A survey of benthic communities found in a heavily fished scallop ground was undertaken in July 1993. Two main faunal assemblages were identified from samples obtained with fine-meshed scallop dredges, which were grouped either in gravelly sand sediments or sandy sediment, which was generally furthest offshore in deeper water. A third assemblage was found in either sandy or gravelly muddy sand sediments. The highest abundance of small and large size-classes of scallops were associated with the assemblage containing the greatest number of species and individuals in sandy sediments. This assemblage had the greatest biomass of emergent fauna such as hydroids and Alcyonium digitatum. Data acquired from a RoxAnn™ acoustic signal processor were able to differentiate between the substratum or biotopes associated with the greatest abundance of scallops. This may provide a useful tool for refining surveys of commercial stocks or mapping suitable habitats.

Underwater television observations were made of mobile macrofauna inhabiting two parts of a sublittoral reef on the west coast of Scotland for 48 h periods in spring, summer, autumn and winter. Continuous occurrence profiles (mean hourly frequency of occurrence, %) were detailed for 12 species of fish (Chirolophis ascanii, Conger conger, Ctenolabrus rupestris, Lepadogaster candollei, Myoxocephalus scorpius, Pholis gunnellus, Pollachius pollachius, Raniceps raninus, Phrynorhombus regius, Zeugopterus punctatus, Thorogobius ephippiatus and Trisopterus minutus), ten crustacean species (Cancer pagurus, Carcinus maenas, Galathea strigosa, Homarus gammarus, Inachus spp., Munida rugosa, Necora puber, Brachyuran sp., Caridean sp. and Pagurid sp.) and four echinoderm species (Antedon bifida, Asterias rubens, Hemicia oculata and Solaster endeca). Rhythmic patterns of diel activity and/or occurrence were identified for several species. Chirolophis ascanii, Ctenolabrus rupestris, L. candollei, Myoxocephalus scorpius, Pholis gunnellus, Pollachius pollachius, Thorogobius ephippiatus, Trisopterus minutus and Munida rugosa were predominantly diurnal, but Ctenolabrus rupestris, Myoxocephalus scorpius and Trisopterus minutus also showed some evidence of crepuscular activity. Raniceps raninus activity was predominantly nocturnal but became continuous in summer. In other species (the topknots Phrynorhombus regius and Z. punctatus and the crustaceans Cancer pagurus and Homarus gammarus) identifiable occurrence patterns changed with season or site. The greatest number of fish species occurred in winter with Myoxocephalus scorpius, Pollachius pollachius and topknots (Phrynorhombus regius and Z. punctatus) showing greater occurrence/activity during spring and winter. Co-occurrence analysis was used to identify species interactions or avoidances.

A new species of sponge: Higginsia ciccaresei sp. nov. (Demospongiae: Desmoxyidae) is described from a marine cave of the Ionian Apulian coast (Mediterranean Sea). It lives in complete darkness, 250 m from the cave entrance, in a basin of anchialine waters of low salinity and relatively cool temperature. The spicule formation process seems to be affected by some of the peculiar characteristics of the ambient water, resulting in spicules of unusual shape and irregular surface. This is the second record of the genus Higginsia – which has a world-wide distribution – from the Mediterranean Sea. The hypothesis that H. ciccaresei could be considered as a tethyan relic which survived in the peculiar habitat of an anchialine cave is also suggested.

Sixteen sponge species were recorded from Little Letite Passage, an area of highvelocity tidal currents located in the Bay of Fundy near Deer Island, New Brunswick, Canada. Of these 16 species, four species (Myxilla fimbriata, Hymeniacidon heliophila, Hemigellius sp. aff. flagellifer, and Crella rosea) have not previously been recorded from the Bay of Fundy. One new species, Hymedesmia canadensis, is described, based on the presence of a second peculiar chelate microsclere added to the spicule armament.

The genus Podocoryna is characterized by species living on shells usually inhabited by hermit crabs; but the mutual benefits of this association are not well understood.

This study, besides describing the biological cycle of the hydroid Podocoryna exigua, brings new information on the relationship between hydroid and the hermit crab Diogenes pugilator, especially concerning their trophic strategies.

The hydroid shows a seasonal cycle with a minimum density during summer and an increase during autumn and winter, reaching the highest value in spring. The production of medusae is almost constant during all seasons. The dwelling behaviour of the hermit crab affects a particular sedimentivorous strategy of the polyps while a clepto-commensalistic strategy is adopted by the hermit crab towards the hydroid. Laboratory experiments show that the presence/absence of the hermit crab in the shell and also the seawater temperature strongly influence the number of spines, particularly structures developing from polyps. In addition, free-living polyps in the sediments may represent a strategy to colonize free shells.

