Laboratory observations indicate that larvae of Pecten maximus (L.) pass through three phases of swimming behaviour before metamorphosis. Trochophores and early veligers generally swim upwards and, in shallow containers, tend to accumulate at the surface. Their swimming cilia beat without interruption so swimming is continuous. After 3 days of development, pauses in ciliary beating occur intermittently and the veliger becomes capable of withdrawing into its shell. It alternately swims up a vertically orientated spiral and sinks. This type of swimming behaviour is also displayed by the pediveliger, but this larva also periodically swims close to, or crawls on, the substratum. The tendency to accumulate at the surface becomes less pronounced as larvae grow older. By the pediveliger stage it is replaced by an increasing tendency to accumulate close to the substratum.

Limpet populations of the genus Patella from the south-west coast of England were examined by means of gel electrophoresis in order to settle debate on the specific status of the three Patella forms. Populations varied morphologically along an east-west gradient, from three distinct forms in the west to continuous intergradation in the east, in accord with earlier studies. Patella collected were divided into three groups on the basis of a complex of external features described by earlier workers, corresponding to the morphologically defined taxa P. vulgata Linn., 1758, P. aspera Röding, 1798, and P. depressa Pennant, 1777. These groups were electrophoretically distinct in five of seven enzyme systems examined, with no hybrids or intermediates. Incomplete speciation and hybridization can be ruled out as possible causes of the observed morphological variation.

The uptake, transport, storage and excretion of zinc has been studied in Mytilus edulis. Zinc accumulates in the soft tissues in proportion to its concentration in sea water whilst the concentration in the haemolymph is little above that in the environment. Uptake is via the gut, mantle and gills. The zinc is transported from the gills and gut (t½ ≈ 8 days) via the haemolymph, either as a high molecular weight complex or in the granular amoebocytes, to the kidney. Most of the body zinc is present in the granular amoebocytes (which are found in all the body tissues) or in the gut and kidney. The kidney forms the major storage organ for many trace metals, containing 30% of the body zinc and a concentration of about 1000 μg/g. Zinc is localized as insoluble granules in membranelimited vesicles occupying some 20% of the cell volume. Excretion of zinc is by defaecation, exocytosis of the kidney granules into the urine and diapedesis of the amoebocytes. A multicompartmental model for zinc metabolism which correlates the ultrastructural and kinetic data is proposed.

Growth rates in shell height on the shore and the number of eggs released in the laboratory during the spawning season were extremely variable among Littorina neritoides from a population on Anglesey, N. Wales. Much of this variability was attributed to the effects of unpredictable weather conditions on feeding activity. Thirtyper cent of the individually tagged snails in the population did not grow during 1976–8. Growth increments of the remaining snails were used to estimate the growth parameter, k, of the von Bertalanffy growth equation, and the asymptotic size, h∞, used in the equation was estimated to be 7·5 mm, corresponding to the largest individual found in the population. The von Bertalanffy equation was then used to construct a growth schedule for L. neritoides from post-settlement to the attainment of the asymptotic size. From this schedule, snails were expected to take at least 9 months to grow to a shell height of 2 mm and at least 5 years to grow to 7 mm. This growth schedule agrees closely with growth rates observed by Lysaght (1941) in a population at Plymouth, but predicts much lower growth rates than those estimated by Daguzan (1976) for a population in Brittany. Eggs were released from March to June in 1977 and from January to June in 1978. The extreme individual variability in egg production largely obscured the underlying relationship between fecundity and body size. The maximum observed fecundity was for a 71 mm snail which released a total of 3866 eggs during the 1978 spawning season. The average fecundity was 22 eggs per day during the 1978 spawning season, or about 300 eggs per season.

Bivalve larvae constitute an important part of the plankton and there is a pressing need to be able to identify the various species.

The study of the development of the larval and post-larval hinge by scanning electron microscopy of 18 bivalve species shows the importance of this structure, which represents the principal character in identification of the young larval stages. This paper presents the principal distinguishing characters of the hinge (denticles, teeth and ligament) in eight families of bivalves.

L-glutamate is shown to have excitatory effects on muscles of the lamellibranch, Pecten and of several cephalopods. These effects are reversibly blocked by known glutamate antagonists. In Pecten intracellular electrical recording revealed a similarity between the effects of topically applied glutamate and nerve stimulation.

The hydrostatic permeability of the aboral integument of the starfish Asterias rubens L. was found to be 5·1 ± 2·1 × 10−6 cm3/cm2/s/cm H2O. A sudden increase in permeability around 5 cm water pressure was found to coincide with the bursting of the dermal branchiae.

The area of protracted dermal branchiae per cm2 of aboral integument has been estimated and, if only this region represents the permeable areas of the skin, the above figure may well rise to 1 × 10−5 cm3/cm2/s/cm H2O.

