Relative abundance, seasonal occurrence, population structure and growth-rate are described for a population of the grey mullet Liza aurata from Langstone Harbour, Hampshire. The occurrence of juveniles as small as 21 mm is interpreted as evidence for spawning in British waters, but no direct information on spawning areas or spawning seasons was obtained.

First reports of the association between Exspina typica and three species of abyssal holothurian are presented. These records suggest that the association is a real one, and not an artefact of sampling, but throw no light on the nature of the association. The geographic and bathymetric distributions of E. typica are summarized, and the species is shown to be a widely distributed cold water stenotherm.

Orientated navigational behaviour in Talitrus saltator (Montagu) was studied throughout the diel cycle. Amphipods released at the centre of a circular arena without an artificial horizon on the periphery showed random escape directions at all times of day. In the presence of an artificial light/dark boundary the escape direction was random at night but was towards the boundary by day. The onset of significantly orientated navigation occurred just before the time of dawn and persisted in a typically circadian manner for 7 days in amphipods kept in continuous darkness.

The phase of the circadian rhythm could be reset in altered light/dark cycles. Phase changes were directly proportional to imposed L:D phases over the range —4 to + 12 h, except that shifts from —2 to +2 h induced no phase change in the orientation rhythm. The endogenous pattern of change of orientated navigation is discussed in relation to the nocturnal endogenous locomotor activity rhythm of Talitrus and its diel pattern of foraging and burrowing behaviour on sandy beaches.

The partitioning and utilization of energy reserves during embryogenesis were followed in the cirripede Balanus balanoides and related to the described sequence of developmental stages. Egg volume and dry weights were measured. Between the recently fertilized egg and eggs containing well-developed embryos at the end of natural incubation there is a doubling of egg volume.

The biochemical composition of the newly fertilized egg is dominated by TCA-insoluble protein (55 %). Neutral lipid accounts for 17 % of the dry weight, while phospholipid and polysaccharide contribute 3–5% and 5–7% respectively. About 36% of the TCA-insoluble protein is utilized during in vivo development, accounting for about three-quarters of the energy expenditure. During this time 40% of the carbohydrate and 20% of the neutral lipid reserves are also utilised. However, when starved adults retain their mature egg masses beyond the normal term, egg metabolism occurs largely at the expense of the remaining lipid reserves. These would be exhausted in a further 6–7 weeks and the embryos unable to survive. The ability of adults to postpone hatching may therefore have important implications for the energy reserves and viability of the newly hatched nauplii. Protein supplies most of the energy during embryogenesis, with neutral lipid assuming increased importance after development has been completed.

Oxygen consumption of the egg masses measured in vitro was converted through aerobic oxycalorific equivalent into biochemical loss. This showed good agreement with direct measurement of summed energy losses of the biochemical components. It was apparent that oxygen uptake rate in the later stages was restricted by diffusion resistance due to egg packing, since eggs freed from the egg mass matrix showed a 30% increase in oxygen uptake and a reduction in development time.

The feeding successes of four species of crabs (Crustacea: Brachyura) which are potential predators of the scallop Pecten maximus (L.) were studied under laboratory conditions. When provided with scallops of 4 and 5 cm shell height, Liocarcinus depurator (L.) did not consume any scallops whereas Liocarcinus puber (L.), Carcinus maenas (L.) and Cancer pagurus L. ate both size groupings but with varying success. The differences in the number of scallops eaten paralleled crab size such that C. pagurus, the species with the largest individuals (ca. 10.4 cm carapace width), ate the most, and small crabs (< 5.5 cm carapace width), irrespective of species, ate none or very few scallops. Further experiments with C. pagurus and a wider size range of scallops (3–9 cm shell height) revealed the following trends: as prey size increased, the proportion of crabs feeding decreased and there was minimal predation on scallops > 7 cm shell height; male and female crabs showed similar predatory behaviour; and marine fouling on scallop shells had no significant effect on crab feeding (X2 test, P > 0.05). These findings are discussed in relation to the potential for bottom culture of P. maximus.

