The climbing behaviour of the gastropod Hydrobia ulvae (Pennant) and its relationship with flotation/dispersal were investigated by field observations and experiments in Norfolk, U.K. and by laboratory experiments. Field experiments of the type used by previous authors were discontinued when it was observed that counts at low tide of snails which had climbed objects the previous high tide did not reflect adequately climbing activity during that period of tidal cover. Both field and laboratory studies yielded five general results: (i) snails climbed only when covered by tidal water; (ii) climbing activity was not related to population density; (iii) climbing activity, under conditions of constant population density, varied markedly during the cycle of spring tidal cover, reaching a peak after the first few tides and declining rapidly thereafter; (iv) maximum numbers of snails were present on submerged structures relatively early in any given period of cover and declined (snails crawled downwards off the structure) as the period of cover continued; and (v) rarely were large proportions of climbed Hydrobia floated off their support by the incoming tide; this was associated only with conditions of extreme calm.

In a series of laboratory experiments designed to create conditions under which the dispersal and feeding hypotheses of climbing in Hydrobia ulvae would predict opposing results, significantly larger numbers of snails climbed (a) food-bearing sticks than non-food-bearing sticks, (b) in 100% sea water than in 41% sea water, and (c) in the dark than in the light. The first two of these results are in accordance with the hypothesis that climbing is not a distinct behavioural activity but is merely normal crawling/browsing behaviour carried out in a vertical plane; they are in disagreement with the hypothesis that climbing is undertaken in order to facilitate dispersal away from unfavourable conditions. The third result is neutral in respect of the two hypotheses, but is explicable in terms that activity during the night is advantageous because of lowered rates of vertebrate predation.

Large numbers of Micromesistius poutassou were caught in the English Channel during the spring of 1979. Later in 1979 and in the early months of 1980 smaller numbers were recorded from the southern North Sea where this species has rarely been recorded before. The M. poutassou were accompanied by small numbers of T. esmarkii in the eastern English Channel but no T. esmarkii were found in the southern North Sea. T. esmarkii were taken off Plymouth on two occasions in 1977 and more regularly since 1979. M. poutassou has been recorded there sporadically since 1957. Both species were caught in considerable numbers around the Scillies in 1977 and 1978. The invasion of the English Channel by M. poutassou in 1979 may have come from the Bay of Biscay rather than the Celtic Sea, but the appearance of T. esmarkii in the Plymouth area since 1977 may be a result of changes in the ecosystem since 1964.

Herring larvae, when they are about 30 mm long, swallow air and fill their auditory bullae with gas. It has been shown earlier that this is associated with a great increase in sensitivity to changes in hydrostatic pressure. Here we show that it is also associated with the appearance of a startle response to noises.

At this stage of development, the utricular maculae are fully developed. However, the bullae are bounded by thin walls which are poorly calcified and the bulla membranes are thin and contain little elastic tissue. None the less the high-frequency cut-off in the mechanical responses to oscillating pressures is as high as that of the adult.

The mantles of the small squid Alloteuthis, the larger Loligo, and the cuttlefish Sepia contain an elaborate framework of connective tissue fibres running in different planes. Some of these fibres are apparently elastic. The circular muscle fibres which provide the power stroke in mantle contraction are of two types. Inner and outer mantle zones consist of well-vascularized mitochondria-rich fibres, whereas the central zone contains only mitochondria-poor fibres with a sparse vascular bed. Nerve terminals on the two fibre types are similar. The radial fibres opposing the circular fibres are of the same type as the central fibres, at least in the mid-region of the mantle. It is suggested that the central fibres are involved in escape jetting contractions, and that the fibres of the inner and outer zones are used during rhythmical respiratory contractions.

The distribution, abundance and seasonal occurrence of larvae of mackerel (Scomber scombrus L.) are described from routine Continuous Plankton Recorder (CPR) sampling around the British Isles over the period 1948–78, and from more intensive CPR sampling in the Celtic Sea in 1977. There were two main areas of larval concentration: in the North Sea and over and adjacent to the Celtic Plateau; subsidiary aggregations were observed to the northwest of Ireland and to the west of Norway. There were some similarities between the distribution of larvae around the British Isles and that of adult Calanus spp. In the North Sea there was a southerly shift of larval distribution over the period 1948–77; over a similar period the abundance of larvae increased to reach high numbers by the late 1950s and subsequently declined after the mid-6os. To the south-west of the British Isles numbers of larvae showed a long-term decline. The long-term trends of distribution and abundance are discussed in relation to concurrent biological and environmental change. The clearest relationship was found between the numbers of mackerel larvae in the North Sea and sea-surface temperature in the North Atlantic, which suggests a common causative agent for both sets of observations; also, there was a weak relationship with both spawning stock biomass and sea-surface temperature at the spawning areas. In the North Sea the seasonal occurrence of larvae was from May to August, the majority being taken in June and July; over the period 1948–77 the seasonal time of occurrence of highest numbers of larvae has remained relatively constant. In the Celtic Sea the seasonal occurrence of larvae was spread over a longer period, from March to August, with relatively high numbers from March to June; over the period 1950–78 the time of occurrence has been variable, possibly with a tendency towards later timing in more recent years.