Consistent with most other closely-related polychaete species which have been analysed cytogenetically to-date, Pomatoceros triqueter and P. lamarckii share an identical chromosome number (2n=24) and have a number of other karyotypic features in common. However, commensurate with their separate species status, their karyotypes differ at least in four chromosome positions as a result of structural chromosomal rearrangements. With a rDNA probe using the FISH technique, we have been able to demonstrate that the nucleolar organizer region (NOR) occurs at the same site on the same pair of chromosomes in the two species, which indicates that an inversion event is unlikely to have been the cause of the species variation in this particular case. Taken together, these karyotypic differences may be indicative of a chromosomal barrier to the formation of fertile offspring; an important feature for maintaining species integrity where the two forms occur sympatrically, such as in parts of south-west England.

The variability in the number of segments in anterior (A) and median (B) regions of adult-size specimens Spiochaetopterus solitarius (Chaetopteridae), was examined in the present study. Variability of region A is considered in relation to the number of specialized setae in A4, which varies from 2 to 4; variability of region B is observed as a decrease in the number of segments during a limited part of the year. A process involving autotomy and regeneration has been advanced to explain the variability in the number of segments in region B. It appears that, once the number of segments in region B reaches a certain level, which is close to 30, the animal divides within region B, and the missing parts of each section are then regenerated. The maximum number of segments in region B may be considered to be species specific and used as a discriminative feature in the genus. It is suggested that regeneration does not reflect asexual multiplication per se, but provides a means to facilitate the supply of energy to region B, which is responsible for bringing the products of the sexual organs to maturity. Consequently, regeneration is considered to complement sexual reproduction, facilitating the availability of energy to region B for reproduction. Implications of this variability have been examined by comparing S. solitarius and S. costarum, two species closely related by their morphology, sympatry and syntopy.

Studies of the osmotic and ionic responses of the supralittoral rock pool inhabitant Tigriopus brevicornis (Crustacea: Copepoda) showed that this species of orange harpacticoid copepod is an unusually euryhaline osmoconformer. Body fluid osmolalities were 297–3691 mOsm kg−1 over a medium range of 151–3440 mOsm kg−1. Whole body sodium increased from 3·65 to 15·0 μmol Na+ mg DW−1 (dry weight) over the medium range 80–1900 mM Na+. Comparative studies on Artemia nauplii and the prawn Palaemon elegans revealed the characteristic hyper-hyporegulation of both organisms. Body density of T. brevicornis remains greater than that of the external medium over the salinity range 5–100 psu because of changes in body fluid osmolality and body volume. Median body density values for T. brevicornis ranged from 1·0359 g ml−1 in 5 psu (median density of 5psu seawater–1·0017 g ml−1) to 1·0848 g ml−1 in 100 psu (median density of 100 psu seawater=1·0751 g ml−1). Tigriopus brevicornis is principally a benthic forager and needs to remain negatively buoyant over a wide salinity range. Environmental monitoring of five supralittoral rockpools was conducted over a year. Live or dormant T. brevicornis were found in salinities of 4–150 psu; temperatures of −1 to +32°C and oxygen concentrations of 0 to >20 mg l−1. It is probably of advantage to T. brevicornis to be an osmoconformer; it is perhaps energetically efficient for such a small organism (~1 mm) and avoids buoyancy problems at high salinity.

The chronometric mechanism of compensation for the apparent movement of the sun was investigated in adult individuals of Talitrus saltator (Amphipoda: Talitridae) from Mediterranean latitudes. The individuals were subjected to alteration of the duration of illumination, while its phase remained the same as in nature. A close relation between photoperiod length and the chronometric mechanism of the sun compass was observed, which could explain the seasonal adaptation of the sun compass. We propose an alternative to the classic hypothesis of daily differential compensation for the apparent movement of the sun.

A Corophium-bed characterized by a mosaic of emerged areas and tidal pools during low water was established on an intertidal flat in the southern part of the Danish Wadden Sea. In spring 1990, the plateaux harboured relatively high densities of the amphipod Corophium volutator, whereas the amphipods were almost absent in the pools. Following a parasite-induced mass-mortality in the population of Corophium, summer 1990, the plateaux of the bed were subjected to sediment erosion. The heterogeneous plateau-pool structure disappeared, accompanied by increased median particle diameter and decreased silt content in the former plateau sediment. These events were accompanied by increased chlorophyll-a concentrations in the sediment of both plateau and pool areas.

The results suggest Corophium volutator to be the single most important organism stabilizing the plateau sediment, and hence, the heterogeneous topographic structure of the Corophium-bed. It is proposed that the stabilizing effect of Corophium burrows also in deeper sediment strata may outweigh the surface stabilizing influence of epipelic diatoms, as well as the negative effect of amphipods eating the diatoms, in non-cohesive coarser sediments.

