Samples were collected from 10 stations distributed through three sectors in Guanabara Bay during two consecutive years, in order to determine factors that influence the spatial pattern of molluscs and to describe the structure and composition of this community in a eutrophic estuarine system on the Brazilian coast. Although only one species, the gastropod Heleobia australis, comprised 77% of mollusc abundance, 59 species were identified in the bay. In addition to H. australis, three other species were dominant: the gastropod Anachis isabellei and the bivalves Americuna besnardi and Ervilia concentrica. The mollusc communities were significantly influenced by the spatial gradient; the outermost sector has marine conditions, and the other sectors are typically estuarine, leading to differences in the composition and abundance of molluscs. The outermost sector showed the highest diversity, which gradually decreased towards the innermost sector where the dominance of a few opportunistic species is favoured by highly organic mud sediments. Sediment type was strongly correlated with mollusc occurrence in the bay. Guanabara Bay showed two indicator species: the bivalve E. concentrica of the outer sector, and the gastropod H. australis of the intermediate sector. Our results suggest that benthic molluscs in Guanabara Bay show characteristics related to levels of environmental impact. A monitoring programme based on this community is needed to evaluate the effects of human impacts on this community and to monitor changes in its biodiversity in Guanabara Bay.

Three species belonging to the genus Zanclea: Zanclea divergens, Zanclea tipis, sp. nov. and Zanclea exposita, sp. nov. have been described as epizoic of bryozoan from the coral reef of the Bunaken Marine Park (Sulawesi Sea, Indonesia). The record of Z. divergens is the second after its description from Papua New Guinea. Zanclea tipis is characterized by a polymorphic colony and a medusa with very extended exumbrellar pouches. Zanclea exposita shows a naked hydrorhiza creeping on the surface of the bryozoan skeleton.

An evolutionary trend among the Zancleidae, from species epibionts of algae and bivalve shells with the hydrorhiza covered by perisarc to species symbiotic with bryozoan with a naked hydrorhiza, is discussed.

Hydrographic measurements were made on RRS ‘Charles Darwin’ Cruise CD97 of the structure of a Subtropical Ring called STORM discovered south-west of the Azores in October 1995 which moved westward along a latitude near 32·5°N. The results showed an elliptical ring structure with a ratio of minor to major axis of 0·6. The external Ring structure extended across a scale of ~400 km in an east-west direction along the major axis of the structure. The internal structure showed isotherms (isopycnals) that were domed upwards by ~200 m. The swirl transport in the Ring was 44 Sv with a negligible barotropic component and the cyclonic flow extended throughout the water column from the surface (maximum ~50cms-1, at a radial distance of ~100km) with reduced intensity to the sea-floor ~4km depth where the flow was effectively zero. The surface currents and dynamic height data showed that the STORM centre was associated with a ~38cm lowering of sea level. The ERS-1 and ERS-2 altimeter surface signature of STORM revealed a similar structure (~42cm sea level depression) but with a larger scale of influence ~500 km. The remote sensing surface elevation structure derived from altimetry also maps (~-600X) changes in the deeper ocean temperature structure and transport (1 cm change equivalent ~ 1 Sv) in the general region. A ~500 d record from a current meter mooring deployed in the region showed three STORM signatures, each separated by a mean of ~180 days. In June 1996, HMS ‘Hecla’ crossed the North Atlantic at a latitude near 33°N and found three STORM temperature signatures.

INTRODUCTION

Studies on the physical hydrography of the Irish Sea, based mainly on temperature and salinity observations, have been made by Bowden (1955) and Lee (1960). The current systems in various parts of the Irish Sea have been investigated by Bowden & Sharaf El Din (1966), Harvey (1968), Ramster & Hill (1969) and Hill & Ramster (1971). Various smaller-scale physical observations made by other workers have been listed by the above authors.

There are not as many references in the literature to the distribution of nutrient salts in the Irish Sea. Jones & Haq (1963) measured phosphate in Liverpool Bay as part of an investigation into the distribution of the alga Phaeocystis. Slinn & Offlow (1968) have made regular routine measurements of phosphate, nitrate and silicate over a number of years off Port Erin, Isle of Man. Ewins & Spencer (1967) measured phosphate, organic phosphorus, nitrate and silicate in the Menai Straits, and Liss (1969) surveyed the distribution of silicate in the western Irish Sea.

