Spray-dried Nannochloris sp. and Tetraselmis suecica were fed to larvae of the Manila clam (Tapes philippinarum).

These dried diets supported growth equal to, or greater than, their live algal counter-parts, but less than a control diet, a mixture of two algae species of known high nutritional value (Chaetocems calcitrans and T-ISO).

Larvae were grown through to metamorphosis on the dried Nannochloris sp. diet in 21 days, compared with 8–11 days with the control diet. Using dried Nannochloris, it was shown that T. philippinarum larvae do not have an essential requirement for long-chain (20 and 22C) polyunsaturated fatty acids, but are able to synthesize them from shorter chain (18C) fatty acids present in the diet. The higher total carbohydrate content of the dried algae was reflected in the larvae feeding on this diet.

Unusually high densities of juvenile flatfish in some areas of a nursery ground, and complete absences from other areas, were associated with a dense bloom of the colonial alga Phaeocystis pouchetii along the coast of North Wales. A possible explanation for these movements, and for the presence of patches of anoxic sediments, is proposed.

Incidence of epibiosis has been studied in the deep-water portunid crab Bathynectes piperitus in the Benguela upwelling region. The serpulid polychaete Spirorbis cf. patagonicus, the hydroid Stegopoma plicatile and the stalked cirripede Poecilasma kaempferi were the commonest epizoitic species. Analysis revealed some biological and ecological features of the host population: the species does not have a terminal moult; both sexes show different moulting patterns; sexual maturity occurs at around 35 mm carapace length; there is asynchronous moulting among different sub-populations in different geographical areas; burying behaviour appears to be not very widespread.

Dispersion in a littoral population of Pagurus bernhardus in south-west England is shown to be random, with members demonstrating no evidence of site attachment. Movement patterns within the population are shown to be asynchronous and random, and to be dictated by the quantity and quality of each individual's shell contacts. These, in turn, affect the time that individuals spend within the habitat. This implies that population dynamics and residence times are so influenced by the availability of suitable empty gastropod shells that movement and migration in hermit crabs should be regarded as resource-dependent phenomena.

Dense populations of Prorocentrum micans are reported from the Galway Bay area in 1980 and 1981. At one location a density of llx106 cells dm-3 was found co-incident with a bright red colour in the water. High concentrations of chlorophyll a and high levels of dissolved oxygen were also associated with the blooms.

Advantages and disadvantages of methods used to estimate area of individual secondary lamellae are discussed. Particular attention is given to explain the method which regards filaments as triangles and lamellae as rectangles. Dangers of some injection methods assuming that the whole lamellar microcirculation is equally involved in gas exchange are also emphasized. It is concluded that there is a need for comparisons of results when different methods are applied to the same material.

The study of the morphological and meristic characters of larval and adult sandeels (Gymnammodytes spp.) collected off the Catalan coast (NW Mediterranean) has revealed the co-occurrence of G. cicerelus and G. semisquamatus in the Mediterranean. The geo-graphical distribution of G. semisquamatus had hitherto been thought to be limited to the European Atlantic coasts. The comparative analysis of specimens of G. semisquamatus from the Mediterranean and from the North Atlantic has demonstrated a marked latitudinal cline in the meristic counts. An exhaustive overview is presented of the bibliography referring to the Ammodytidae family in the Mediterranean, and the validity of the numerous references is discussed. Finally, it has been shown that the accepted description of G. cicerelus included the two species: G. cicerelus and G. semisquamatus. In the present paper an up-to-date diagnosis of both species is presented.

In this study the selachians were captured monthly on inshore grounds (10–30 m deep) with a beam-trawl over ten years (1975–1984), mainly in the Bay of Douarnenez, the Roads of Brest and the Bertheaume Cove area (west Brittany). Catches were composed of five species, accounting numerically for 6–5% of the mean catch of the trawled fishes, but reached up to 20% in Bertheaume Cove. On account of the adaptability to different bottom substrates Raja clavata is the most common species. Raja microocellata is uncommon except in the Cove of Bertheaume where it represented half of the selachian biomass captured.

The anatomy and behaviour of the oncomiracidia of Kuhnia scombri, K. sprostonae and Grubea cochlear, related mazocraeid monogeneans from the gill chamber of the mackerel, Scomber scombrus, caught off Plymouth are compared. K. sprostonae and G. cochlear are new records at Plymouth. The most important anatomical difference between these larvae is that those of Kuhnia spp. possess a pair of pigment-shielded eyes which are lacking in G. cochlear. The freshly hatched larvae of Kuhnia spp. are strongly photopositive but this response wanes after about 1 h in K. scombri and 1–5 h in K. sprostonae. No response to light was detected in larvae of G. cochlear. Most older larvae of Kuhnia spp. and of G. cochlear swim continuously upwards and downwards, even in ‘darkness’, indicating an alternation between positive and negative geotropism. The larvae of Kuhnia spp. possess angular cells (?) of unknown function close to the pharynx. The larvae of all three species contain prominent anterior glands and lipid droplets; the latter are depleted during their long free-swimming lives (up to 36 h in Kuhnia spp. at 13–14°C).

