It has been suggested by Pettibone (1953) and Lwebuga-Musaka (1970) that the elytra of scaleworms may function in respiration, not as the sites of gaseous exchange, but rather the means by which respiratory water currents were created over the dorsum. A role in sensory perception was also postulated (Pettibone, 1953). However, no detailed morphological study accompanied this work. To date the scales of only a few polychaete species have been examined ultrastructurally, and these studies have focused mostly on cuticular features (Anton-Erxleben, 1977, 1981a, b). Considerable attention has been focused on the bioluminescent properties of the elytra of the scaleworm, Harmothoe lunulata (Delle Chiaje) (see Bassot, 1979; Nicholas et al. 1981, 1982). Other morphological features of Pholoe minuta studied at the ultrastructural level include gametogenic (Heffernan & Keegan, 1988a) and larval (Heffernan & Keegan, 1988b) stages as well as the digestive tract (Heffernan, 1988). There are several reports on the ultrastructure of polychaete gills (Storch & Welsch, 1972; Spies, 1973; Storch & Alberti, 1978; Menendez et al., 1984; Storch & Gaill, 1986). These works have recently been reviewed by Gardiner (1988). This study describes the fine structure of the scales of Pholoe minuta and the features illustrated here are in agreement with a role in respiration and sensory perception.

The annual reproductive and somatic cycles of the brittlestar Acrocnida brachiata are described using gonad and gut indices for intertidal and subtidal populations in the Bay of Douarnenez, France. Oocyte size frequency diagrams complement the gonad study in the subtidal population. Clearly marked reproductive cycles are defined in both populations. Accelerated gonad growth takes place in spring and the gonads reach the peak of development in May-June each year. Spawning is completed by the end of August. Oocytes reach a mean diameter of 150 μm and a new generation of oocytes appaears in the ovaries during the spawning period. The gut indices show a clear inverse relationship with the gonad indices in the intertidal population, but this relation is not well revealed in the subtidal population.

The skeleton and calicoblastic ectoderm of the scleractinian non-zooxanthellate coral Caryophyllia smithii were investigated by light microscopy, scanning and transmission electron microscopy. Except for some costal spines, the skeleton was fasciculate. Fasciculi were made up of bundles of crystalline needles, each crystalline needle consisting of a number of linear series of small (<1 μm) rounded crystals. Fractured skeletons showed the fasciculi to be arranged into layers and that within some septa, theca and costal spines there were spaces that contained neither mineral nor organic matter. These spaces could also be found at the growing edges of septa and theca. Demineralization of the skeleton revealed an organic matrix whose configuration mirrored the architecture of the skeleton. In areas of the skeleton where deposition was occurring the overlying calicoblastic ectoderm was relatively thin with prominent intercellular spaces and secretory vesicles. In contrast, over non-depositing areas the calicoblastic ectoderm was thick and contained residual bodies, nematocysts and membrane-bound granules. The results are compared and contrasted with those from scleractinian corals that have endosymbiotic zooxanthellae.

Mycteronastes undulatae gen. nov., sp. nov. (Monogenea: Monocotylidae) is described from the nasal cavities of Raja undulata caught off Arcachon in France and off Lisbon (Tagus estuary) and Sines in Portugal. Merizocotyle icopae Beverley-Burton & Williams, 1989, be-comes Mycteronastes icopae n. comb., the type species of Mycteronastes gen. nov. Similarities between M. icopae and M. undulatae include the arrangement of the haptor loculi and hooks, the general disposition of the reproductive system, the presence of eyespots and the habitat (the nasal cavities of the host). However, a distinctive feature is the absence of a copulatory sclerite and bulb in M. undulatae. The diagnoses of the following taxa are amended: Monocotylidae, Merizocotylinae and Merizocotyle.

Haliotis tuberculata L. densities and population distributions were assessed for 13 sublittoral sites around the coasts of Jersey, Channel Isles using SCUBA techniques. Twenty 1 m2 quadrats were assessed at each site at 5 m below lowest spring tide level (LSTL). Mean densities at each site ranged from 0·05 animals m−2 to 2·35 animals m−2, while the overall mean for the whole island was 0·79 animals m−2 (s.e.=0·24). Population density (D) declined with increasing mean animal length (LTH). The slope of the equation relating loge D to loge LTH was -6·92. Data collected at 2 m, 5 m, 8 m and 10 m below LSTL at two sites showed no trend in mean animal length with depth at one of the sites, but it did increase slightly with depth (1·3 mm nr−1) at the other.

