The sea stickleback, Spinachia spinachia, lives in shallow coastal and estuarine waters where the male builds a nest and undergoes a protracted period of parental care. The accumulation of silt in the nest has been suggested as one of the environmental factors that regulate nest-directed activities during the parental phase. Experiments have quantified the behaviour of the male fish before and after the application of silt to the nest and shown that some behaviours are affected. The fanning activity, attendance at the nest and other nest-directed activities were examined and it was found that nest inspection and nest pushing increased significantly following the application of silt. Fanning activity, a major part of the parental behaviour of the sticklebacks, was unaffected by the experimental treatment and seems to be unresponsive to environmental changes. The results are discussed in relation to the functional significance of parental behaviour, and compared with a closely related species.

Gills are the typical respiratory organ of fish in their usual habitat of well-aerated water. The transition from water- to air-breathing required many modifications to the structural and physiological adaptations of the gas-exchange surfaces, i.e. gill, skin, swimbladder and other accessory organs of the alimentary canal. The skin is particularly important among air-breathing fish. This histological study showed varying degrees of adaptation of parts of the skin from different body regions, paying particular attention to the water/blood barrier. The results suggest a general importance in gas exchange in the following order: gill, inner operculum, nasal, body and outer opercular skin, as indicated by increasing thickness of the water/blood barrier.

Prey populations, patterns of availability, and dispersion of prey can have farreaching effects on numbers and range-sizes of terrestrial Carnivora (Macdonald, 1983; Kruuk & Parish, 1982; Kruuk & Macdonald, 1985). These parameters may therefore also affect populations of otters Lutra lutra, living in the sea around Shetland, U.K., as well as populations of fish-eating birds there. This paper presents observations on fluctuations in numbers and activity of several species of demersal fish, over a 3½ year period, along a coast in Shetland. It aims to provide information on the distribution and availability of these species to some predators, especially to the otter, but also to the heron Ardea cinerea, the black guillemot Cepphus grylle and others.

The mechanisms of accumulation of zinc and cadmium by the marine polychaetous annelid Neanthes arenaceodentata (Moore) have been studied. Animals have been exposed to EDTA chelate buffered sea water containing 65Zn and 109Cd. The calculated free ion activities of the zinc and cadmium in the sea water were 10-8.13 M and 10-7.65 M, respectively. Uptake occurs from the free ionic pool of metal and EDTA and EDTAmetal complexes are largely excluded from the animal. In unfed animals, the metals accumulate linearly with time at a rate which decreases when the temperature is reduced but increases in the presence of metabolic inhibitors. Experiments using [14C]EDTA as an extracellular marker indicate that the observed increase in accumulation caused by the inhibitors is at least partially due to media entering extracellular anatomical compartments such as the coelom and lumen of the gut which are normally isolated from the seawater by cilia or sphincters.

An event/time recorder is described which is contained in a sealed waterproof case, with no external electrical connections and which uses novel methods for communicating control and data signals, and for charging the internal battery. The instrument is designed to be used underwater for recording behavioural and faunistic census information. On return to the laboratory the data can be retrieved, stored and processed using a microcomputer. The instrument is uncomplicated to use, completely waterproof, of a size that is easily carried and robust enough to withstand hard usage.

Scientific data from the last 100 years are combined with primary and secondary historical information on the fisheries to summarize changes in the relative abundance of pilchards and herrings in the south-west in the last 400 years. The fluctuations in the two species are compared with recorded and inferred annual mean temperatures over the period. Pilchards are more abundant and extend farther to the east when the climate is warmer, as from 1590 to 1640 and from 1930 to 1960. In cooler times, as in the second half of the seventeenth century, herrings are more abundant while the pilchard fishery occurs later in the year and is restricted to west Cornwall. Lesser changes in the relative abundance of the two species and the timing of the fishery along the south coast of Devon and Cornwall in the intervening periods between these extremes accord fairly well with smaller fluctuations in climate. It is presumed that in addition to direct effects on reproduction and behaviour, changes in climate can indirectly influence the relative competitive advantage of the species through alterations in the associated ecosystem.