During recent years the Fisheries Laboratory at Lowestoft has investigated the distribution and ecology of plankton and larval plaice in the Irish Sea, and a supporting programme of both physical and chemical hydrographic observations has been made in the area. Ramster & Hill (1969) and Hill & Ramster (1971) have summarized the results of the Lowestoft current measurements. The present paper describes an investigation into the distribution of temperature, salinity, phosphate, nitrate and silicate. The occurrence of Phaeocystis is also reported as an extension of the earlier work by Jones & Haq (1963).

Geographical morphological variations in Fucus vesiculosus populations were studied along the coast of Iceland. Principal component analysis (PCA) based on 11 morphological characters clustered the 26 sampling sites into four different morphological types as follows: (1) a morphological type found along the S-SW-W coast; (2) an intermediate form comprising only two populations in the NW; (3) a type found along the N-NE-E-SE coast; and (4) a type found independent of geographical area, in estuaries and at sites influenced by large freshwater outflows. Populations influenced by low salinity had significantly (P ≤ 0·001) shorter thalli, a shorter distance from the holdfast to the oldest dichotomy, smaller fronds, narrower stipes and midrib width compared to the morphology of all other more saline populations. No significant difference in frond width was found between the S-SW-W and the N-NE-E-SE populations. However, significant (P ≤ 0·001) morphological differences between them were observed, the former having shorter thalli, a greater distance from the holdfast to the oldest dichotomy, narrower stipes and smaller midrib width compared to the latter.

Tubifex costatus is a marine euryhaline species of tubificid, commonly found in brackish water. It is common in estuaries, where it colonizes a wide variety of substrata.

The species breeds sexually once a year in early summer, and it is likely that it takes 2 years to reach maturity, and after breeding it dies.

There is only one likely predator, Nereis diversicolor, and the population of T. costatus seems to be kept at a very constant level.

The function of intersex individuals in three intertidal hermit crab species (Clibanarius antillensis, C. sclopetarius, and C. vittatus) was investigated and a description of the morphology of the gonopores of laboratory-reared intersex individuals before and after moulting provided. Observations on the reproductive behaviour revealed that intersex individuals of these hermit crab species copulated successfully as males with normal females. Intersex individuals showed morphological alterations indicating closure of the female gonopores after moulting. These findings associated to information on behaviour and population biology of hermit crabs may suggest that hermit crab intersexuality may be part of a true hermaphroditism mechanism.

A method is described for obtaining the venom from the dorsal fin of the lesser weever without harming the fish. It is suggested that the amount of venom normally injected into the wound by the weever when it stings is O-5-O-2 mg dry weight of venom. Some 60% of the dry weight of the venom appears to consist of toxic muco-substances, which have a neurotoxic effect, but are without toxic effect on the blood. In extracts this fraction may be separated into two albumins and an amino polysaccharide, though in the native venom these are probably associated into a single complex mucosubstance. When injected subcutaneously this fraction of the venom produces no local pain. The venom also contains about 1-20 jug/mg (dry-weight basis) of 5-hydroxytryptamine which appears to be the origin of the pain of the sting, together with some undetermined histamine releaser (not an indole) of low molecular weight. It is suggested that the chief role of the 5-hydroxytryptamine in the venom is to produce pain around the area of the inflicted wound.

Most of the work on temperatures lethal to fish has been reviewed by Brett (1956). Most of the fish have been adults of freshwater species, and it has been found that both upper and lower lethal temperatures vary with the species, the temperature of acclimatization and the duration of time the fish are subjected to the test temperature.