One hundred and ninety-eight suprabenthic hauls from the English Channel and the Seine Estuary were taken with a modified Macer-GIROQ sledge. Numerically, mysids were the dominant group amongst the peracarids collected with the sledge and 28 species were recorded. Mysid densities were higher in the oligohaline zone (>200,000 ind 100 m-3) of the Seine Estuary than at other stations in the English Channel (where the density was the highest on medium sand stations, ~5000 ind 100 m-3). Two main gradients of mysid distribution were identified: (1) a higher species richness in the western part of the Channel compared with the eastern part of the Channel; and (2) an increasing density gradient from west to east during spring and a decreasing gradient from west to east during the autumn (eastern high abundance of Haplostylus spp. during spring, and western high abundance of Schistomysis ornata and Erythrops elegans during autumn). Mysids showed important diel rhythms with maximum abundance at sunrise and sunset, and low density at night. According to their swimming activities, suprabenthic mysids were classified into three groups: upper organisms with a very strong activity, species with a strong activity and occupying the whole water column near the sea-floor, and lower species with limited swimming activity. Nevertheless, the swimming activity could be modified according to the hydrodynamics of each site. A seasonal cycle of abundance (summer recruitment for dominant species Anchialina agilis, Haplostylus lobatus, Haplostylus normani) was observed on two stations where temporal samples along the year were available.

The cirral activity of the whale barnacle Cryptolepas rhachianechi was studied in a flow tank at different flow regimes. In still water, unidirectional flow, and oscillating flow, the cirral fans of adult animals always beat in the direction of the rostrum. Adults did not respond to water current from the carinal direction by facing the cirral fan into the current; however, during copulation they could turn the cirral fan so it faces the carina. Newly settled animals responded to flow from the carinal direction and to oscillating flow by facing their cirral fans towards the oncoming current, but there is no synchronization between changes in water flow direction and the change in cirral direction. Since these barnacles are normally exposed only to unidirectional currents, with no need to respond to flow from the carinal direction or to oscillating flow, it seems likely that they have lost the ability to change the direction of their cirral beats. This loss of the ability to respond to changes in current direction is a specialization of C. rhachianechi related to its epizoic mode of life.

Eriocheir sinensis, the Chinese mitten crab, is a native of east Asia and predominantly lives in freshwater but migrates seawards to breed. In 1912 a specimen was collected in the River Aller, a tributary of the Weser, Germany and now this exotic species has a European distribution from Finland to the Atlantic coast of southern France. In the UK, the mitten crab has been reported from the Humber, Medway and Thames catchments. Although the population in Thames had remained low, recent evidence suggests it is increasing, which has potential environmental implications.

The prosobranch limpet Patella vulgata is an intertidal grazer performing looped excursions centred on a home scar. Foraging within each excursion is mostly concentrated around the point of maximum distance from home. The orientation of the foraging excursions in a group of limpets was analysed on a vertical substrate on a sheltered shore in North Wales. The spatial relationship between different excursions of the same individual was also analysed. A total of 174 complete excursions from 47 adult limpets were obtained using the LED (light emitting diode) tracking technique. In particular, the leaving direction and the direction of the main foraging area of each excursion were computed. When considering the foraging strategy over five consecutive days, a substantially radial cropping pattern was evident at both the population and individual level, with no evident directional preference. However, when considering consecutive excursions of the same individual a concordance in leaving directions was evident in about 40% of cases. The high overlap between the outward branch of the trajectory of one night and the homing branch of the previous one suggests that the directional decision can be based on a trail-following mechanism. Moreover, our data suggest that directional decisions are taken at the beginning of each excursion when leaving home.

The reproductive cycle of Nassarius (Hinia) reticulatus was investigated in the Ria de Aveiro on the north-west Portuguese coast during 1992 and 1993. A clear seasonal pattern was observed with the beginning of gametogenesis in August followed by ripening of the gonads in January and February and spawning from February to July. The increase of water temperature above 11°C in February 1993 was associated presumably with the release of gametes. Recruitment inside the Ria of juveniles with 6·5 mm mean shell height was detected in February 1993 and these individuals were spawned in the previous year. Males of N. reticulatus exhibited a considerable variation in length of the penis throughout the reproductive cycle. The accuracy of the use of relative penis length (RPL) index for intersite comparisons of imposex is discussed and the magnitude of the error that might be involved when comparisons are made using populations in different phases of the reproductive cycle is evaluated.

