The escal light gland of three different-sized specimens of the deep-sea anglerfish Haplophryne mollis (family Linophrynidae) has been examined by light and electron microscopy. The light gland has a central cavity, with diverging branched ducts which ramify into numerous tightly-packed radial tubules. In the two largest specimens all glandular lumina contain symbiotic bacteria. Except for a thin-walled part of the typical radiating tubules, the epithelial walls of the light gland are of a uniform structure, consisting of flattened basal cells, situated next to the basal lamina, and tall cells extending to the lumen.

In the smallest specimen examined the various parts of the light gland were not fully differentiated and only a very few symbiotic bacteria were present; its glandular epithelium differed from that of the two larger specimens by containing many goblet cells, the secretion of which may be important for the initial establishment of the right strain of symbiotic bacteria

Observations on the luminescence of live specimens have shown that the light emission can be rapidly modulated from within the esca. The in vivo flash kinetics are considerably slower than those of Dolopichthys longicornis, but similar to those of both the caruncle exudate of Ceratias holboelli and in vitro anglerfish bacterial luciferase.

Through SEM observations a probable sense organ located at the base of the ventral side of each dorsal cirrus in some eunicid polychaetes is described. This organ is externally characterized by numerous long ciliary projections. Similar structures are also found on corresponding positions in species belonging to other family groups in the Order Eunicida but in the Order Phyllodocida were found only in Aglaophamus sp. This species also has a similar structure, with ciliary projections, at the ventral base of each dorsal cirrus. However, the situation is quite different from any Eunicida species in that numerous bundles of ciliary projections are also scattered on the lateral sides of the body. Although the function of the ciliated organ of eunicids still remains unknown, a brief TEM observation of this organ on Marphysa sanguinea clearly shows that this organ is a sensory receptor and seems to suggest that it serves as a chemoreceptor rather than a mechanoreceptor.

Gill number 8 of intermoult male Carcinus maenas (L.) (Decapoda: Brachyura) was used to study the morphological variation and distribution of the major gill cells. Three gill regions (proximal, mid and distal) were sectioned and examined by light and transmission electron microscopy. The ultrastructure of the three epithelial cell types (striated, chief and pillar) was similar to previously published descriptions, but some variations in cell form and distribution were observed. In all gill regions, striated and chief cells were larger towards the lamellar raphe than near the marginal canal. In the proximal gill region, the epithelium consisted almost exclusively of striated cells, implying an osmotic/ionic role for this region. In the mid gill region, the epithelium comprised a mixture of chief and striated cells. In the distal region, chief cells predominated, implying a respiratory role for this region. Pillar cells exhibited no clear distributional pattern within the gill and, although their shape varied with position, their involvement in ionic regulation, osmoregulation, respiration, structural support or the flow of haemolymph through the gill is not clearly defined. Nephrocytes, thought to be involved in gill defence mechanisms, occurred in the haemolymph space or attached to the intralamellar septum and showed no structural variability. Glycocytes were always associated with the intralamellar septum, implying that there are specific gill regions for glycogen storage. Haemocytes showed some structural variation but there was no obvious correlation with gill region; small-granule haemocytes were the most common haemocyte type in the gill.

The membranous lobe of Thenus orientalis (Lund) is a broad fleshy protuberance arising midventrally from the sternal skeleton between the second maxillipeds. Its position, morphology and structure are described and its association with the metastome of other crustaceans discussed. Several roles during ingestion can be postulated. The lobe extends anteriorly towards the mandibles and forms the roof of the preoral cavity and posterior boundary of the mouth. It has a flattened strengthening rod extending the width of the aboral surface, which is covered by three types of anteriorly-directed annulate setae and densely arranged clusters of microscales and microspines. Histologically it is characterized by large amounts of longitudinal and circular striated muscle and tegumental glands beneath the oral surface. These glands secrete sulphated acidic mucopolysaccharides which lubricate food during ingestion. Spherical cells are dispersed throughout the connective tissue beneath the aboral surface. These are characterized by a granular homogeneous cytoplasm, a peripheral cell nucleus and few organelles. Their contents stain positively for protein and neutral mucopolysaccharides and their role is most likely storage of these compounds, although the significance of this is not known. During ingestion, food is passed over the lobe surface and its anterior lip retracts ventro-posteriorly, dilating the preoral cavity to allow quick and efficient swallowing of large food items.

