The occurrence of genetic differentiation among western Mediterranean Hediste diversicolor (Polychaeta: Nereididae) populations was assessed by allozyme electrophoresis on cellulose acetate. Seventeen loci were analysed in four populations. The level of the genetic variability was markedly low (mean HL range: 0.014–0.034), but comparable to that of other brackish water nereidids. The values of Nei genetic distance index (D) confirm the existence of genetic differentiation between the geographically isolated populations at Venice, Elba, Navicelli and Serchio D range: 0.128–0.356). However, the two samples from Serchio and Navicelli, ~15 km apart, were not genetically different (D=0·00005). The level of genetic differentiation in H. diversicolor populations followed the isolation-by-distance model. Reduced gene flow among H. diversicolor populations may be explained by its limited dispersal capacity and the eco-physiological barriers that occur between different brackish habitats.

Samples of Ostrea edulis were collected during 1999 and 2000 from five sites in Scotland, and from one site each in Northern Ireland, Ireland, France, The Netherlands and Norway. Samples were scored at four microsatellite loci. Mean numbers of alleles per locus varied from 12·6 to 16·6 and observed heterozygosity per locus ranged from 0·801 to 0·845. Samples derived originally from hatchery seed showed significantly fewer alleles per locus and significantly reduced expected heterozygosity compared with wild populations. However, observed heterozygosity did not differ significantly between the two groups. Significant deficiencies of heterozygotes were present at one or more loci in four of the ten populations sampled and a significant excess of heterozygotes was present at one locus in a hatchery-sourced Scottish population. Genetic distance indices revealed that the Norway population was the most distinct from all others and that hatchery-sourced populations were also relatively distinct from other wild populations. However, genetic subdivision was generally low implying high historical ‘migration’ rates for these populations.

Habitat preference and spatial distribution of Guiana dolphins (Sotalia guianensis) in Norte Bay, southern Brazil, was studied from 2001 to 2005. Boat surveys (N = 91) were made to evaluate the spatial distribution of the dolphins. Seven habitat variables were integrated into a geographical information system, and habitat preference was tested using the ‘Neu method’ and a habitat index. The Guiana dolphins did not use all habitat types in the same proportion as were available. Areas used more intensively included, in order of importance: (1) areas with a steep sloping sea-floor; (2) areas further from urban areas; (3) areas further from mangroves; (4) areas near the mouth of the bay; (5) shallow water areas; (6) areas of clayey-silt sediments; and (7) areas close to shore. From 2001 to 2005 there was a shift in spatial distribution and habitat use by the dolphins. The low frequency of use of areas close to urban encroachment and its related impacts to the marine environment raises concern about the coastal habitat destruction. The Guiana dolphin may be considered a habitat specialist, despite its wide latitudinal distribution in the western Atlantic Ocean. The ecological niche of the species may be defined by a narrow strip of shallow coastal waters (mostly < 30 m) bordering the coastline. The shift in the spatial use was probably linked with changes in the abundance of important prey of the species and possibly was caused by the collapse of a fish stock in the study area region. Different habitats may favour different assemblages of prey and consequently different foraging strategies by the dolphins. Human-related habitat alterations throughout the range of this species are likely to affect dolphins' ecology in many ways and, thus, must be evaluated and mitigated to conserve their critical habitats.

INTRODUCTION

The family Palmariaceae Guiry (Palmariales: Rhodophyta) at present includes the genera Palmaria Stackhouse (the holotype genus: see Guiry, 1974, p. 523), Halosacdon Kiitzing, Leptosarca A. & E. S. Gepp and Neohalosacdocolax I. K. Lee & Kurogi. Halosacdon and Leptosarca were included in the original description of the family (Guiry, 1974) and Neohalosacdocolax was recently described by Lee & Kurogi (1978) for a small parasite on Halosacdon minjaii I. K. Lee from the Aleutian Islands. The structure and reproduction of Neohalosacdocolax make it quite clear that its affinities lie with the Palmariaceae (Lee & Kurogi, 1978). The Palmariaceae of the island of Hokkaido (northern Japan) have been the subject of a recent study (Lee, 1978) and the details of structure and reproduction given for the northwestern Pacific species of Palmaria and Halosacdon confirm that the unusual structure and mode of reproduction described by Guiry (1974, 1975, 1978) for Atlantic and northeastern Pacific representatives of these genera are also found in the northwestern Pacific representatives (see also Lee, 1977a).

