Evidence is provided that warming of the North Atlantic is responsible for the northward extensions of the ranges of warm water fish species, causing increasing numbers of southern immigrant species to appear off the Cornish coast of the UK. The increasing number of immigrant species is significantly correlated with temperature increases in the North Atlantic over the last 40 years.

An inventory of fish and epibenthic macrocrustaceans of the surf zones of sandy beaches along the Belgian coast was constructed. The surf zones were sampled intensively with a 2-m beam trawl in April–May 1996 (12 stations) and 26 species were recorded belonging to caridean shrimps (4), brachyuran crabs (5), cephalopods (1) and fish (16). The brown shrimp Crangon crangon dominated almost all samples (>80%). Total densities exceeded several times 250 ind 100 m−2 and 10 ind 100 m−2 if C. crangon was excluded. An east–west distinction as found in other (epi)benthic studies in deeper waters of the Belgian coast, was not found in the surf zone during this study. Spatial variation was mainly correlated with local characteristics such as turbidity of the water and the morphodynamic features of both the beach and the adjacent subtidal area.

Patterns of in situ fertilization success with respect to high and low tide periods are reported for the intertidal red seaweed Gracilaria gracilis which inhabits rock pools. Cystocarp (zygote) production was experimentally compared at high tide and low tide in both high- and low-shore tide pools at two sites using ten virgin female plants. High- and low-shore pools showed different patterns with respect to tide period. High-shore pools showed significantly greater numbers of cystocarps at low tide than at high tide whereas cystocarp production did not differ between high and low tide periods in low shore pools. The possible mechanisms of gamete release are discussed in light of these results.

A Dipolydora species (Polychaeta: Spionidae) was found in mud tubes attached to the larger tubes of the chaetopterid polychaete Chaetopterus cautus in Peter the Great Bay of the Sea of Japan. The worms were close in morphology to D. carunculata, a borer of various calcareous substrata and sponges described earlier from the same area. The chaetopterid-associated tube-building individuals usually differed from shell-boring individuals by the presence of black pigmentation on palps. However, some of them were not pigmented and appeared almost identical to D. carunculata. Isozymes of the tube-building and shell-boring individuals were compared using starch gel electrophoresis. Two of 16 studied isozyme loci proved diagnostic and unequivocally demonstrated the presence of two distinct species. The chaetopterid-associated individuals are described here as a new species, D. melanopalpa. Unbiased Nei's genetic distance between D. melanopalpa and D. carunculata (D=0·949) as well as the level of intraspecific genetic variation in either of them (D. melanopalpa, He=0·206±0·054; D. carunculata, He=0·239±0·044) are high and comparable to those of other electrophoretically studied polydorids. In contrast to other examined polydorids, D. carunculata and D. melanopalpa have the same numbers of expressed isozyme loci.

A description of the midgut gland of Gammarus locusta with the aim of using this organ as a complementary tool in ecotoxicological studies was made. The hepatopancreas is composed of two pairs of blind-ending tubular structures. The thickness and length of these tubules were ∼50 μm and 5 mm, respectively, in adult males (10–12 mm length). The distal part of each tubule is characterized by non-vacuolated E-cells typically exhibiting a relatively high nuclear to cytoplasmatic ratio. The epithelium of the remaining tubules is characterized by abundant columnar R- and F-cells, both ∼40 μm long. Large vacuolated B-cells (∼60 μm length) were very common along the midgut gland but seemed to increase in number in the proximal region of each tubule. An SEM examination revealed a delicate network of muscle fibres that limits the organ.

Baited traps deployed at 7800 m in the Atacama Trench off northern Chile, captured over 400 specimens of Eurythenes gryllus. This is the greatest depth of occurrence reported for the species. Of the 398 specimens available for study, all but three were female, giving a sex ratio very different from any reported previously. Female specimens measured 29–76 mm in length, and all were immature. Length/frequency distributions based on total length, peraeonite 1 length, and coxa 4 oostegite length were unimodal. Relationships between total length, and peraeonite 1 length, oostegite length, and wet weight were established. Oostegite development appeared to be precocious compared with published data. Subtle differences in peraeon, urosome, gnathopods, coxa 4, peraeopod 7, and epimeron 3 morphology, and the growth of oostegites separate Atacama Trench specimens from previously described material. The morphology exhibited by these specimens lies outside the known variability of E. gryllus, and suggests that this pan-oceanic entity may be undergoing incipient speciation.