There are three species of chthamalids in Europe. Two of them, Chthamalus stellatus and Chthamalus montagui, overlap extensively in geographic range: they occur together along the whole Atlantic coasts of Britain, Ireland, France, Spain and N. Africa, and both also occur in the Mediterranean Sea. They have almost identical north-eastern limits to their distribution in the English Channel and N. Scotland, but C. stellatus may extend farther south along the W. African coast. These two species also show overlap in their vertical distribution, though C. montagui is usually commoner in the upper barnacle zone while C. stellatus may be dominant lower down. The species are separated by habitat, C. stellatus favouring wave-beaten open coast sites, C. montagui more embayed situations, but there is still extensive overlap. The third European species of chthamalid, Euraphia depressa, has a more restricted vertical distribution and is almost entirely confined to the Mediterranean Sea, where it favours high-intertidal levels in wave-beaten places, and also cryptic habitats.

The rate of excretion of ammonia by Nassarius decreases progressively during starvation. Both Nassarius and Buccinum exhibit a transient peak of ammonia excretion some 16–48 h after a meal. In Nassarius the length of the delay between feeding and maximum ammonia excretion depends on the duration of prior starvation.

In an experimental study the cyclopoid copepod Corycaeus anglicus Lubbock was found to ingest Artemia nauplii at much higher rates (up to 15 times) in the light than in the dark. Maximal ingestion rates observed in the light represent daily rations of 70% and 66% of the body carbon for males and females respectively. From experimental observations together with studies of the ultrastructure of the photoreceptors it is suggested that Corycaeus can locate prey visually. This is in contrast to the majority of other copepods which use chemoreceptors and mechanoreceptors.

Laboratory observations on the formation of concentric growth ridges on the shell of small Pecten maximus revealed that their rate of production was related to the size of the shell and to the growth increment in a given period. These factors are related, naturally, and the larger the shell, the greater is the growth increment and the number of ridges produced in a given time. Also, in shells of a similar size the higher the growth rate, the larger is the width of each ridge and the greater is the number of ridges produced. Faster growth is achieved therefore by increasing the width and number of ridges. The rate of ridge production at 10 °C was less than half that at 14·5 °C in conditions which were otherwise identical.

The structure of the anal sacs of the echiuran Bonellia viridis Rolando was studied using SEM, TEM and light microscopy. The characteristic ciliated funnels which open into the coelom and connect it to the lumen of the sac were observed live by interference contrast light microscopy. Clearance of the extracellular marker inulin from the coelomic fluid (Vc = 9·6 ± 1·9 ml 100 g−1 wet weight of animal day−1) indicated that a filtrate of coelomic fluid is produced by the ciliary activity of the funnels. The flow of this filtrate into the sacs is unidirectional. Comparison of the ionic composition and osmolality of the anal sac fluid with the coelomic fluid, and surrounding sea water, indicates that the filtrate passes unmodified by absorptive or secretory processes to the outside. Thus the sacs do not appear to have a clear iono- or osmoregulatory function. During osmotic uptake of water in low salinities the rate of clearance of inulin by the anal sacs did not increase, indicating that their role in volume regulation is insignificant. The reddish-brown granules in the epithelium and lumen of the organ (which give the sacs their characteristic colour) may be important excretory products, and the primary function of the sacs their elimination.

Crassostrea gigas spat were fed diets of Pavlova lutheri, Dunaliella tertiolecta or Tetraselmis suecica. The D. tertiolecta diet contained no fatty acid longer or more unsaturated than linolenic acid (18:3ω3) and the T. suecica diet was deficient in decosahexaenoic acid (22:6ω3). The algal diets were supplemented with micro-encapsulated triolein, oyster lipid extract or 22:6ω3. Spat were also starved or fed carbohydrate diets.

The tendency under field conditions for settling Balanus balanoides larvae to space out from conspecific adults but not from adults of other species is reaffirmed. Explanations are advanced for the opposite conclusions reached recently by other workers. The general avoidance by B. balanoides larvae of settling on top of older barnacles is examined. It is suggested that there must be a strong inhibiting influence, so far unexplained.

The hepatosomatic indices (HSI) of eight groups of Myxine glutinosa with different gonadal conditions are calculated and compared with each other. Female animals with eggs longer than 10 mm differ statistically significant in their HSI from all other groups. The production of a vitellogenetic protein in the liver of Myxine is concluded.