The correlation between settlement rate, cypris age and anatomical maturation on the ultrastructural level was studied in female cyprids of Lernaeodiscus porcellanae, a rhizocephalan parasite of the porcelain crab Petrolisthes cabrilloi. There is no settlement on crabs until the cyprids are at least 2–3 days old, and maximum settlement activity is only reached 5 days after the moult from nauplius to cyprid (at 15 °C). Thereafter the settlement rate decreases again, possibly due to depletion of energy reserves in the non-feeding cyprids. Ultrastructural investigations show that the female cyprids cannot metamorphose into a kentrogon until 2–3 days after the moult from nauplius to cyprid, which explains the absence of settlement in young cyprids. Competence to metamorphose depends on changes in the cement glands, the epidermis and the antennules. The cypris moult cycle is arrested at an early stage and moult activity is only resumed after settlement. This ensures that the cyprids will not initiate metamorphosis while free-swimming.

It has been shown that the early development of the monogenean Calicotyle kröyeri takes place in the rectal gland of its hosts (various species of Raja). Adult parasites were found in the rectal gland as well as in the cloaca. The invasion route followed to the rectal gland remains unknown, in spite of a search for post-larvae in scrapings from the cloacal lining, rectal lining and ventral skin near the cloacal opening and in blood vessels leading to and from the rectal gland. The growth of the hamuli is described.

The cheliped stridulatory structures are described for Trizopagurus strigimanus, T. melitai, T. tenebrarum and T. strigatus.

Sound in T. strigimanus is produced during reciprocal flexion and extension of the carpo-propodite and mero-carpopodite joints of tightly apposed chelae. These underwater sounds occur as syllables, each of which is composed of damped pulses with a repetition rate of 36–303/s and a within-pulse frequency of 6–8 kHz. The maximum sound pressure level (peak to peak) 15 cm from the source was 24 dB re: 1 Pa.

The gastropod shells inhabited by T. strigimanus had a weak effect (5% pressure difference) on directional radiation of sound in the near field (5 cm) and no effect beyond 20 cm from the crabs.

Cavity resonance of the shells was predicted from a mathematical model, but only appeared important at a fundamental frequency of about 4 kHz, when tested in animals partially removed from their shells. A more significant effect was low-frequency vibration (100–300 Hz) imparted to the shells through direct contact by the hermit crab inhabitants.

Behavioural experiments suggested that the function of T. strigimanus stridulation is defensive, particularly against conspecific aggressors. This may reduce intraspecific competition for shells in Trizopagurus.

The effect of β-alanine on the concentration of taurine and other free amino acids (FAA) in different osmotic conditions in Mytilus galloprovincialis have been investigated. Significant variation of the concentration of FAA as a function of the salinity have been observed.

β-alanine incorporation decreases the level of cysteic acid and taurine as well as the level of other FAA.

Two berycomorph fishes, Hoplostethus atlanticus and H. mediterraneus, were captured by bottom trawls on the continental slopes to the west of the British Isles. H. atlanticus was seldom abundant and was distributed at a depth of about 1250 m both in the Rockall Trough and the Porcupine Sea Bight. H. mediterraneus was only present in the Porcupine Sea Bight and was moderately abundant at depths of about 750 m. Few juveniles of either species were captured and there was no evidence to suggest that H. atlanticus spawned in the area. Seasonal changes in the gonosomatic index of H. mediterraneus indicate that spawning occurs in the autumn and that the environmental conditions at this northern limit of its distribution may be unsuitable for larval or juvenile survival. Juvenile H. mediterraneus were relatively abundant in bottom trawls off West Africa. The diets of both species were broadly similar in that they preyed primarily on benthopelagic organisms, especially mysids, decapods, fish and cephalopods.

The clupeid fishes Clupea harengus and Sprattus sprattus have small cellular tags projecting from the surface of the epidermis of the head and the margins of the scales. The tags are innervated and assumed to be tactile sensory organs. The fine structure has been investigated by scanning and transmission electron microscopy. The protruding part consists of a core of four columns of cells joined by numerous desmosomes, less firmly attached to a single layer of superficial cells. Fine, varicose, nerve fibres run under the superficial cells and end freely. Beneath the tag is a group of prominent basal layer cells and a dermal intrusion with a small nerve. No Merkel cells have been detected in the organs.