The stomachs of 427 giant red shrimps, Aristaeomorpha foliacea, caught in the Strait of Sicily (Mediterranean Sea) during four seasonal surveys contained 73 cephalopods, or 8·6% of prey. Cephalopods ranked third as prey following crustaceans (49·2% of prey) and bony fish (20·5% of prey). The following cephalopod taxa were identified: Heteroteuthis dispar, Sepietta oweniana, Brachioteuthis sp., Abraliopsis morisii, Onychoteuthis banksii, Ancistroteuthis lichtensteinii, Histioteuthis bonnellii, H. reversa, Taoniinae sp., Octopodidae sp.; the dominant species was Heteroteuthis dispar (13 specimens). All remains pertained to small and very small specimens, including early juveniles; rostral length of 13 beaks (=17·8% of cephalopods) measured <1 mm. Early juveniles were found in stomach contents only in summer and winter. Cephalopod size was found to be positively correlated to shrimp size. No seasonal nor predator sex-related differences were found in the quantities and frequencies of ingested cephalopods.

This study was aimed at understanding the diet and the digestive function of the deep-living Lophogastrida species Lophogaster typicus (Mysidacea: Lophogastrida). Scanning electron microscopy (SEM) investigations have revealed that the mandibles exhibit typical features of a carnivorous diet, i.e. large and sharp incisor process and small molar one with only few scales. The analysis of gut contents confirms morphological data as crustacean remains have been recognized. However, the presence of a large quantity of unidentifiable soft particulate matter also indicates a saprophagous tendency. The external asymmetrical edge of the labrum consists of a small grinding area. The entire external face of the labrum exhibits numerous pores, which are related with glandular units. These units are organized into acini of two to four large cells. Two types of acini have been observed, i.e. with dark or clear cells. According to ultrastructural and cytochemical data, labral secretions are believed to be mucopolysaccharidic (for clear acini) and enzymatic components (for dark acini), and are therefore involved both in coating and in digesting the food. Moreover, presence of neuronal endings and endocrine cells, both associated with glandular units, and comparison between glandular units in starved and fed animals suggest a controlled release of the secretions. Therefore, the labrum plays a crucial role in the digestive function of the lophogastrid crustacean L. typicus, as it involves both mechanical and chemical breakdown of the food.

The population dynamics of the shore crab Pachygrapsus marmoratus was studied at two different rocky shores, Cabo Raso and Avencas, within the central Portuguese coast. The population structure at these shores, obtained by pooling monthly samples, revealed marked discrepancies. Unimodal, right-skewed size–frequency distributions at Avencas contrasts with the bimodal distributions obtained at Cabo Raso, corresponding to early recruits and larger adults. Recruitment timing and intensity together with habitat complexity are probable causes of the differences observed. At Cabo Raso an intense recruitment season was recorded from September to November, but very small juveniles were always present in samples. Monthly polymodal distributions are apparent but the size structure too complex to identify age groups through the sampling period. At Avencas, the influx of new juveniles is temporally restricted and year groups recognizable from main recruitment events taking place around October. Young-of-the-year crabs grow quickly to mature size and join the reproductive stock in the next breeding season from late March to early September in the study region. The growth pattern in both sexes follows a seasonal trend with minimum growth during the breeding months and maximum growth rates from late winter to early spring. Life span may reach four years, probably more in males. At Avencas, population maintenance seems to be highly dependent on favourable conditions promoting adequate settlement intensity and timing. Early recruitment is presumed to enhance the reproductive output of young-of-the-year individuals which comprise the bulk of breeding crabs. At Cabo Raso settlement rates are much higher and recruitment timing may be less critical since most breeding crabs belong to the 1-y+ class.

The habitat and feeding preference of two gastropod mesoherbivore species, Ansates (Helcion) pellucida and Lacuna vincta, inhabiting the kelp Laminaria hyperborea were investigated by studying the distribution, habitat choice and food preference of the herbivores between new and old kelp fronds. Nitrogen content and chemical defence (phlorotannin) level of the kelp fronds were measured in order to determine whether they were correlated with the feeding preference of the herbivores. The habitat choice of Lacuna vincta was correlated with the food preference of this species, while the habitat choice of A. pellucida probably was due to some other factor, e.g. competition or mortality. Ansates pellucida preferred to reside on the old fronds of Laminaria hyperborea, but consumed an equal amount of both tissue types. Lacuna vincta, however, preferred the new Laminaria hyperborea fronds both as habitat and food. There was a large variation in the phlorotannin content among the tissue samples of L. hyperborea. However, there were no overall statistically significant differences in tissue nitrogen or phlorotannin content between the new and the old L. hyperborea fronds.