An appendicularian belonging to the family Oikopleuridae, subfamily Bathochordaeinae, Mesochordaeus bahamasi gen. nov., sp. nov., is described from a single specimen collected at mesopelagic depth in Bahamian waters. As the subfamily was founded with only one genus (Bathochordaeus), new descriptions are given for the subfamily and the two genera.

Lasaea rubra is an inbreeding bivalve species, living at most heights on rocky shores. Freshly collected animals from different shore heights showed significantly different upper median lethal temperatures (MLTs), with upper shore animals having higher MLTs than lower shore specimens. Experiments with animals acclimated for at least one month to a single temperature (15°C) demonstrated that these differences in upper MLT were unaffected by thermal acclimation. Electrophoretic investigation showed that the differences in thermal response had a genetic basis. Homogeneous populations of the high-water inbred line (‘Inbred line A’) had a higher MLT than homogeneous populations of ‘Inbred line C’ which was found on the middle and lower shore. No differences were detected between the MLTs of separate populations of Inbred lines A or C. A third inbred line (‘Inbred line B’) was found on the middle shore, but no homogeneous populations were found. However, indirect evidence suggests that Inbred line B has a thermal response intermediate between those of Inbred lines A and C. Study of populations made up of mixtures of inbred lines confirmed the relationship between upper MLTs and genetic composition of the population.

Post-larval specimens of Hirundichthys affinis are capable of jumping out of water, but the pectoral and pelvic fins are not extended when in air. Penetration through the air/ water interface demands a force to overcome surface tension which is similar in magnitude to the force required for the jump itself. However, post-larvae do not produce the single propulsive tail flick which powers the jump until most of the animal has passed through the interface. The post-larva emerges at an angle close to 45°, thus maximising the horizontal distance travelled before re-entry.

Whether swimming slowly (4 body lengths s-1), or at maximum speed (36 body lengths s-1), post-larvae swim with the pectoral and pelvic fins extended. Calculations show that fast swimming post-larvae operate at Reynolds’ numbers of about 4×103, where surface roughness and projections decrease rather than increase drag.

Chlorophyll analysis and methods of direct observation of rock surfaces under the SEM were used to estimate composition and abundance of epilithic microbial taxa. Effectiveness of different chlorophyll extraction techniques was assessed. Extraction from ground and intact rock was compared using both hot methanol and acetone extraction methods. Hot methanol extraction from intact rock provided the most accurate and precise estimates of chlorophyll content. SEM preparation methods were compared. Microbial taxa were counted under the SEM from cryostage, critically point dried and air-dried material. It was concluded that air drying was the most appropriate preparation method for SEM observation. Air drying provides reasonable estimates of microbial composition and abundance and was less time consuming so allowing an adequate number of samples to be analysed. Cumulative species number with sampling effort curves were used to establish minimal sample sizes with respect to estimates of species number. Sequential estimates of mean abundance with increasing sample size were used to determine the effects of increasing sample size on estimates of abundance of the dominant taxa. These estimates were compared at different times of the year and for two different locations. Microbial communities were found to be extremely patchy in distribution. However, sample sizes required to give good estimates of taxa number and abundance were established. These estimates were found to be similar for the main taxa at different times of the year and at different locations.

The leatherback turtle, Dermochelys coriacea (L.) studied was a male, weighing 916 kg, with a total dorsal length of 291 cm. It was beached on the Welsh coast, UK in September 1988 and is currently the largest leatherback ever recorded.

Total lipid formed between 87.5 and 95.4% of the dry weight of representative samples of the blubber and 43.0% and 4.9% of the liver and pectoral muscle respectively. High levels of neutral lipid in the liver (79.0% of the total lipid) as well as the blubber (87.6–99.9% of the total lipid) suggest an important energy storage function for these tissues.

Overall, with the notable exception of 22:lwll, fatty acids which are found in a putative jellyfish diet of Rhizostoma, Amelia, Cyanea and Chrysaora are also present in the leatherback liver and muscle, blubber and other fatty tissues. Fatty acid 22:lwll is present in the jellyfish samples, but is absent or at trace levels only in the leatherback tissues (0.1–0.3% of the total fatty acids).