This field study examined competition for space among encrusting bryozoans on artificial panel substrata used to simulate the habitat found on the undersides of boulders. In all 1761 interactions were analysed, involving 16 species of cheilostomes (genera Callopora, Celleporella, Cribrilina, Electra, Escharella, Escharoides, Haplopoma, Membraniporella, Microporella, Phaeostachys, Schizomavella, Schizoporella and Umbonula) and two ctenostome genera (Alcyonidium and Flustrellidra). Neither absolutely transitive nor intransitive arrangements of competitive outcome occurred among the species. Instead, the high incidence of ‘ties’ and reversals of outcome produced a network-like arrangement. In terms of outcome alone Escharoides coccinea (Abildgaard), Membraniporella nitida (Johnston) and Schizoporella unicornis (Johnston in Wood) were apparently ‘overgrowth dominants’, Alcyonidium spp. and Cribrilina cryptooecium Norman were ‘intermediate dominants’ and Callopora lineata (L.), Callopora craticula (Alder), Celleporella hyalina (L.) and Electra pilosa (L.) were ‘inferior competitors’ for space. The effects of four variables on the outcome of specific competitive encounters were assessed in detail and included (i) the identity of the colony encountered, (ii) the angle of contact between the competing colonies, (iii) the location (two sites, on both the east and west coasts of Scotland) and (iv) the year (1983, 1984). Models incorporating these variables were developed, using the Generalized Linear Interactive Modelling System (GLIM), to examine their influence on the outcome of bryozoan encounters. All of these factors contributed to explaining the considerable variability in the outcome of competitive interactions. The species were not, however, affected equally by all the variables, although encounter angle and year were significant for dominants and encounter angle, site and year all were significant for intermediate species.

A new kinorhynch genus and species is described from coralline sand collected on the atoll of the Chuuk Islands, Micronesia. The new genus and species, Triodontoderes anulap gen. et sp. nov., is characterized by having an introvert with only five scalid rings, segment 1 consisting of one tergal and one sternal plate, segments 2 to 4 of one tergal and two sternal plates, and segments 5 to 11 of one tergal plate with midventral articulation. Triodontoderes anulap gen. et sp. nov. shares several characters with species of Zelinkaderes, including reduced number of scalid rings, distally tripartite placids, a trunk being circular in cross-section, and segments 5 to 10 being composed of a single tergal plate with midventral articulation. Until the kinorhynch relationships have been examined in a formal phylogenetic analysis, Triodontoderes gen. et sp. nov. are tentatively assigned to Zelinkaderidae.

Some preliminary observations on luminescence in polynoid worms have been presented in a previous paper (Nicol, 1953). These animals produce light in scales (elytra) which cover the dorsal surface of the body. The source of the light lies in a layer of unicellular epithelium on the lower surface of the scale. Histologically, this tissue consists of columnar cells (photocytes), characterized by the presence of coarse eosinophilic granules in the cytoplasm. The nervous supply of the elytrum derives from a nerve trunk which ascends the stalk or elytrophore and proceeds to a ganglion in the centre of the scale. From this ganglion nerves radiate peripherally and proceed to the photocytes, and to sensory receptors on the dorsal surface and at the margin of the scale (Bonhomme, 1942).

A seasonal variation is found in the ovaries of immature hake (Merlucius merluccius L.).

There appears to be a seasonal change in the rate at which young eggs are formed from resting oocytes, as indicated (1) by the change in the relative abundance of nuclei in synapsis, and (2) by the change in the average diameter of the eggs in the egg-stock in the ovary. These processes show considerable correspondence in their season of incidence with the ovarian cycle of the mature and adolescent fish.

A physiological rhythm has now been detected in both somatic tissues and gonad in the immature hake, which foreshadows the physiological rhythm associated with the spawning cycle in the mature hake. The implication of this on the question of the formation of “growth-rings” in the skeletal structures is briefly discussed.

Details of the gross cellular changes taking place in the gonadial tissues and coelom of Ficopomatus during the annual reproductive cycle are presented. There is no true gonad in either sex; instead, germ cell precursors are produced by divisions of a germinal epithelium associated with the ring blood vessels in the intersegmental septa.

Segments producing gametes do not all develop simultaneously; the posterior segments are generally at a more advanced stage of sexual maturity. The later stages in gamete development take place free in the coelom, where nourishment is supplied presumably by the mobilization of materials formerly stored in tissues surrounding the gut.