The functional morphology of the buccal mass of 23 species of cephalopod (Octopoda, 4 species; Teuthoidea, 17; Sepioidea, 2) was investigated by gross dissection, histology and observations on fresh preparations. Cephalopod beaks lack a joint or articulation point. The jaws slide and rotate around an area rather than a fixed point. During closing the superior mandibular muscle (SMM) provides the force of a bite and the largest movement vector, whilst the inferior mandibular muscle (IMM) acts to retract the upper beak, causing shearing action. Dorsal portions of the lateral mandibular muscles (LMM) flex the upper beak walls outwards, probably to accommodate the backwards sweep of the radula and buccal palps during closing. To open the beaks, the ventral portions of the lateral mandibular muscles pull the rear lateral walls of the two beaks towards each other, moving the lower beak back relative to the upper.

The antifouling performance of the dogfish Scyliorhinus canicula (L.) (Elasmobranchii: Squaliformes) eggcase-embryo combination was studied under experimental conditions, in conjunction with an analysis of fouling on wild cases. The cases were shown to develop an external heterogeneous microbial biofilm, and an internal heterogeneous microbial biofilm (when the case opens) composed primarily of cocci and bacilli. Macrofouling was limited on egg-cases (unless kept under high light intensities). Macrofouling ranged from <5% (recently laid cases) to 42% (>300 days exposure). This is a better performance than many commercial antifouling treatments. There was no evidence that the embryo was involved in the antifouling process. A priori, three hypotheses are suggested that might explain the antifouling mechanism of the dogfish eggcase-embryo combination: (1) the yolk/albumin/embryo emit antifouling chemicals; (2) a bacterial culture develops that prevents further fouling; (3) the case with/without an embryo has antifouling properties. The results presented here support the third hypothesis.

The incidental capture of sharks in the bottom-set gill-net fishery off the south coast of Ireland was quantified by placing observers on commercial gill-netters for the duration of a fishing trip. Forty fishing trips were sampled resulting in 1,167 km and 19,760 km h of observed fishing effort. Sixty individual sharks of seven species were reported entangled in the fishing gear. Tope, porbeagle and six-gilled sharks were the most frequently caught species, with black-mouthed dogfish, blue shark, basking shark and starry smooth hound also recorded. Total fishing effort along the south coast was calculated and total capture extrapolated from observed catch rates. An estimated 6,000 sharks were caught in this fishery during the study period.

The in situ growth rates of marine planktonic ciliates from Plymouth Sound were determined after fractionating the natural community into several size categories to remove predators of different sizes. Total community in situ growth rates varied from 0·01 to 0·57 d−1 according to fractionation treatment, with the four most abundant taxa, comprising three species of Strombidium, and Mesodinium rubrum, achieving maximum in situ growth rates of between 0·41 and 0·68 d−1. These values are approximately half the maximum theoretical rates calculated indirectly using an equation which relates ciliate growth to cell size and temperature. Given the conservative nature of in situ growth rate measurements, the growth rates reported here appear appropriate for a natural ciliate community growing within a nutritionally favourable environment.

Two erect species of bryozoans, Alloeflustra tenuis (Kluge) and Nematoflustra flagellata (Waters), occur abundantly in similar localities at Signy Island, Antarctica. Both species are unilaminar and are colonized by a range of epibiotic taxa, principally other cheilostome bryozoans. A detailed study was undertaken of the bryozoan epibiota of these two species, collected by SCUBA over the depth range 36 to 40 m. The degree of colonization varied with host size and differed between the front and rear surfaces of each host species, and between host species. The species composition of the epibiota was also different between species and between surfaces within species. These variations are possibly related to differences between the host species in the abundance, structure and function of avicularia (putative protective structures). Specimens from deeper water (150 m) showed significantly reduced colonization by epibiota, but the same overall patterns of colonization between the two species and surfaces were still observed.