Larvae of the hydrothermal vent barnacle Neoverruca sp. were reared under laboratory conditions and larval development was observed. Under these conditions, the larvae were released from adults as first-stage nauplii, although the larvae of other deep-sea barnacles have generally been considered to be released at a later larval stage such as the cyprid stage. The larvae of Neoverruca sp. were lecithotrophic through six naupliar stages and the subsequent cyprid stage. The larval period of Neoverruca sp. was more than 96 days under the present rearing conditions, which is the longest yet reported for barnacles. Most cyprid larvae, however, exhibited abnormal morphology and no larvae settled successfully on the substrate. These observations suggest that such a long larval period might enable neoverrucid barnacles to disperse between vent fields.

The distribution of Neomysis integer (Crustacea: Mysidacea) in a tidally mixed estuary was found to be concentrated in mid-estuary with animals extending, primarily in summer, further up and down estuary. Within this range there were distinct intra-specific differences in distribution, with males occurring more commonly down-estuary and ovigerous females and juveniles up-estuary. Examination of tidal abundances in mid-channel showed males to be more abundant on the ebb tide, corresponding with their more downstream distribution, and all other individuals to be present mainly on flood tides, which would maintain the species within the estuary. Endogenous circa-tidal swimming activity in this species was found to be phased after the time of expected high tide, which would suggest ebb tide swimming in the estuary. More detailed examination of the distribution of Neomysis across the width of the estuary showed greatest concentrations of animals in slow-flowing water at the edge of the channel during the ebb tide. The endogenous swimming rhythm may therefore act to prevent stranding of animals intertidally during the ebb tide, while maintenance of position along the estuary appears to be by flood tide swimming under exogenous control.

An investigation has been made of the occurrence of 25 amino acids in the hydrolysates of five species of diatoms which had been grown in Erd-Schreiber medium. Their distribution pattern in general resembles that found in other species. However, there are characteristic differences; thus, they contain more serine and 2-amino iso-butyric acid than the other species of phytoplankton.

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 velocity of sound through spermaceti oil from the melon of two Kogia sima specimens, stranded in Florida in 1995, was determined across a range of temperatures between 7 and 38°C and at pressures between 0 and 90 atm. Sound velocity values ranged between 1395-1669 m s−1, increasing linearly with increasing pressure but decreasing non-linearly with increasing temperature. Polynomials were generated to describe sound velocity as a function of temperature and pressure for the core and peripheral lipids of the melon. The results suggest that, at normal body temperature, sound travelling from the back to the front of the melon would have a tendency to focus during dives to any depth, largely due to heat exchange across the periphery of the melon. Effects of changes in ambient temperature and pressure are described and discussed in relation to anatomy.

The reproductive biology of the king weakfish, Macrodon ancylodon, inhabiting the estuarine waters of the Río de la Plata (Argentina–Uruguay), was studied using macroscopic and histological analysis of the gonads. The samples were collected from commercial landings and from three research cruises carried out between 1999 and 2001. King weakfish is a multiple spawner with indeterminate annual fecundity. Spawning of this species extends from October to March with two main peaks of gonadal index in November and March. Based on the incidence of females with new postovulatory follicles, the evening near sunset was the estimated time of spawning for M. ancylodon. Spawning frequency, determined using the percentages of females with postovulatory follicles, was about 17% during March 2001, indicating that females spawn once every six days at the second peak of the reproductive season. Batch fecundity ranges from 12,400 to 225,700 hydrated oocytes and was fitted to a linear function of total length and ovary-free female weight. The number of hydrated oocytes decreased at the end of the spawning season. In addition, a decline in hydrated oocyte size and weight was also observed during this period.