Adult Nassarius reticulatus were exposed for two to three months to dissolved tributyltin (TBT), dibutyltin (DBT), triphenyltin (TPT) and diphenyltin (DPT) chlorides and to copper sulphate (CuSO4) in order to study the effectiveness of these compounds to induce imposex (penis and vas deferens development). The dialkyltins and copper did not promote imposex under exposure to 500 ng Sn l−1 and 500 ng Cu l−1. However, dissolved nominal concentrations varying between 100 and 500 ng Sn l−1 of TBT or TPT induced imposex in, respectively, 22 to 43% and 24 to 44% of the females. The testosterone titres of females increased significantly after two months' exposure to 250 ng Sn l−1 of TPT and TBT and the same happened to males exposed to 100 and 250 ng TPT-Sn l−1 and to 250 ng TBT-Sn l−1.

Settlement of Concholepas concholepas (Gastropoda: Muricidae) on natural and artificial substrata was studied between April 1999 and March 2001 at two sites in central Chile; the Las Cruces Marine Reserve and El Quisco Management and Exploited Area. Four different artificial materials were tested in the low intertidal zone during 1999 settlement season to determine their properties as settlement and microhabitat substrata for competent Concholepas larvae. Globular pads made of plastic filaments were identified as the best artificial collectors, exhibiting overall higher settlement rates than rock plots and lower variability among replicates within a given site. Thus, subsequent monitoring of settlement used only these globular pads that were replaced twice monthly. The temporal pattern of settlement was remarkably similar from year to year, starting at the end of austral winter (August–September) and ending in summer (December–January), defining a temporally restricted settlement season. Settlement at two sites within the Marine Reserve of Las Cruces was significantly higher than at sites in El Quisco. However, during the second settlement season, an additional site at El Quisco exhibited settlement rates comparable to those observed at Las Cruces. The results show that Concholepas settlement varies significantly over scales of several hundreds of metres as well as tens of kilometres, probably due to differences in coastal oceanographic conditions.

Death assemblages found in the Augusta Roadstead harbour (Mediterranean Sea) reflected some modifications in benthic environment that occurred since the 1960s, when the construction of dams closed the commercial harbour. In particular, evidence of a drop in the hydrodynamic levels were found, together with a mud sedimentation increasing. Furthermore, a turbidity phase characterized by a dominant Corbula gibba was identified as due to extensive dredging. Such temporary communities, distributed in accordance to the degree of instability and pollution, preceded the present day, very poor and destructured benthic assemblages.

Loligo gahi and Loligo sanpaulensis (Mollusca: Cephalopoda), two squid species presently under exploitation in the south-west Atlantic, are sympatric in coastal waters of northern Patagonia. In the present study, the morphometry of both species' northern Patagonian populations was analysed and compared. Relationships between the morphometric variables and mantle length, the standard measure of size for squids, are allometric in most cases. Weight and fin length show different rates of growth relative to mantle length in males and females of both species. Fin length, fin width and mantle length are the best morphometric variables to discriminate the mantle/fin complexes. Free rachis length, gladius length and gladius width are the most useful to separate both species' pens. The best discrimination of the tentacles is provided by the diameter of the central and marginal suckers and the number of teeth on the three largest sucker rings. Discriminant functions are provided to allow the classification of individuals from both species and the identification of pens and tentacle clubs found in predators digestive contents.

A series of measurements were taken from 50 random examples of the arborescent sponges Raspailia ramosa and Stelligera stuposa at a number of sites and depths at Lough Hyne, Co. Cork, Ireland. Sites ranged from fast flowing habitats, experiencing little sediment settlement, to the converse where current flow was extremely slight and sediment settlement rates high. Depth intervals at which sponges were measured ranged from 6 to 24 m. Sponges of both species varied with respect to measurements taken and the growth proportions (ratios of measurements taken). The greatest morphological differences occurred between depth and current extremes. However, at the most sedimented site (24 m) branching complexity of both species actually decreased in opposition to the proposed current models. It is discussed that simple morphologies (such as singly dichotomized sponges) may be better suited to extremely sedimented regimes being more erect than larger, more complex specimens. Other biological factors that may limit branching complexity are considered and emphasis is placed upon the possible inadequacies of community or group level models of morphological adaptation.