When red blood cells are subjected to mechanical stresses, they change shape with very little resistance. Such deformability of erythrocytes plays a crucial role in their function and survival in the circulation since they must undergo large deformation whenever they pass through narrow capillary vessels. While this mechanical characteristic of erythrocytes has been attributed to their unique cellular structure, it has also been shown that considerable alterations in this property result from changes in cellular metabolism and in surrounding plasma physicochemistry (Weed, LaCelle & Merrill, 1969; Kikuchi & Koyama, 1984a, b). It might be supposed, therefore that red blood cell deformability would be modified, when animals are exposed to different environmental conditions, with significant effects on their acclimatization or survival under the varied conditions. However, little is known of this aspect of fish cardiovascular physiology.

Glass eels of the American eel Anguilla rostrata (Lesueur) utilize selective tidal stream transport, a series of semidiurnal vertical migrations in phase with the tide, to migrate up the Penobscot River estuary, Maine, U.S.A., in the spring. Glass eels, freshly collected during their migration, exhibited rhythmic activity with circatidal periodicities when tested in groups in the presence of a water current under constant conditions in the laboratory. Freshly collected groups of eels which had already completed their migration through tidal water did not exhibit circatidal activity rhythms under the same conditions. The activity rhythms of groups of eels freshly caught in tidal water appeared to be entrained by a 12.5 h cycle of water current reversals, but not by a 10.0 h cycle of current reversals. In other entrainment experiments water collected on flood and ebb tides was alternately added to the experimental tanks every 5.0 h. Under these conditions groups of eels freshly caught in tidal water did not display any rhythmic activity. Only 2 of 100 glass eels, freshly collected from tidal and non-tidal water, which were tested individually in static tanks, exhibited rhythmic activity. The activity rhythms would allow an eel to time its vertical migrations in the estuary despite varying environmental conditions.

The effect of increasing the temperature of Mytilus edulis by 10 °C is to increase the rate of 65Zn uptake. If the temperature is oscillated through this range there is a further enhancement of metal uptake. The effect is associated with a decrease in cytosol metal and an increase in granular fractions. These unexpected results are interpreted in terms of cellular metal-ligand homeostasis.

Samples collected from power station intake screens between 1972 and 1977 have been used to study aspects of the biology of the whiting in the Severn Estuary and Bristol Channel. 0+ whiting generally started appearing in the inner estuary in July, at which time their standard length was at least 38 mm. Their numbers peaked in October and subsequently declined particularly rapidly during the wet winter of 1976/7 when salinities were frequently below 10‰. The size of 0+ whiting in the late autumn and early winter was generally less in the shallows of the Inner Severn Estuary than in neighbouring deeper waters and in the Inner Bristol Channel. Growth rates of 0 + whiting fell within the range of those recorded for the North Sea, but below those generally found in inshore waters and sea lochs on the west coast of Scotland. Following their immigration into inshore waters in the Bristol Channel and Inner Severn Estuary, young whiting became infected with the copepod parasites Lernaeocera branchialis and Clavella adunca and the metacercariae of the heterophyid digenean Cryptocotyle lingua. Prevalence of infection was less in 0+ than older fish and infection by L. branchialis caused a significant decline in condition. As whiting became larger, the main site of attachment of Clavella adunca changed gradually from the wall of the branchial chamber to the primary rakers of the first gill arch. Vertebral counts suggest that the whiting which enter the Inner Bristol Channel and Severn Estuary are not representatives of the populations found in the Irish Sea.

The Pogonophora are tube-worms of predominantly deep sea distribution. They lack a functioning alimentary canal in the adult stage and are then dependent for nutrition on internal symbiotic chemosynthetic bacteria that occupy tissue derived from the larval endoderm (Southward, 1982, 1987, 1988; Southward & Southward, 1987; Southward et al. 1981). Of the two main subgroups, the small perviate Pogonophora are widely distributed in reducing sediments in the oceans, while the large vestimentiferan or obturate Pogonophora are restricted to hydrothermal vents or cold seeps. The small Pogonophora are often most abundant on steep slopes and in the Bay of Biscay Siboglinum atlanticum (Southward & Southward, 1958) can be a dominant element of the infauna of the sediments on the sides of canyons. This animal, like other small Pogonophora, lies buried in the sediment, in contrast to the vestimentifera which are attached to hard substrates. Until now there has been no fully quantitative information on the distribution of S. atlanticum and associated pogonophores of the Bay of Biscay. Dredges or trawls have been used for most previous sampling of pogonophores along the continental slope (Southward, 1979, 1985). Even the Plymouth-pattern deep-sea anchor dredge (Southward & Southward, 1963), which is designed to dig into the sediment immediately it is towed on the bottom, may drag for some distance through soft sediments before digging in, and then samples the upper few centimetres over a wider area than its mouth opening. During the last season of operation of R.R.S. ‘Frederick Russell’, before this vessel was disposed of by N.E.R.C., opportunity was taken to make a combined quantitative biological and chemical survey, using box-corers. The samples from the corers were large enough to allow the sample to be used for assessment of the population density of the pogonophores and analysis of sediment chemistry. Some inferences can now be drawn about the factors controlling pogonophore abundance.