The species composition, abundance and spatial distribution of macroplanktonic cnidarians in the eastern part of the Weddell Gyre are described from a series of nekton samples collected over three depth ranges between 0 and 2000 m. On average, cnidarians contributed 52·6% to the biovolume of these samples, although the range was high (5·0–93·1%). In total 23 species of siphonophores and 20 species of medusae were identified; a number that is very high in comparison with previous studies. There was a high diversity at bathypelagic depths, with 38 species being collected below 1000 m. The most abundant siphonophores were Dimophyes arctica (up to 45 nectophores per 104 m3) and Heteropyramis crystallina (up to 22 nectophores per 104 m3). The most abundant medusa was Pantachogon haeckeli (up to 30 specimens per 104 m3). Medusae were most abundant at mesopelagic depths, reaching 46 specimens per 104 m3 in the 500–1000 m depth range. Smaller calycophoran siphonophores were concentrated in the top 500 m of the water column, with total numbers averaging 107 per 104 m3. The number of larger calycophorans in-creased with depth, being most abundant in the 1000–2000 m depth range. Although many species had a widespread geographical distribution within the sampling area, the hydrographical conditions appeared to be affecting the distribution of some.

Samples of the large sublittoral sea anemone Urticina eques (Gosse) were collected from three localities in the northern North Sea and from one locality in the northern Irish Sea. Around the coast the total distance between sampling sites is approximately 1,200 km. The species has a large lecithotrophic larva which may not be planktonic. All samples were screened genetically for 13 loci coding for 11 different enzymes. Results overall indicated a high degree of genetic uniformity over the four populations sampled (FST = 0·025). The data are discussed in relation to current ideas of larval dispersal and results from other similar studies. It is concluded that the lack of genetic differentiation shown by Urticina eques is surprising given the apparently poor dispersive powers of the larva.

Perinereis nuntia brevicirrus (Grube 1857), collected from a rocky shore at Qingdao (China) were cultured under different temperature, daylength and moonlight regimes. Ripe individuals were found in the field after an increase of water temperature in early summer, with a semilunar spawning peak from the beginning of June to the end of September. In laboratory experiments, daylength has no influence on maturation and reproduction. Temperature-controlled culture produces gravid, reproducing specimens at any time of the year after an increase in water temperature. For reproduction both sexual partners leave their burrows and swarm at the water surface in the early morning, performing a nuptial dance. The spawning behaviour, the nuptial dance and the release of gametes, are controlled by sex pheromones which are present in the coelomic fluid of mature worms. A sex pheromone from Platynereis dumerilü, 5-methyl-3-heptanone, is found in Perinereis nuntia brevicirrus and causes an increase in swimming activity during reproduction and the release of a small amount of sperm from males. This signal induces the release of eggs by the females followed by the release of masses of sperm by the male due to a second female pheromone.

On an intertidal mud flat in the Ria Formosa (southern Portugal) Abra ovata (Mollusca: Bivalvia) showed effective meiobenthic and macrobenthic dispersal (i.e. of individuals smaller and larger than 1 mm). This was important to compensate for mortality caused by shore crabs during summer. It was observed in the laboratory that A. ovata deposited eggs in capsules on the sediment surface; after 11–15 d at 20°C benthic juveniles of 210–220 (im shell length hatched from these capsules. A pelagic larval stage was missing. Large numbers of specimens of about 1 mm shell length colonized protected buckets between February and June.

Shell growth of the razor clam Ensis siliqua (Mollusca: Bivalvia) from southern Portugal has been analysed using both surface growth rings and internal shell microgrowth patterns. The growth rate estimated from an analysis of the growth rings is slower (von Bertalanffy growth, constant K=0·27) than that determined from the annual narrowing of the internal microgrowth patterns present in shell sections (K=0·65), although both methods predict a similar asymptotic length, L∞, of 144·8 and 139·6 mm, respectively.

The Barrinha razor clam population occurs in a heavily dredged area and an analysis of shell sections reveals the presence of a series of shell margin breaks consisting of deep clefts in the outer shell layer in which sand grains are embedded. It is suggested that these disturbances to shell growth are the result of repeated dredge damage. The frequency of the clefts increases with the size and age of the razor clams, and thus the shells provide a record of the intensity and frequency of unsuccessful capture or retrieval attempts. Cleft formation also occurred seasonally with the deposition of a small cleft during June, but these annual clefts were much less pronounced than those caused by dredge damage.