The expected allometry between the linear cirral length and animal volume or weight for isometry should be 0·33; similarly the rate of beating, db/dt, might also be expected to increase as −0·33 with volume. The average allometry index of cirral length is less in both Balanus balanoides (0·22–0·23) and in Elminius modestus (0·27–0·32). The segment numbers also rise less than expected.

The rate of beat in Balanus balanoides correlates well with size (-0·28) and with temperature with a correlation coefficient of 0·898, significant for both variables. For a group of 11 species the relation between maximum rate of beating and size over 5 decades gives an approximate allometry of −0·24 which is also less than the expected −0·33 for an isometric linear appendage moving at constant velocity. It is suggested that the approximately reciprocal allometry index between cirral beating rate (−0·28) and cirral length (+0·22) may be mutually compensating, resulting in the cirri moving through the water at a constant rate during the growth of the animal. This rate may maximise the chance of prey being captured.

A further 69 recaptures are reported from a tagging study of pelagic sharks initiated in 1970 in the north-east Atlantic. Galeorhinus galeus tagged in England were recaptured in the eastern Atlantic from southern Spain to north-west of Iceland. Among the 42 G. galeus recaptured the longest time at liberty was about 12 years and the greatest distance travelled was 2461 km. Among the 21 Prionace glauca recaptured the l ongest time at liberty was 10.7 years, and seven sharks moved distances between 4362 and 7176 km. One shark tagged in south-west England was recaptured in the South Atlantic off South America. An Isurus oxyrinchus was at liberty for 4–6 years and a Lamna nasus for up to about 13 years. Lamna nasus were recaptured from northern Norway to northern Spain. The growth rates of the tagged sharks were close to the predicted values for G. galeus, were slower for P. glauca and faster for L. nasus.

The population structure of the thornback ray, Raja clavata L., expressed in terms of length and sex, seems to be related to hydrological conditions prevailing on the sampling areas. In the exposed area (Cove of Bertheaume), females are more frequently captured than males, and indeed represent the entire catch in the summer. In contrast, in the relatively sheltered area (Bay of Douarnenez) a majority of adult males and immature females are caught.

After winter, only adults and juveniles of Raja clavata migrate into the Bay of Douarnenez. This bay may be a mating area for adults and also a nursery for juveniles particularly for immature females.

Samples of Balanus improvisus were collected from 15 sites in the Baltic, the west coast of Sweden, the British Isles and North America. They were analysed with horizontal starch gel electrophoresis for 11 loci and with opercular plate morphometry for 10 metrical characters. Analyses of isozyme patterns revealed a high degree of genetic similarity amongst populations. The Baltic sites, however, showed less heterozygote deficiency than the British and American sites indicating higher stability and outcrossing in the Baltic. Morphometric characters showed somewhat more heterogeneity than isozymes. The Baltic was relatively more homogeneous by morphometrical characters than by isozymes compared with the other areas. Both analyses separated to some extent the three geographical regions from each other and clustered sites by salinity. Individuals at low salinity had relatively small opercular openings compared to individuals from high salinity.

Prior to moulting, the preadult Lepeophtheirus pectoralis produces a temporary frontal filament which attaches the animal to the surface of the host during ecdysis. This filament is extruded from a frontal organ previously thought to have a chemoreceptory function. During ecdysis the exuvium splits at the anterior margin and is shed posteriorly by contractions of the body. After hardening of the exoskeleton the copepod detaches itself from the frontal filament and is free-living on the host during intermoult. Males in precopula position hold on to the dorsal side of the female, with the second antennae grasping the anterior end of the female's genital complex. During the ecdysis of the female, most males release their hold on the female, and are usually found close to her on the host. Copulation occurs between an adult male and an adult female with a hardened exoskeleton. In the copula position the male holds on to the female's genital complex with the second antennae, but now on the ventral side of the female. Two spermatophores are extruded and then transferred simultaneously to the female with the aid of the second pair of swimming legs. Tubes originating from the spermatophores connect them to the orifices of the receptaculum seminis. These tubes seem to grow out of the spermatophores after expulsion. After copulation, the male retains a precopula position before releasing the female. No agonistic behaviour has been observed between a precopulating/copulating male and additional males. However, during the ecdysis of the female, a new male may take over the female, but mating does not seem to be assortative for size in Lepeophtheirus pectoralis.

Unlike other sea turtles, the leatherback Dermochelys coriacea forages widely in temperate waters during summer and dives to abyssal depths (>1000 m) where temperatures are low. There is strong anatomical plus limited physiological evidence in favour of at least facultative endothermy. The lipids of leatherbacks exhibit features which are consistent with maintenance of a core temperature above ambient levels when in cool waters. The lipid of flipper adipose tissue freezes at a lower temperature than lipids extracted from the blubber lining carapace and plastron. Lipid freezing points in leatherbacks are lower than for tropical caimans or terrestrial sheep, but higher than for lipids taken from the blubber of a grey seal. Leatherback adipose tissues show levels of unsaturation in neutral lipid fractions intermediate between those of seals and sheep.