This work reports on the fine structure and histochemistry of several regions of the alimentary canal in Pholoe minuta (Fabricius, 1780). Particular emphasis is placed on the elaborate secretory cells (tryptophan-containing secretion) associated with the pharyngeal jaws. Mucus gland cells were located and described for the oesophagus (acid mucins), pharynx papillae (sulphated acid mucins), pharynx luminal lining (mixed acid mucins) and the intestine (mixed acid mucins). Enzymic gland cells (zymogen-like secretory granules) were identified in the luminal lining of the pharynx and in the intestine. Lysosome-containing cells (presumably absorptive) were described in the intestine. Glycogen reserves were observed along the coelomic peritoneum and a seasonal pattern for their deposition and utilization is briefly discussed.

Two sabellariid polychaetes, Sabellaria alveolata from European waters and Phragmatopoma californica from the west coast of North America, are known from previous work to have larvae that settle and metamorphose preferentially on the cemented sand tubes of conspecific adults. The naturally occurring inducers of larval metamorphosis were recently isolated and identified for P. californica. In the present study, larval behaviour of S. alveolata and P. californica was compared in reciprocal laboratory settlement assays. For both species, metamorphosis occurred to a greater extent on conspecific tube sand than on control sand or on heterospecific tube sand. Extraction of the tube sand of S. alveolata with organic solvents diminished its capacity to induce metamorphosis pi conspecific larvae, but this capacity was not transferred to the extracts, as was the case for P. californica. The substance responsible for the enhanced metamorphosis of S. alveolata on conspecific tube sand remains unknown. The free fatty acid (FFA) inducers of larval metamorphosis of P. californica either inhibited, or had no effect on, metamorphosis of S. alveolata. Both species responded abnormally upon exposure to unnaturally high concentrations of certain (particularly polyenoic) FFAs. Abnormal larval responses of S. alveolata, however, did not incorporate behavioural components of normal metamorphosis, as were observed for P. californica. FFAs were isolated from the natural tube sand of S. alveolata at less than one-tenth the concentration found in the natural tube sand of P. californica. The differences between the two species provide further evidence that a very specific mechanism is responsible for the perception of FFAs by the larvae of P. californica.

The marine plankton contains an extremely diverse assemblage of ciliates which may be important in planktonic energy flow (e.g. see Burkill et al. 1987; Porter et al. 1985; Rassoulzadegan & Sheldon, 1986; Sherr & Sherr, 1987; Stoecker, Michaels & Davis, 1987; Verity, 1987). Many marine ciliates are delicate in nature and until recently have been poorly collected. Thus, they are often entirely missed in plankton sampling. During an investigation of the role of planktonic ciliates at the Isles of Shoals, Gulf of Maine (Montagnes & Lynn, 1988; Montagnes, Lynn, Roff & Taylor, 1988) samples were Bouin-fixed to preserve these delicate species. The ciliates were subsequently quantitatively protargol silver-stained to estimate species abundances and biomass (Montagnes & Lynn, 1987). This staining method, in addition to providing quantitative estimates of abundance and cell volume, gives invaluable taxonomic information by revealing cellular structures. Thus, it has been possible to compare the ciliates from the Gulf of Maine with described species.

A hypothesis about the biogeography of Isistius brasiliensis in the north-eastern Atlantic is formulated through the study of frequency, size and geographic distribution of crater wounds, produced by this shark on swordfish (Xiphias gladius) and other large pelagic vertebrates. The results suggest that the bulk of the population of adult I. brasiliensis is found between 11° N and 16° N. Probably there are nursery areas in more southern latitudes. Large individuals would be frequent northwards of 16° N parallel.