Two razor clam populations from two shores in North Wales were identified on morphological grounds as Ensis siliqua (L.) and E. ensis (L.). Ensis siliqua occurs in fine sand on the exposed south-westerly facing shore of Newborough beach, whilst E. ensis inhabits the coarser sediment of Penmon beach, a sheltered north-easterly facing shore in the Menai Strait. At Penmon smaller E. ensis (<100 mm) inhabited sediments at mean low water of spring fides, whereas larger individuals (>100 mm) occurred almost subtidally at extreme low water springs. No small E. siliqua (<110 mm) were found on Newborough beach, where there has been a noticeable decline between 1990 and 1992 in the number of individuals larger than 175 mm. Growth of the two species was different. The von Bertalanffy growth constant, k, was similar in the two species, but E. siliqua had a larger asymptotic length than E. ensis.

Laboratory-reared herring larvae adjusted several characteristics of their swimming behaviour to the presence of food in the experimental tank. When food density was low, as in the outer limits of a food patch in the sea, the larvae increased their turning frequency, an exploratory behaviour to locate the centre of the patch. At a higher prey concentration, such as in the centre of a food patch, the larvae crossed their previous swimming path more frequently, indicating a local search strategy aimed at foraging in the centre of the patch.

The prey of actively foraging planktonic predators, such as fish larvae, is patchily distributed. The main factors governing the ability of the predators to encounter prey are the relative velocities of predator and prey, and the prey detection radius by the predator relative to the distance between prey items (Gerritsen & Strickler, 1977). The enhancement of encounter rate by turbulence through its effect on relative velocity has been widely discussed in the literature since Rothschild & Osborn's (1988) publication. However, an effective forager should be able to adjust its behaviour to optimize prey encounter by, for example, altering its position in the water column in relation to conditions of turbulence, or modifying its searching behaviour in response to spatial aggregation of prey. This latter aspect has received comparatively little attention. Different swimming modes have been described in herring (Clupea harengus L.) larvae and in larvae of many other fish species. Foraging larvae swim in a more linear path between food patches and follow a more complex track when a patch of prey is located.

Ligia italica Fabricius is a day-active isopod on the shores of Madeira. The population migrates up and down the shore with the tide, browsing on lichens and macroalgae. Shore bird predation is negligible; foraging wall lizards are the only daytime predators. Ligia italica retreats into crevices at night. It exploits plant material within supralittoral and intertidal pools and enters pools with salinities as high as 74‰. Ligia italica emerges from pools at intervals to breathe in air; such emersion lasts no more than two minutes. Ligia italica on Madeira has no colour change ability, the isopods remaining dark grey/black whatever the background.

The echiuran worm Thalassema thalassemum (Echiura: Echiuridae), is a deposit-feeder which uses its proboscis to collect sediment particles for ingestion. The proboscis is highly extensible and is used with dorsal surface downwards to skim particles from the sediment surface. Alternatively, the distal portion of the proboscis is arched over and the ventral surface of the tip is held against the sediment surface where ciliary movement facilitates particle collection. These methods are used in combination and collected material is moved back along the proboscis, the edges of which are rolled to form a closed tube. Burrows appear to be U-shaped with one predominantly inhalant and one exhalant opening. Faecal pellets are periodically ejected forming small mounds around exhalant openings and mean rates of 1·83 and 2·80 g dry wt d−1 were measured suggesting that, in sufficient densities, this species could make a significant contribution to macrofaunal bioturbation.

Despite extensive studies on settlement of the cypris larva of Balanus amphitrite amphitrite Darwin (Crustacea: Cirripedia), the fine structure of the putative settlement receptors of this species has not been described. This study presents observations made with the scanning electron microscope of the fourth antennular segment and its associated setae.

Juvenile mussels (Mytilus edulis, Mollusca: Bivalvia) were subjected to a simple assay to investigate the pattern and timing of the shift from high copper resistance of the veliger larva to the lower resistance of the adult. The level of resistance found in veligers persists in mussels of 1 mm shell length (400 ppb Cu; LT50, 12.5 d) while the lower adult level of resistance is reached at a shell length of 5 mm (400 ppb Cu; LT50 2.8–5.3 d). Resistance declines gradually, being significantly correlated with shell length (P<0.02) such that size differences explain 88% of the variation in copper resistance among juvenile mussels.