The polyunsaturated fatty acids of the w3 series 20:5w3, 22:5w3 and 22:6w3 are well represented in leatherback adipose tissues, muscle and liver as well as in the jellyfish examined. The leatherback and jellyfish lipids are therefore marine in character, but are also similar to terrestrial animal lipid in having a high proportion of fatty acids of the w6 series, principally arachidonic acid, 20:4w6. The significant levels of 20:4w6 in jellyfish total lipid (9.7–20.0% of the total fatty acids) and in the leatherback neutral lipid (1.0–10.9% of the total fatty acids) and phospholipid (0.6–15.5% of total fatty acids) fractions of all tissues sampled suggests that arachidonic acid assumes more importance in food chain relationships involving leatherbacks than in other marine food webs such as those involving fish.

The spawning, larval development, and postlarval characteristics of Calliostoma granulatum have been described and illustrated from laboratory observations. Spawning in this species does not follow a seasonal pattern, since adult specimens caught at all times of the year released viable gametes after two or three days in tanks. Eggs had a mean diameter of 341 μm and were surrounded by a mucous sheath by which they were agglutinated into ribbons of variable length that formed amorphous clumps on the bottom of the tanks. The veliger larval stage was short (two days) and took place inside the egg membrane. Development was direct, and at 18–19°C juveniles emerged as crawling young four days after fertilization. Larval and postlarval shells were studied with the aid of a scanning electron microscope.

Summer outbreaks of Gyrodinium aureolum in European coastal waters have been described since 1966 (Braarud & Heimdal, 1970). The coincidence of G. aureolum blooms and observations of noxious effects on fauna (Widdows et al., 1979; Tangen, 1977; Jones et al., 1982; Southgate et al., 1984; Potts & Edwards, 1987; Thain & Watts, 1987) is well documented. However, great differences in toxic effects have been found in in vitro studies (Partensky & Sournia, 1986), with critical cell densities varying from 6×105 cells 1−1 to 3×107 cells 1−1. Production of a lethal agent has been suggested by Turner et al. (1987). More recently, the toxic principle has been identified by Yasumoto et al. (1989).

Changes in dietary lipids (fatty acids, sterols and fatty alcohols) during herbivory and coprophagy by the annelid worm Hediste (Nereis) diversicolor (O.F. Müller) were modelled in laboratory feeding experiments. The dinoflagellate Scrippsiella trochoidea (Stein) was used as the food in herbivory; faeces from the crustacean Neomysis integer (Leach) after feeding on this same alga, were used as the food in coprophagy.

Nereis is extremely efficient in its assimilation of dietary lipids and produces faeces with very low fatty acid:sterol (FAST) ratios in both herbivory and coprophagy. The net decrease in total lipid in both modes of feeding with this species suggests that annelids, where present, are as important as other invertebrate groups in affecting the flux of lipids through marine food chains.

Juvenile and adult two-spot gobies, Gobiusculus flavescens (Fabricius), were collected at three sites in the Plymouth area: the Plymouth Breakwater, Fort Bovisand, and the Yealm estuary. Fish were sampled by a diver-held grab-net, boat-towed zooplankton net, and beam-trawl, from early June until the end of September 1987.

Percentage abundance and percentage occurrence dietary data are presented by a graphical technique, such that prey importance (rare or dominant) and fish feeding strategy (specialist or generalist), is visually apparent. It is applied to the different size groups of fish from each site.

Gastropod shells are essential to most hermit crabs. Shell availability limits hermit crab populations. Shells provide protection and the degree of shell-fit controls crab growth and fecundity. Crabs locate new gastropod shells from a distance under water by molecules released from gastropod flesh during predation events. Here we test the hypothesis that the salivary glands of the predatory gastropod are the source of enzymes that digest muscle proteins and release peptide attractants. We describe the anatomy of both the acinous salivary glands and the tubular accessory salivary glands of Busycon contrarium which are similar to those of B. carica. The salivary gland ducts empty at the mouth, suggesting a role in the primary digestion of food. We show that gastropod muscle proteins, extracted by salt solutions with the ionic strength of sea water and purified by precipitation in low ionic strength can be digested by gastropod salivary gland enzymes to generate peptides attractive to the hermit crab, Clibanarius vittatus, in field assays.

The population structure of the common shrimp Crangon crangon (L.) in British waters is investigated. Samples were collected from 31 sites along the coasts of England, Wales, Holland, Belgium and France. Using a morphometric analysis it is concluded that English and Welsh waters hold six distinct populations. Animals belonging to the same population are found on the opposing English and continental coasts in the southern North Sea and English Channel which indicates that the avoidance of offshore waters is not isolating the shrimps. The boundaries between the populations are found to correspond with the boundaries between major plankton assemblages. It is suggested that the populations are isolated by the reduced dispersal of the planktonic larvae across fronts where bodies of water with different physical properties meet but incompletely mix.