The connective tissue layer of the large intestines of Brissopsis and Echinocardium spp. is shown to contain a massive quantity of ferric iron in the form of ferric phosphate. The ferric phosphate is present as a granular extracellular deposit. In large mature specimens of Brissopsis, the weight of iron present may account for almost 30% of the dry weight of large intestinal tissue. The iron deposit appears to be cumulative with age. It is speculated that the deposit is derived from oxidative deposition of a soluble ferrous salt ingested in reducing conditions.

Analyses of the jaws of Nereis virens have shown that various metals are present in detectable quantities; in order of decreasing concentration these are (with ranges (μg/g dry weight) in brackets) – zinc (10130–18360), sodium (1150–2690), magnesium (616–1080), calcium (531–1130), iron (444–1180), manganese (510–952), potassium (270–960) and copper (4–80), with also lead (8·7), cadmium (0·1) and silver (< 0·1). The most concentrated metal, zinc, is not uniformly distributed throughout the jaw, the highest level occurring in the distal tip (45740 μg/g), falling to a much lower level in the basal part (1790 μg/g). The contribution of some jaw metals to the total body burden varies according to body size: in small worms the jaw zinc accounts for over 40% of the total but in large worms it accounts for 30% or less; jaw manganese contributes over 50% of the total in small worms, dropping to about 20% with increasing size. For silver, cadmium, copper, iron and lead the jaws generally contribute less than 1% to the total body burden.

The production of tubes by the serpulid polychaete Mercierella enigmatica is compared with somatic growth and reproduction, and is shown to account for the greatest portion of production energy expenditure.

INTRODUCTION

The tube of a serpulid polychaete consists of two major fractions, a conspicuous calcareous component comprising small crystals of aragonite or calcite, and a more diffuse organic matrix (Hedley, 1956; Neff; 1971). The continuity of the organic matrix was demonstrated by Hedley (1956), who showed that careful decalcifkation failed to disturb the form of the tube of Pomatoceros triqueter (L.).

The serpulid Mercierella enigmatica Fauvel (Ficopomatus enigmaticus cf. ten Hove & Weerdenburg, 1978) secretes a hard, calcareous tube shortly after it settles from the plankton (Rullier, 1955; Vuillemin, 1965). Initially, tube growth is relatively fast, but as the tube increases in length so the rate of growth declines. However, the tube of the adult worm can be as much as 80 mm in length, or more than four times the length of its body.

Gyrodinium aureclum formed an extensive red tide off the south and south-west coasts of Ireland in 1978. Here are presented observations, made off Kinsale, about the biology of the bloom and the nutrient water chemistry associated with the bloom. Comparisons are made with other Gyrodinium red tides which have been recorded in the literature.

Results from the Continuous Plankton Recorder (CPR) Survey have been used to extend the observation by Boalch & Harbour (1977 a) of the occurrence in January 1977 of a diatom Coscinodiscus nobilis (Grunow), new to British waters. Samples have been taken by the CPR to the west of the British Isles since 1948 and along the English Channel since 1957. C. nobilis was not identified until the spring of 1977, thus confirming the observations by Boalch & Harbour. It reappeared in 1978 when it was found further north in the Irish Sea.

The chlorophycean alga, Brachiomonas submarina var. pulsifera Droop, was grown in two bacteria-free chemostats, differing only in the amount of light each received. Investigations were made into the changes in biochemical composition and calorific value of the cells when they were grown at different growth rates. This information was used to help to explain changes in the growth efficiency of the rotifer Brachionus plicatilis Miiller, grown in a bacteria-free chemostat which was linked to one of the algal chemostats, the algae being supplied as the source of food.

In the sprat the utricular receptors are closely associated with the bullae, structures which convert pressures into liquid displacements, and with other structures concerned with detecting vibrating sources. This paper considers morphological features which relate to questions of mechanical coupling between utriculus and bulla, and of the number and orientation of the receptors.

Electrical responses were obtained from the utriculus of the sprat (Sprattus sprattus L). during stimulation by bursts of oscillatory pressures ranging in frequency from 2·5 to 880 Hz and in amplitude from 0·12 to 220 N m−2 (28–93 dB above threshold). These responses had double the frequency of the stimulus and we argue that they were given by two major groups of utricular receptors, one group (decompression or d-receptors) responding to movements of the utricular floor away from the fenestra of the auditory bulla, the other group (compression or c-receptors) responding to movements of the utricular floor towards the fenestra. These groups were identified with oppositely oriented groups of utricular hair cells coupled mechanically by the rigid base on which they lie. Responses grew with increasing stimulus strength over a range of over 100 dB, the slope of the log-log relation decreasing with the larger stimuli. Above 40 Hz the delays between responses and mechanical displacements were very small and the amplitude of response depended only on the amplitude of displacement and not on frequency. Below 40 Hz the sensitivity declined more steeply with reduction of frequency than would be expected from the mechanical responses of the utricular floor. When stimulating frequencies were mixed the responses were not those expected on the hypothesis that different groups of receptors were excited by the different frequencies but those expected if all displacements of the utriculus towards or away from the fenestra from a rest position gave responses in either one or other of two major groups of receptors. The response to mixed frequency pressure waves was such that high peaks were exaggerated and information about polarity preserved. The response of the utriculus to the first cycle of a burst of sinusoidal pressure stimuli was usually larger than that to subsequent cycles.

