie between 30 and 35°C; (3) all produce copious amounts of extracellular slime when grown at low temperatures; (4) the autotrophic isolate is facultatively heterotrophic, containing a repressible ribulose bisphosphate carboxylase, and excreting up to 30% of its carbon dioxide fixation into the culture medium; (5) the methylotrophs include some containing high activities of hexulose phosphate synthase for assimilation of formaldehyde by the ribulose monophosphate cycle; others may have novel assimilatory metabolism. The possibility is discussed that environmental factors may determine whether a methylotroph-animal or autotroph-animal symbiosis is established rather than the symbiont type being an invariable species-specific character.

Comparison of early shell morphological features of six mytilids from the north-western Atlantic revealed differences useful for species identification and classification. Brachidontes exustus, lschadium recurvum, Geukensia demissa, Amygdalum papyrium, Mytilus edulis, and Modiolus modiolus larvae and post-larvae were cultured in the laboratory. Scanning electron micrographs of the shell and hinge during early ontogenetic stages showed that all species had a long provinculum with taxodont dentition. In addition, provinculum length and number of teeth increased during the larval period in the six species. The small, numerous provincular teeth of Mytilus edulis and the bold, comparatively few provincular teeth of Amygdalum papyrium clearly differentiated these two species. Most species had a low umbo, round posterior margin, and more pointed anterior margin, although Amygdalum papyrium was distinguished by a high, prominent umbo. Distinction of Geukensia demissa and lschadium recurvum larval shells was difficult due to similarity in their shapes and hinge dentition. However, discriminant analysis using larval shell length, shell height, provinculum length, and number of teeth aided in classification of these and other sympatric species.

Previous studies with the marine gastropod Littorina littorea have shown that cadmium is concentrated in the digestive gland and that cytosolic metallothionein-like proteins sequester a large proportion of the accumulated burden. In the current investigation, an electron microscope cryo-preparation method and X-ray microanalysis have revealed that some cadmium, in association with sulphur, is localised in the region of the limiting membrane of the mineralised granules which detoxify certain metals as an insoluble phosphate salt. It appears, therefore, that there could be interaction between the sulphur and phosphate systems for binding metals within the basophil cells of the digestive epithelium.

Samples of phytoplankton from nets towed in the surface waters off Plymouth over a period of 24 years were subjected to a correspondence analysis. There was a high species diversity throughout the year, and a strong seasonal cycle. A total of 104 species was divided into eight groups showing different seasonal and year-to-year occurrence. Over the 24 years the seasonal pattern of species changed in a fairly systematic way and there were two periods (1968–70 and 1983–85) when the changes were most marked. These patterns could be related to changes in the weather patterns, and were similar to those found by other workers in other groups of organisms and in other areas.