The thin band between growth increments in the shell of Cerastoderma edule is laid down at the end of the period of emersion, when the pH of the mantle and extrapallial fluids are at a minimum of pH 7·0 and 7·2 respectively. The growth increment is formed during immersion when the pH of the extrapallial fluid is 7·5–7·7 and the mantle 7·6–7·8, which is close to that of sea water (pH 7·8).

Nutrient-limited batch cultures of two marine phytoplankton have been subjected to aeration and varying rates of mechanical agitation and the effects of growth and uptake of 14C and nutrients recorded. In both phosphate- and nitrate-limited cultures the lag period decreased with increasing agitation rate. Cell division times in the exponential phase decreased with increasing agitation of phosphate-limited cultures but increased in comparable nitrate-limited cultures. Division times were increased in all aerated cultures. The final yield of phosphorus-limited cultures was greatest at the highest agitation.

A model has been used to assess the relative importance of the various factors contributing to changes in the salinity of the eastern English Channel between 1948 and 1973. As part of the data input to the model, monthly means (1948–73) of total runoff into the eastern English Channel and monthly estimates of evaporation and precipitation for the same area (1961–73) were calculated. The results of this study have shown that river runoff is an important factor contributing to the variability of salinity in the eastern English Channel; rainfall over and evaporation from the Channel may also be important at certain times. The model can predict satisfactorily more than 80% of the variation of salinity from local data inputs. While Atlantic water movements and salinities may contribute to variability at the entrance to the English Channel, variations of flow through the Channel, caused by local wind forcing or originating further out in the Atlantic, have little effect on the fluctuations of salinity in the eastern English Channel. Furthermore, fluctuations in the salinity of the North Atlantic do not correspond to those observed at the entrance to the English Channel. River runoff and mixing due to the wind and tides appear to be the main factors responsible for the seasonal changes of salinity in the eastern English Channel.

The lipids of four marine coccolithophorids (class Haptophyceae), Emiliania huxleyi, Hymenomonas carterae, Isochrysis galbana and Crystallolithus hyalinus, were examined by capillary gas chromatography-mass spectrometry. Fatty acids ranged from C14 to C22 and were predominantly of even chain length. The major acids were polyunsaturated C18 acids, 22:6 and either 14:0 or 16:0. C20 fatty acids were of low abundance. Significant amounts of octadecapentaenoic acid (18:5), previously thought to be unique to dinoflagellates, were identified in three of the algae. A small amount of a di-unsaturated C36 w-alkenoic acid was identified in E. huxleyi, which is the first report of such a long-chain fatty acid in any alga. Traces of wax esters, which are reportedly uncommon inalgae, were found in three of the species. The sterol distributions were very simple, with two or three compounds accounting for > 99% of the total sterols. In each case, the major component was 24-methylcholesta-5,22E-dien-3β-ol. H. carterae and C. hyalinus also contained 24-ethylcholesta-5,22E-dien-3β-ol and significant amounts of cholest-5-en-3β-ol were found in E. huxleyi and I. galbana. An unusual sterol, 23,24-dimethylcholesta-5,22E-dien-3β-ol, was identified in H. carterae. These sterols were mostly non-esterified although small amounts of sterol esters were identified in E. huxleyi. The lipid composition of E. huxleyi is distinctive in that it contains, in addition to the C36 fatty acid, novel C37–C39 unsaturated ketones and C31–C38 alkenes. Of the other coccolithophorids only I. galbana contained small quantities of one of the C3l alkenes.

The paired excretory organs or maxillary glands of the adult barnacles, Balanus balanoides and Balanus hameri, lie within the posterior part of the body below and to either side of the foregut. Each organ has an end sac linked to an efferent duct via a valve. The sac-shaped efferent duct connects with a relatively short terminal duct, opening out at the base of the second maxilla. The end sac consists of podocytelike cells having marked morphological and cytochemical similarities to the equivalent region of other Crustacea and to the vertebrate glomerulus. The main cells of the valve contain extensive apical secretion. They rest upon a series of modified end-sac cells projecting into the efferent duct. The efferent duct is composed of a uniform flattened epithelium which is cytochemically unreactive. The cells are lined by a short microvillous border, below which is a series of tubules which appear to be invaginations of the apical membrane. The morphology of efferent duct cells is not indicative of a highly active solute reabsorptive epithelium, but secretion of membrane-bound bodies into the efferent duct lumen was observed. The terminal duct is a relatively short, cuticle-lined ectodermal infolding. The parenchyma cells surrounding the efferent duct exhibit a marked affinity for certain dyes when injected into the haemolymph, indicative of a possible role in the elimination of material. The excretory organ is surrounded by a network of elastic fibres and is suspended within the body by strands of connective tissue and a complex series of tendon-muscle connexions. The end sac is well supplied with haemolymph from the scutal sinus but the supply to the efferent duct is more restricted.