The anatomy of the eyes of several species of mesopelagic decapods (family Oplophoridae), obtained from the eastern north Atlantic, is described and related to the unique light environment of the deep seas. The oplophorid eyes are of the reflecting superposition type, but they show a number of regional morphological variations. The main rhabdom, formed by retinula cells Rl to R7, comes in a variety of shapes, from fusiform rhabdoms in the dorsal region of the eyes of Oplophorus spinosus to multi-lobed interdigitating rhabdoms in deepwater species. The distal rhabdom, contributed to each ommatidium by retinula cell R8, gradually increases in size towards the ventral part of the eye in Systellaspis debilis and O. spinosus. Histological examination of the tapetum shows that it is incomplete dorsally in some species from the upper mesopelagic zone (S. debilis, O. spinosus), and that the amount of reflecting pigment in the tapetal cells increases in the ventral part of the eye. The tapetum is complete in some deep-water species (Systellaspis cristata, Acanthephyra kingsleyi, A. pelagica). These adaptations of the rhabdoms and tapeta are thought to be concerned with increased sensitivity to the dim up-welling irradiance and to bioluminescence. A dorsal accessory compound eye consisting of a small group of apparently functional apposition-type ommatidia is described.

During the summer of 1935 Captain Nicholson of Saltash kindly put his motor-boat at my disposal and took me for seven full-day collecting trips on the estuaries of the Tamar and its confluents, the Tavy and Lynher. I also made some collections from land in the estuaries of the Plym and Exe (S. Devon), Taw (N. Devon), Camel (N. Cornwall), and Towy (S. Wales).

All collecting was done intertidally or in shallow water and was practically confined to the brackish-water reaches. No gear was used except a hand-net of stramin, and a zinc sieve of 1-mm. mesh. More attention was paid to the Crustacean orders Tanaidacea, Isopoda, and Amphipoda than to the rest of the fauna, observations on which were only occasionally made.

Describing the migrations and movements of the cod, Gadus callarias L., in the Barents Sea, Trout (1957) suggested that the immature fish carry out a false spawning migration. ‘The pattern of migration of the immatures is basically similar to that of the matures…with increasing age, the immatures’ southerly winter migration approached in length that of the mature cod, as if, in the years immediately prior to maturity they were making a “dummy run” towards the spawning ground.' The seasonal migrations of both the adult and immature cod have been related to changes in the activity of the thyroid gland in this fish (Woodhead, 1959). During the spring of 1956 and 1957, collections of thyroid glands from immature cod were made at stations from Bear Island to the Norwegian coast. It was hoped that a study of these glands might demonstrate further the relationship of the activity of the thyroid gland to the migration of the fish.

The composition and spatial distribution of the polychaete fauna on the subtidal soft sediments of the Ría de Aldán (Galicia, north-western Spain) were studied by means of quantitative sampling and multivariate analysis. The faunal distribution was mainly conditioned by a sediment gradient defined by decreasing grain size, from the mouth towards the inner margins of the ría. The coarse and medium sand fauna was mainly dominated by pisionids, spionids and syllids. Finer sediments (fine sand to mud) showed a greater abundance of paraonids, spionids and cirratulids and deposit feeding species. The greatest number of species and diversity were found in coarse sediments.

A method of representing the mixing of water in an estuary is given, and the amount of mixing which occurs in the Thames Estuary is calculated. Changes in salinity predicted from the results are found to agree with observation. The application of this theory of mixing to some pollution problems is briefly considered.

During a short stay at the Marine Biological Association Laboratory Plymouth (mid-September 1982) preliminary investigations of the interstitial fauna of marine sand were carried out. The sampling sites with the recorded Mollusca have already been communicated (Salvini-Plawen, 1984).

As concerns mesopsammic Cnidaria, only a few findings have been made in British waters (Boaden, 1963, 1966; Harris, 1972). The present contribution reports not only new records for the Plymouth area and British waters in general, but also provides comparative knowledge of mesopsammic faunas.

The assemblage and the temporal changes of benthic macrofauna inhabiting the Phyllochaetopterus socialis (Polychaeta: Chaetopteridae) aggregates were analysed during 2004 and May 2005 in the Mar del Plata harbour, Buenos Aires (Argentina). Species composition, abundance, richness and diversity were estimated from monthly or bimonthly samples obtained by SCUBA diving. Multivariate (MDS) and SIMPER analyses were applied to analyse the structure of benthic communities. In the mats, a total of 57 species (invertebrates and chordates) belonging to 11 phyla were associated to P. socialis: crustaceans and molluscs were the most abundant species and crustaceans and polychaetes were the most diverse groups (14 and 11 species richness, respectively). The mean abundance ranged from 79.67±57.47 ind/250 ml to 718.75 ind/250 ml (mean±SD). The amphipod Monocorophium insidiosum, the gastropod Anachis isabellei and the tanaidacean Leptognathia sp. were the most representative species in the mats. Richness and diversity in P. socialis aggregates were higher than in surrounding sediments. Results show significant differences among months in composition, abundance and feeding guilds of the macrofauna associated with the mats. The assemblage of benthic macrofauna with permanent and temporary organisms in P. socialis aggregates suggests the existence of microhabitats in the mats that provide substrate, refuges for predation and availability of food increasing richness and diversity. These results allow considering P. socialis as an autogenic ecosystem engineer in the Mar del Plata harbour.