Measurements of fecundity are given for plaice (Pleuronedes platessa L.) sampled from Cardigan Bay. Values were compared with those obtained in 1953 from Cardigan Bay and from the eastern Irish Sea, and no differences were found; a marked contrast to results from the North Sea. Analysis of egg size showed that eggs develop earlier in older fish. A mechanism for ‘fine-tuning’ of fecundity is discussed. Size and age at maturity are calculated for Cardigan Bay plaice, and are compared with rates from surrounding areas. Plaice mature at an earlier age in Cardigan Bay.

Gigantocypris is a good swimmer, capable of moving fast enough to overtake a variety of zooplanktonic Crustacea and chaetognaths. It swims smoothly without violent accelerations and decelerations. Previous reports of unstable weak swimming in this species stem from the study of overheated animals; Gigantocypris is stenothermal, adversely affected at temperatures above about 15°C. Gigantocypris is nearly neutrally buoyant (sinking speed 0·2 mm s−1) and is capable of hovering for long periods with the aid of slight movements of the propulsive antennae. When swimming quickly Gigantocypris achieves an average speed of 164 mm s−1 (9·6 mm body length; 391 antennal beats min−1) at 12·5°C. It is unlikely that Gigantocypris performs significant diurnal vertical migrations. The heart of Gigantocypris is large and beats at ca 100 beats min−1. Macrocypridina is a faster swimmer (<52·3 mm s−1 (8·3 mm body length) at 12·5°C with an antennal frequency of 583 beats s−1), but each beat is accompanied by great accelerations and decelerations. Macrocypridina is dense, sinking at 40 mm s−1. Macrocypridina is eurythermal, its swimming speed increasing steadily between 11·5 and 20°C.

An attempt was made to determine whether bistramide A (=bistratene A), a polycycloether with biological activity isolated from Lissodinum bistratum Sluiter, originates from the ascidian itself or from its symbiont Prochlorophyta. A high-pressure liquid chromatography assay carried out on the whole ascidian, the ascidian without a portion of its Prochloron and the Prochloron themselves gave concentrations respectively of 0.182,0.166 and 0.850%. In view of these results, as well as of the capacity of Prochloron to synthesize complex nitrogenous products and the cytotoxicity of these products, it is hypothesized that bistramide A originates exclusively in Prochloron.

The distribution of intertidal isopods with respect to algal species was investigated over a range of 250 km on the shores of north Spain. A survey of 25 localities included three zones with a distinct composition of algal species: a western zone comprising shores facing Atlantic waters and the outer part of the Bay of Biscay; a narrow transition zone (about 70 km in length); and an eastern zone extending to the inner part of the Bay of Biscay. Thirty two isopod species were collected, 11 of which were present in high densities. Response to geographical change was observed to occur clearly in three species, Ischyromene lacazei, Idotea pelagica and I. baltica, and to a lesser degree in I. granulosa; the former two and the latter two were abundant in the eastern and western zones respectively. All four species were found to be closely associated with macroalgae species which display geographical changes in abundance (e.g. Laminaria ochroleuca and Comllina elongata). In addition, Idotea species were found to inhabit a reduced number of algal species compared with other European shores. Spanish shore of the Bay of Biscay probably constitutes the geographic limit of the distribution of the four species. A sampling artefact might also be responsible to some extent for the patterns of distribution observed. Differences in the physico-chemical properties of sea water along the coast and circulation of coastal waters are not thought to influence the distribution of isopods.

Water samples, taken from station El in the English Channel, were incubated in 12–1 bottles and monitored for nine days. The distribution pattern of photosynthetically incorporated 14C was followed in three different size-fractions (0·2–2 μm, 2–10 μm and >10 μm) during the development of a bloom.

A rapid increase in chlorophyll was observed just after enclosure, the highest values being reached by day 5, when a mixed community of diatoms and small flagellates formed the bulk of phytoplankton biomass. As the bloom developed, nutrients were depleted and, consequently, a decay of the phytoplankton populations occurred. Growth rates, estimated as chlorophyll-specific production rate, were higher for the largest size-fraction (0·53 d−1) than for the intermediate and smallest ones (0·32 d−1 for both).

Throughout the bloom, the proportions of 14C incorporated into protein and low molecular weight metabolites (LMWM) were small, whereas the synthesis of storage products appeared to be enhanced. Carbon fixed into protein was higher during the exponential growth phase in all size-fractions, and incorporation into LMWM increased sharply when the bloom declined. Storage product synthesis varied between size-fractions.

A close relationship was observed between growth rates, estimated as chlorophyll-specific production rate, and the protein/metabolite synthesis ratio (r2=0·90; n=24). These results suggest that, within the range of environmental variation we studied, this ratio would be a good estimator of growth rate for field studies.