Young vestimentiferans, ranging from 0.15 to 10 mm in length, were examined by light and electron microscopy (SEM and TEM). The newly settled stages have a functional gut and traces of larval ciliation, which suggests that they may have developed from a planktonic trochophore stage. The larval mouth becomes an elongated siphon and the ciliated gut persists for some time after the development of the bacterial symbiosis in the trophosome. The segmentation of the body in the earliest stages is similar to that in postlarval Pogonophora, and it is concluded that Vestimentifera and Pogonophora are closely related.

The genus Ampelisca comprises more than 150 species and is one of the more important benthic genus of marine amphipods. New species are regularly added (Barnard & Agard 1986; Bellan-Santini & Marques, 1986; Goeke, 1987). Ampelisca are found from the intertidal zone to abyssal depths but most of them live on the continental shelf. In spite of many studies, it is often difficult to distinguish some species which are morphologically similar. In the last ten years, twenty-two species have been described from the north-eastern Atlantic (BellanSantini & Kaïm-Malka, 1977; Bellan-Santini & Dauvin, 1981, 1986; Dauvin & Bellan-Santini, 1982, 1985; Bellan-Santini & Marques, 1986). Materials come from MNHN of Paris collection, collected by Chevreux (1894–1924) (Dauvin & Bellan-Santini, 1985, 1986) and specimens collected during the last 25 years. All these new species are described from the Atlantic coast from northern Brittany to the Sahara and from the Mediterranean Sea.

In an attempt to describe the physical and chemical characteristics of the sediments as an environment for the invertebrate benthos, a total of 273 stations covering the sector from 56° N to 61° N in the North Sea was sampled. The sediment samples which were collected by grab and corer were analysed for particle size (as well as silt-clay content and sorting), organic carbon, plant pigments and trace metals (Cd, Pb, Zn, Ni, Co, Cu). On a smaller scale a few stations were sampled for redox potential, pH and pesticides.

Taking into account the geological history and the on-going hydrographic processes, explanations for the formation of the sedimentary provinces in the North Sea were provided. The sediments were predominantly fine to medium sand, but there was a depth-related gradient with the finer grades, organic carbon and, to a lesser extent, plant pigment being found in the deeper sedimentation basins of the Fladen Grounds and Norwegian Trench.

Trace metals and pesticide contaminants associated with the finer organic and inorganic fractions were higher in the sediments of the above deeper areas as well as in the vicinity of estuaries. It could be concluded that despite the enhanced concentrations of Cd, Ni, Pb and Co, at the east of Shetland, which were due to a geochemical anomaly, there was no evidence of any important or large-scale contamination of the North Sea as a whole.

Relationships between respiratory area, oxygen consumption, and body mass have been examined during the development of water- and air-breathing fish. It is concluded that there is at least one stage at which the slope of the relationship between log gill area and log body weight changes during fish development. This usually occurs in the weight range 0.05–1.0 g and is often associated with a distinct metamorphosis, but no common functional significance can be attached to them. However, the change in slope does not appear to be associated with a comparable inflexion in the corresponding relationship between body mass and oxygen consumption (routine). It seems probable that other surfaces are important during these transitions and that the total gas-exchange surface of the fish shows a more constant change throughout the life history. Further analyses of a wider range of species is required to test this hypothesis.

Fourteen specimens of the hepatopancreas of the Pacific white shrimp, Penaeus vannamei, were prepared for examination with the transmission and scanning electron microscopes and with the light microscope. The histology and ultrastructure of this organ is similar to that seen in other Decapoda. At the ultrastructural level, it was observed that B-cells rupture at approximately the level of gap junctions located on the lateral plasma membranes of the cells, and discharge the contents of their large vacuoles into the intercellular space. This efflux of enzymatic material may be the mechanism by which cells are released from the wall of the tubule at the proximal end: the rupture and collapse of a B-cell may be analagous to the removal of the keystone which supports an arch. Deprived of support, and lacking structural adaptations for cohesion (there are no desmosomes or interdigitations in the epithelium) and with the intercellular material digested, the remaining intact cells collapse into the lumen of the tubule. The lysis of individual cells of all types - R-, F-, and B-cells - may contribute to the tubules’ total complement of digestive enzymes.