The use of freeze-branding as a field-marking technique for flatfish is described. Similar recapture rates were obtained for flounders marked on the coloured, or eyed, side and for those marked on the white, or blind, side during the first two years after marking. Brands on adult flounders were still identifiable more than four years after release of the fish. The branding technique is also applicable to plaice.

Montagu's blenny, Coryphoblennius galerita was reared to late larval stage under laboratory conditions. The adult male guarded the eggs and aerated them with its tail during the incubation period. The larvae had a small amount of yolk on hatching and although they appeared to be feeding on the variety of food introduced, no food was observed in the gut. The gas bladder, observable above the gut in all larvae, was filled with gas only in the one specimen, killed at 45 mm T.l., which survived after the yolk was utilized, and in some 4 mm specimens taken from the plankton off Mweenish.

Descriptions are given of the larval stages and of juveniles taken from rock pools.

An occurrence of ‘milky water’ which covered a wide area of the North Sea in June 1975 is described. The water contained 20 mg/1 of an oil which was shown by capillary GC-MS to consist mainly (> 80%) of two wax esters 34:1 and 36:1. Analysis of the acids and alcohols released by hydrolysis, and interpretation of the wax ester mass spectra, indicated that the 34:1 ester was almost entirely composed of the alcohol-acid combination 20:1–14:0 and the 36:1 ester was composed of 22:1–14:0 (75%) and 20:1–16:0 (19%). Wax esters of virtually the same composition predominate in the lipids of the copepod Calanus finmarchicus which has the implication that the ‘milky water’ was caused by ageing of the oil released following a mass mortality of copepods. The lack of polyunsaturated wax esters and of astaxanthin is ascribed to oxidative degradation of these labile lipids following release into the sea. A copepod origin for the milky water is further supported by its containing small amounts of cholesterol and pristane, both of which are common to Calanus species.

Re-examination of the original and subsequent data from Secchi disc studies leads to a revised constant in the light attenuation formula applicable to general field-work.

In theory, the depth at which a Secchi disc disappears from an observer's sight, Ds, is inversely proportional to the sum of attenuation coefficients for diffuse and collimated photopic light (Tyler, 1968). By definition, photopic light is measured by a sensor with the same spectral response curve as the normal human eye. In practice, the usefulness of the theoretical equation is restricted. More commonly, a simple empirically derived formula is used to estimate the attenuation coefficient for diffuse downwelling light, k, directly from Ds. Poole & Atkins (1929), in their pioneering work on light penetration in the sea, derived the relationship k × Ds – 17 for water in the English Channel. This formula is used extensively by workers who are unable to measure k directly and it is given regularly in oceanography and marine biology texts. More recently, a number of investigators have proposed alternative equations relating k to Ds in different regional seas (Table 1). However, Idso & Gilbert (1974) have fitted data of some of these authors, together with measurements of their own, to the original Poole and Atkins formula with good correlation. They suggest that k × Ds = 1.7 is a universal approximation for all natural waters. In view of the continuing importance of the Secchi disc as a measure of underwater light for primary production calculations and other studies, a universal formula is certainly desirable. However, re-examination of the Poole & Atkins measurements has revealed an error in the method of calculation of k.

Talitrus saltator, a supralittoral, sand-beach amphipod, exhibits a nocturnal, circadian, locomotor rhythm entrained by the natural photoperiod (nLD). A phase-response curve (PRC) (light pulse: 2h/400 lx) of the free-running rhythm exhibits a conventional shape; steady-state delay shifts of approximately 3·5 h occur in response to light pulses around subjective dusk, with similar advance shifts when exposed to light pulses around dawn. The seasonal variation of the overt expression of the rhythm indicates that entrainment is predominantly non-parametric, while the constant phase-angle difference between the peak of locomotor activity and dawn confirms the latter as the effective field signal for entrainment. The qualitative relationship between the time scale of the PRC and nLD, together with the absence of any seasonal variation in the periodicity of the free-running rhythm (τ), suggests that entrainment occurs through the interaction of phase shifts defined by the PRC, essentially in response to the systematically changing photoperiod.