The red whelk, Neptunea antiqua (Mollusca: Prosobranchia) is a dioecious prosobranch species with internal fertilization, and lecithotrophic larval development. Sexual dimorphism, sexual ratio, the size and age at sexual maturity, and the annual breeding and hatching periods of this subtidal neogastropod were investigated in the central western Irish Sea. Sexual dimorphism was evident as female whelks were larger in both length and weight. Subtle differences in shell morphology were also detected between the sexes. All samples taken together indicated an equal male to female sexual ratio for the studied population. Size and age at sexual maturity were noted to differ between sexes, occurring at 75–90 mm (shell length), or four to five years in males, and 95–110 mm, or six to nine years in females. Quantitative and qualitative techniques identified an annual spawning period between late spring and early summer. Egg masses containing between 14 and 84 egg capsules were observed attached to the dorsal surface of whelk shells in the succeeding months. An average fecundity of 63·78 juveniles was estimated per egg mass deposited. Juveniles were observed to hatch after 6–7 months in laboratory maintained aquaria, indicating a hatching period from October to January in the Irish Sea.

A number of species of ophiuroid are known to occur in dense clusters on the sea-bed. Aggregations of Ophiothrix fragilis (Abildgaard) have been recorded from the English Channel by Allen (1899), Vevers (1951, 1952), Barnes (1955), Ancellin (1957), Cabioch (1961, 1967, 1968), Holme (1966), Warner (1969, 1971), and by Allain (1974). Beds of the same species have been found in the Irish Sea by Jones (1951) and by Brun (1969), on the west coast of Ireland by Könnecker & Keegan (1973) and Keegan (1974), and on the west coast of Scotland, where it is widespread in sea lochs and elsewhere around the coast (McIntyre, 1956, and personal communication, 1975). Records of Ophiothrix fragilis from the North Sea have been summarized by Ursin (1960). In the Mediterranean, aggregations of Ophiothrix quinquemaculata (D.Ch.) have been described by Guille (1964, 1965) from off the south coast of France, and by Czihak (1959) from the Adriatic. Hurley (1959) gives underwater photographs of Ophiocomina bollonsi Farquhar from the Cook Strait, New Zealand. Further examples of aggregation in ophiuroids and other echinoderms are cited by Reese (1966), Mileykovskiy (1967) and by Warner (1978).

A new species of dorvilleid polychaete, Ophryotrocha cyclops, has been observed on the rocky seafloor underneath deep salmonid aquaculture sites on the south coast of Newfoundland, Canada. The distribution of these opportunistic worms is likely related to organic matter accumulation on the seafloor, and this species may have a role in remediation processes. To better understand the functional role of O. cyclops at aquaculture sites, it is important to know what they feed upon. Here, stable isotope analyses (δ13C, δ15N and δ34S) and trace element analyses were performed on dorvilleids and their potential food sources at three aquaculture sites. Stable isotope analyses revealed spatial and temporal variation in the isotopic carbon signature of O. cyclops, highlighting possible differences in the food sources of individual dorvilleids within and between sites. The isotopic composition of dorvilleids was closest to that of fish pellets; the presence of abundant lipid droplets in gut epithelial cells of O. cyclops suggests the assimilation of fish pellet-derived lipids. Trace element analysis indicated that O. cyclops does not concentrate the aquaculture tracers Zn or Cu to a large extent. However, concentrations of sulphur were high in O. cyclops compared with other sources. Taken together, results show that O. cyclops most likely consume both fish pellets and flocculent matter-associated bacteria. As such, they are involved in sulphur cycling and fish pellet degradation at aquaculture sites.