The mobility and quantity of retinula cell proximal screening pigment, and the liability of the eyes to light-induced damage, were investigated in the Norway lobster, Nephrops norvegicus (L.), obtained from three separate populations from depths of 18, 75, and 135 m.

During the morning after capture, the migration of the proximal pigment in response to the onset of illumination below the threshold for damage varied between the three populations. In the eyes of deep water N. norvegicus, the proximal screening pigment was located close to or below the basement membrane when dark-adapted and rose to a position midway up the rhabdoms when light-adapted. In the dark-adapted N. norvegicus from shallow water the proximal pigment was located more distally than in eyes of deep water animals. After the onset of illumination, the pigment migrated distally to completely cover the rhabdoms. The amount of retinula cell proximal screening pigment was found to decrease linearly with depth.

When dark-adapted individuals from each depth were exposed to light a positive correlation was obtained between the photon fluence rate (PER) and the proportion of the retina damaged. For a given light exposure the amount of damage was highest in animals from deeper water. The PFR causing 25% damage was approximately 1 log unit higher in animals from 18 m compared to those from 135 m.

The amount of damage varied with the delay between capture of the animals and exposure to light. When exposed 2 h after capture significant differences between depths were seen but the results were influenced by the incomplete dark adaptation of some specimens.

The influence of photoperiodicity on hatching of Loligo forbesi and Loligo vulgaris embryos was investigated under different experimental light-dark (LD) conditions. The transition from light to dark stimulated hatching and functions as a ‘Zeitgeber’ or synchronizer. Independent of the timing and duration of the dark period most embryos hatched soon after termination of the light period. Embryos which had developed in constant light, showed no hatching rhythm at all. If these embryos were exposed to a dark shock most embryos hatched soon after the onset of darkness. A twilight shock, in which the light was reduced by 50% (i.e. 50 μE s−1 m−2), could not stimulate hatching. Embryos which were kept from stage X on in an artificially controlled LD cycle, preferentially hatch in a period which coincides with the period at which darkness usually occurred when placed in constant illumination from stage XX onwards.

Differences in average body size among allopatric and sympatric populations of hydrobiid mudsnails have been interpreted as the consequence of interspecific competitive interactions. Recently, however, doubts have been expressed concerning the certainty with which size differences can be ascribed simply to character displacement. Other environmental factors are known to influence body size in hydrobiids. In the present study one of these, sediment type, was investigated.

Average body weight of Hydrobia ulvae (Pennant) living on fine mud was consistently higher than that of members of the same species living on adjacent muddy sand. Snails were transplanted from one sediment type to the other, confined within cages, and their growth rates compared with those of control animals caged on their native sediment. The results of this experiment suggested that substrate type is one factor controlling body size, but the inconclusive nature of the results indicate that others are also involved.

Field and experimental observations on sea anemones (Actinaria) Ammonia viridis (Forskål) and Actinia equina (L.) indicated that in both species body zinc concentrations usually ranged between 100 and 200 ug (g dry wt)1 in waters containing up to 200 μg I1 of the metal. At higher dissolved concentrations, as observed in Restronguet Creek, A. equina exhibited only slightly enhanced tissue levels. However, in the laboratory, zinc levels in Anemonia viridis increased markedly at sea-water concentrations exceeding 200 μg I”1. Studies on the uptake of 65Zn-labelled zinc showed that, when the sea-water concentration was increased from 2 to 52 μg 11, both species absorbed the metal and new equilibria appeared to be reached in about a week. At equilibrium, the concentration of zinc in Actinia equina had risen by up to 11%, and in Anemon ia viridis, by up to 28%. About one third of the difference between the amounts absorbed by the two species may be accounted for by zinc accumulated in the symbiotic algae (zooxanthellae) of A. viridis. Short-term (12 h) experiments showed that, although A. viridis absorbed a significant amount of labelled zinc when the concentration increased from 2 to 52 μg I1, uptake was not much greater when the concentration increased from 2 to 202 μg I1. It is postulated that, up to a sea-water concentration of 202 μg I1, the absorption of zinc is dependent on the amount adsorbed at the body surface: saturation of the surface at higher concentrations leads to more direct dependence on the level of dissolved zinc.