Sea urchins were collected in August 1999, at Salvador (Todos os Santos Bay, State of Bahia, Brazil). Twenty out of 20 Eucidaris tribuloides sea urchins studied had sponge remains in their guts, 12 of which, in large enough quantities to discard the hypothesis of sponge contamination on other food items. No other macroscopic evidence of alternative food sources has been encountered. Sponges found in large enough quantities were classified in seven genera, spread over seven families and five orders of the Demospongiae. Among the commonest sponges were Haliclona spp. and Iotrochota birotulata. The results show clearly the spongivorous habit of E. tribuloides at the studied site.

The rates of ingestion, egestion, ammonium excretion, and CO2 respiration of Tripneustes gratilla (Echinodermata: Echinoidea) from a shallow water embayment at eastern Mactan Island, central Philippines were examined. There was no significant difference in weight-specific feeding rate with the three macrophytes (Sargassum polycystum, Thalassia hemprichii, and Kappaphycus alvarezii). The power function equation, M=KWb fitted well with the weight-specific egestion rates ((r2=0·93), weight-specific CO2 respiration rates (r2=0·92) and ammonium excretion rates (r2=0·86). Weight-specific egestion rates, CO2 respiration and ammonium excretion were indirectly proportional to body weight. For weight-specific egestion rate (in μg DW faeces/g DW urchin-h), the regression coefficient, b and constant, K were −2·31±0·68 (mean±SE) (P=0·02) and 6359·55±5394·31 (P=0·29), respectively. The b and K for CO2 respiration were −1·28±0·48 (P=0·04) and 39·72±10·59 (P=0·01), respectively. For ammonium excretion, the b and K were −1·03±0·46 (P=0·11) and 262·51±56·89 (P=0·02), respectively.

Elemental composition and ontogenic change patterns of Sr and Ca were examined in conger eel, Conger myriaster, otoliths. Accumulations of the major elements of seawater, K, Mg, and Na, into otoliths were smaller than the accumulations of 19 other minor elements whose concentrations were determined. Strontium content and Sr:Ca ratios in the otolith fluctuated during the life history transect at 100 to 200 μm from the core of the otolith, indicating a period of metamorphosis. Changes in Sr content and Sr:Ca ratios may be associated with internal physiological factors such as metamorphosis in the early developmental stage in the conger eel.

0-group bass were sampled from the shallow creeks of the Tamar and Camel estuaries at regular intervals from May to September in 1981 to 2000 to measure relative year-class abundance. From 1989 onwards classes were generally strong, especially those of 1989, 1992 (Tamar only), 1995 and 1998. Sampling at age-4, before departure from the nursery at the onset of adolescent movements, gave broadly similar relativities. Numbers were greater, and growth faster, in the Tamar than in the smaller and cooler Camel. Temperature was an important factor in both abundance and growth. Occasional major differences in abundance between the two estuaries were reported. Factors which might bias the age-4 result are considered. Other estuaries on the south side of the south-west peninsula, sampled less frequently, reflected Tamar abundances; others on the north side reflected Camel abundances. Limited analysis of stomach contents of older juvenile bass often present in the same habitats revealed no evidence of cannibalism on 0-groups. The shallow creeks of the Tamar and Camel were deserted in winter but a deeper creek on the Taw, frequented throughout winter, was sampled monthly in the 1982–1996 winters to measure losses, if any, in cold periods. In the mainly mild winters, losses were infrequent and small except in the five-week cold spell of early 1986, when the 1985 class suffered an estimated 58% loss in the Taw and possible total loss in the Camel and the Tamar. Sudden heavy flooding of the estuaries caused no apparent losses when they occurred in late summer and autumn but might be damaging if they occur soon after post-larvae arrive.

Analyses of 13 submersible dives on the continental slope of the Bay of Biscay (north-east Atlantic) showed that: (i) orange roughy formed dense aggregation of more than 4000 individuals per ha close to the bottom of a small underwater canyon. In all other study areas only a few individuals were observed. Orange roughy aggregations are probably associated with areas of high water mass movements and mixing; (ii) most individuals observed within this aggregation or in its peripheral areas were behaviourally inactive and could be approached with the submersible at close distance; (iii) a large number of these orange roughy showed a completely pigmentless white, or weak red coloration, never observed from specimens caught in trawls. Two individuals which were disturbed by the submarine changed from white to the ‘typical’ red coloration.

These observations suggest fine tuning of the foraging strategy and life cycle of the species. It is speculated that, as an active predator of a sparse food resource, orange roughy has developed adaptations to exploit areas with specific hydrological conditions which offer high prey encounter rates and shelter during metabolic relaxation phases between foraging trips.