Annual reproductive cycles of two commercially important bivalves, the razor clam Ensis siliqua and the clam Venus striatula were investigated. Specimens of both species were sampled monthly from a site off Vilamoura, south of Portugal, between June 1992 and May 1993. Gonadal development was monitored using standard histological methods. Observed gametogenic progression was categorized by six stages: (0) inactive; (I) early active gametogenesis; (II) late active gametogenesis; (HI) ripe; (IV) partially spawned; and (V) spent. Both males and females showed a synchronism in gonadal development. The gametogenesis in the razor clam began in December and by late April the gonads were characterized morphologically by an abundance of ripe eggs and sperm. Partially spawned individuals were first encountered in May. All were spent by July. The gametogenic activity in V. striatula began in the months of October/November and continued until March. Spawning occurred between April and early August. Both species reached maturity during the first year of life.

This paper gives morphometric variations and dorsal mantle length–total weight (DML-TW) relationships for Illex coindetii in the eastern Central Atlantic area. Positive allometry was observed in males and negative in females of the species. The most variable body measurements between males and females were width and perimeter of the head. In the study area, divergence of morphometric measurement starts at 95 mm. The point of divergence, however, varies with latitude; fluctuating from 104 mm in the north (Morocco and Sahara) to 76 mm in the central area (Mauritania and north of Senegal) and 73 mm in the south (Gulf of Guinea).

The relationships between DML and TW showed that sexual dimorphism due to differential growth between males and females starts to occur at 56 mm ML. The starting point of sexual dimorphism (56 mm) varies according to the zone; the higher the latitude, the later it occurs. Thus, sexual dimorphism occurs at 49 mm in the south (Gulf of Guinea), at 54 mm in the central area (Mauritania and north of Senegal) and at 74 mm in the north (Morocco and Sahara). Females grow larger than males, but males were heavier at any given length. As latitude decreased, a slow down in the increase in weight-at-length was observed in both sexes.

This study provides the first quantitative description of the emetic reflex (vomiting) in the dogfish (Scyliorhinus canicula) by using veratrine HC1 (lOmgkg−1, i.p.), the sodium channel activator as a stimulus. Vomiting occurred within 10 min of injection. The most notable features of the response in the correct temporal sequence were: (i) head shaking with wide gaping of the mouth; (ii) lowering of the ventral buccal cavity and expansion of the pharyngeal cavity; (iii) contraction of the gill arches, the buccopharyngeal musculature and lowering of the jaw rapidly followed by the expulsion of gastric contents (pieces of fish). The expulsion sequence (ii and iii) took ~ 1 s. The significance of the vomiting reflex in the dogfish is discussed in terms of its protective function and as a component of normal feeding to periodically eject indigestible food residues.

The ontogeny of evasive behaviours was examined in Atlantic menhaden (Brevoortia tyrannus, Clupeidae) and bay anchovy (Anchoa mitchilli, Engraulidae), with supplemental data for scaled sardine (Harengula jaguana, Clupeidae). Predicted relationships between ecology and behavioural ontogeny were tested using the different patterns of inshore vs offshore habitat utilization displayed by these species. In two of the species, menhaden and anchovy, the roles of vision, mechanoreception, and audition in evasive behaviours were examined ontogenetically and compared to the morphological development of these sensory systems. Anchovy early larvae were more responsive to a predatory stimulus than were menhaden; sardine early larvae were intermediate in responsiveness. By the end of the larval period most individuals tested in all three species responded. These results matched the pattern predicted by larval habitat. Ontogenetic trends in reactive distance did not match predictions based on habitat for these species but instead appeared to be more dependent upon changes in sensory morphology. In menhaden, ontogenetic changes in responsiveness were more dependent upon neuromast proliferation and cephalic lateral-line canal formation, while in anchovy these behavioural changes were more dependent upon ontogeny of the retina. Auditory stimuli were not implicated for either menhaden or anchovy in responding to the stimulus used.

The present study examines the feeding habits of Alepocephalus rostratus, the only species of the family Alepocephalidae in the Mediterranean Sea and the second most important fish species, in terms of biomass, inhabiting the deep slope of the Catalan Sea. Samples were obtained at depths between 1000–2250 m. Diet was analysed for two different size-classes (immature and mature specimens) at three different bathymetric strata during two different seasons. The feeding habits of A. rostratus included a narrow range of mobile macroplanktonic organisms (e.g. Pyrosoma atlanticum and Chelophyes appendiculata) and some material of benthic origin. Pyrosoma atlanticum was the preferred prey item in spring at 1000–1425 m, being very scarce in summer at the same depth as a consequence of its scarcity in the environment during this season. There were some ontogenic differences in the diet of A. rostratus at 1425–2250 m. Adults ingested more and larger prey than juvenile specimens. The scarcity of resources below 1200–1400 m fostered a more diversified diet, as well as passive predation of sedimented material.