Spawning commences in June and continues through to October, with peak activity coinciding with the period of high water temperature in August and early September. The adult population comprises males, females, and protandrous hermaphrodites which in the male phase become sexually mature in advance of the rest of the population, and as females later on. These transitional individuals are thought to contribute a negligible amount to the effective reproductive output in those populations living where there is marked temporal constraint on the period of reproduction.

The different reproductive capacities of temperate and tropical Ficopomatus are considered.

The stomach contents of Lepidion eques trawled at depths ranging from 500 to 1250 m on the Hebridean Terrace (56°-57° N, 9°-11° W) are analysed relative to size of fish, depth of habitat and season of the year. Of the 1281 fish examined, 47% had everted stomachs, 29% empty stomachs, 2% had food that was totally unrecognizable while 21% had food whose constituents could be identified. The principal dietary components are the epibenthic and hyperbenthic decapod crustaceans, although a wide variety of other organisms also occur as minor components. Benthic infauna and sessile epifauna are absent from the diet. L. eques therefore feed predominantly on organisms swimming immediately above the sea-bed or actively moving over it.

The background and aims of this study are outlined in the introductory section of the preceding paper (Vanosmael et al. 1982).

The type species of Platychrysis, P. pigra, was described by Geitler in 1930 from a sample taken at Las Palmas in the Canary Islands (Geitler, 1930). It was later recorded by Carter in 1937 from a brackish pool at Bembridge, Isle of Wight, and a more complete description of the species was given, including a description of the motile cells (Carter, 1937). A taxonomic comparison of the three genera Prymnesium J. Massart, Chrysochromulina Lackey and Platychrysis Geitler was published by Conrad (1941), whose Belgian records for the species (Lilloo) were subsequently published in 1954 (Conrad & Kufferath, 1954). In 1967, Norris (Norris, 1967) described a new species, P. neustophila, recorded from Puerto Peñasco (Mexico), but this species needs further investigation since the account is somewhat incomplete.

The distribution of the visual pigments within the retina of the rudd, Scardinius erythrophthalmus, and dragonet, Callionymus lyra L., was studied by measuring the spectral absorbance of small areas of intact isolated retinas.

The rudd retina contains two visual pigments, VP 5O71 and VP5352. There is a progressive change in the relative proportion of these two pigments in the dorso-ventral plane, and there are no sharply defined zones each with a different pigment mixture. The proportion of the A1-based pigment (VP 5071) is greater in the dorsal part of the retina.

The maximal optical density of the pigment in the dorsal retina of the rudd was greater (about o·6) than it was in the ventral retina (about 0·3). The difference in the amount of light absorbed, however, is small compared to the intensity difference between the up-welling and downwelling light of the environment. When the relative proportion of the A1- and A2-based pigments was changed by altering the lighting conditions under which the animals were kept there was little or no change in the maximal optical density of the pigment.

In the dragonet the retina shows a clear division into a ventral pink zone (maximal optical density about 0·5) and a dorsal zone that is much paler (maximal optical density about 0·2). The relative spectral absorbance of the two regions is similar, although one is said to be a pure cone region, and the other to be dominated by rods.

The spectral absorbance curves for the intact retinas agreed well with results obtained with pigment extracts.

Field data on the pelagic occurrence of Corophium volutator were obtained in 1981–82 in the Dollard (Ems estuary). The pelagic population density averaged over a tidal half cycle was in the range 0–15 m-3. The pelagic population represents about 0.06% of the benthic population. On most sampling days pelagic occurrence resulted in a net flood surplus transport.

The first data substantiating the occurrence of diarrhetic shellfish poisoning (DSP) in the central region of the Adriatic Sea (Kaštela Bay) in the summer of 1995 is presented. Toxicity was investigated using bio-assay and HPLC-FD analysis. Analysis of samples displaying toxicity, in addition to small concentrations of okadaic acid (OA), suggested the presence of an unknown derivatized compound at high concentration. A long term survey of the phytoplankton community has been conducted. The origin of mussel toxicity was traced to Dinophysis sacculus, a suspected toxic species.