The geographical distributions and seasonal cycles of pelagic larvae and post-larval stages of decapod Crustacea in the north-eastern Atlantic and the North Sea during 1981–3 are described from samples taken with the Continuous Plankton Recorder (CPR). Analyses of the distributions of 36 common taxa identified groupings which could be related to depth and temperature. The seasonal occurrences of planktonic larvae of benthic taxa were found to be correlated with sea-bottom temperature in the winter as well as parameters of the sea-surface temperature. Possible interpretations of these data are discussed.

Pelagic eggs and demersal eggs of teleosts both have osmotic concentrations similar to that of the maternal body fluids, less than half that of sea water. Pelagic eggs are buoyant because they contain such large quantities of this dilute aqueous fluid. While the demersal eggs of teleosts usually have a water content of 60–70%, the buoyant pelagic eggs of marine teleosts such as whiting, Norway pout, saithe, cod, haddock, turbot, dab, plaice, witch, long rough dab, halibut and sole typically have a very high water content (ca. 92 %) and a lipid content of 10–17% of egg dry weight. About 90% of the buoyancy of such eggs in sea water is caused by their high aqueous content, only about 10% being caused by lipid. The buoyant eggs of grenadier and ling have large oil globules and higher lipid contents, 27 and 35 % of dry weight respectively. Nevertheless, most of their buoyancy is provided by their high aqueous contents (89 and 81 % water). The high water content of pelagic eggs is brought about by a massive influx of water into the oocytes during meiotic maturation (ripening) after vitellogenesis but before ovulation. In cod and plaice, ripening is accompanied by a four- to five-fold increase in both water content and free amino-acids, and by a large influx of both potassium and sodium. In cod, free amino-acids contribute much more than these inorganic ions to the water influx and to the total osmotic concentration of the mature egg, but in plaice the relative contribution of inorganic ions approaches that of the free amino-acids.

Tagging data for 5959 bass, Dicentrarchus labrax L., released around England and Wales between 1970 and 1984 have been compiled and analysed to show seasonal distribution patterns and implied movements of populations in the southern North Sea, the central English Channel and the south-west and west coasts. Juvenile bass appear to remain near their nursery areas throughout the year, whilst adults show extensive migrations between summer feeding areas and winter pre-spawning areas, which are specific to local populations. Straying occasionally occurs between populations, but only at the ‘adolescent’ phase, and for management purposes local populations may be considered discrete.

Haemoglobin is present, often at high concentration, dissolved in the blood of all small Pogonophora so far examined.

The haemoblobin of Siboglinum fiordicum resembles annelid and vestimentiferan haemoglobins in having subunits with molecular weights of 15000–16700 plus traces of 35000–40000 MW material. 5. fiordicum haemoglobin has 1 mol haem per 21500 g protein, and a similar lack of correspondence between subunits and mols of haem is shown by annelid and vestimentiferan haemoglobins. However, S. fiordicum haemoglobin differs considerably from annelid and vestimentiferan haemoglobins in other respects, even though the three groups are closely linked taxonomically. The haemoglobin of S. fiordicum has a lower apparent molecular weight (Mr = 3.5–4.0 x 105) than that of annelid haemoglobins (Mr = 3–4 x 108) when measured under the same conditions. Pogonophore blood examined with the electron microscope does not show the two-tiered hexagonal structure found in annelid and vestimentiferan haemoglobins. S. fiordicum haemoglobin also differs from annelid and vestimentiferan haemoglobins in amino acid composition.

The haemoglobins of the small pogonophores examined have a very high affinity for oxygen. The P 50 ranges from 0.36 Torr in diluted blood of S. fiordicum (15 °C) to 0.5–1.0 Torr in undiluted blood of S. atlanticum (10 °C) and s. fiordicum (15 °C). Only a slight Bohr effect was found. The high oxygen affinity can be related to the wide range of P o2 values experienced in the habitat and the need to transport oxygen to the deeply buried posterior end of the body that contains autotrophic endosymbiotic bacteria.