Multiple locus allozyme heterozygosity has been shown to be weakly, but significantly correlated with certain fitness parameters in bivalves. Immune function of individual Mytilus edulis from the Menai Strait, Wales, UK was assessed monthly over one year (1997–1998) by measuring total blood cell (haemocyte) counts, differential haemocyte counts (% basophils and eosinophils), phagocytic capability (by zymozan uptake) and intracellular superoxide generation. Sampled mussels were also scored at 9 allozyme loci. Mussels were then grouped into multiple locus heterozygosity (MLH) classes and plotted separately against the different measures of immunocompetence. No significant association was present between MLH and total haemocyte count, phagocytic capability or intracellular superoxide generation. However, there was a significant association between MLH and the character (basophilic or eosinophilic) of circulating haemocytes (r2=0·057, P=0·002). Highly heterozygous individuals tended to have significantly more eosinophilic haemocytes circulating in the blood than highly homozygous individuals. Eosinophilic haemocytes are known to have a high capacity for phagocytosis of invading organisms and these results may therefore be interpreted as increased health (=fitness) in more highly heterozygous individuals.

Measurements on cultivated larvae and data from the literature demonstrate that length and width of pelagic sea lice larvae, Lepeophtheirus salmonis and Caligus elongatus, are overlapping. Therefore measurements on planktonic developmental stages are of little practical value in specific identification. A standard WP-2 net with 200-μm mesh size will, in practice, collect free living sea lice larvae satisfactorily. The naupliar and copepodid stages of sea lice are illustrated and pigment distribution described. Larvae of L. salmonis are characterized by black and brown pigment, those of C. elongatus by red. The distributions of pigment are distinctive in the species mentioned, and in pelagic larvae of Lepeophtheirus pollachius and L. pectoralis which also are measured, described and illustrated for comparison. The copepodid stages of larvae are different in shape of pro- and urosome, morphology and armature of the maxilliped, distribution of pigment and its colour. The black and brown pigmented copepodid of L. salmonis is slender and oval in outline, somewhat pointed anteriorly, broadest in the middle of prosome and more narrow posteriorly. The proximal segment of the maxilliped is robust without seta, but the subchela has a slender branching barb with three to five ‘fingers’. The red pigmented prosome of C. elongatus is elongate, broad anteriorly with two lateral notches. The extreme breadth of the copepodid is clearly before the middle of the prosome. The corpus of the maxilliped is elongate and equipped with a seta. In addition the appendage has a medial 2-divided process.

The pattern of planktonic abundance of juvenile Hydrobia ulvae was investigated in the Ria de Aveiro, Portugal, with the use of floating artificial collectors made of ‘hoghair’ filter, which were deployed for 2-day consecutive periods during 3·5 months. Abundance in the collectors followed a remarkably regular semilunar pattern, being higher during spring tides around full and new moons. Cross-correlation analysis between tidal range and captures in the collectors indicated a period of oscillation of the captures of 15 d, with maximum captures tending to occur on the day of the highest amplitude tides. The physical and behavioural mechanisms responsible for the pattern remain largely unknown. However, results from a simple model assuming that migration from the sediment to the water is dependent on current velocity suggest there is a minimum threshold in average current velocity integrated along the tidal cycle (and, therefore, in tidal amplitude) above which juvenile H. ulvae exhibit the floating behaviour. Artificial collectors may provide an effective and relatively easy and inexpensive technique for the study of dispersal of post-metamorphic molluscs.

The integration of molecular and morphological approaches has produced substantial progress in understanding the higher classification of most major invertebrate groups. The striking exception to this is the Polychaeta. Neither the membership nor the higher classification of this group has been robustly established. Major inconsistencies exist between the only comprehensive cladistic analysis of Polychaeta using morphological data and the DNA sequence studies covering all or part of the taxon.

We have compiled a dataset of available nearly complete 18S ribosomal DNA sequences and collected an additional 22 sequences (20 Polychaeta in 19 taxa, one Myzostomida and one Phoronida) to obtain more comprehensive coverage of polychaete diversity for this gene. Analyses of the data do not resolve all inconsistencies among current hypotheses of polychaete phylogeny. They do support the recognition (in whole or part) of some clades such as the Eunicida, Phyllodocida and Terebellida that have been proposed on morphological grounds. Our analyses contradict the Canalipalpata and the Scolecida. Although the polychaete sister-group to the Clitellata is not clearly resolved in our analyses, the clitellates are always recovered as a derived clade within the Polychaeta. Increased taxon sampling is required to elucidate further the phylogeny of the Polychaeta.

Interannual and spatial differences in the abundance of Metridia lucens are reported from the Irish Sea from 1996 to 2001. In most years the abundance in spring is very low (<50 m2), however in 2001 the abundance was high and this enabled a rare study of the vertical distribution of M. lucens in coastal waters. The vertical distribution differs with time of day and water column structure. Abundances were always higher in stratified deeper waters compared with mixed or coastal waters.

The effect of light intensity on the course of embryonic development of squid (Heterololigo bleekeri) was examined. Heterololigo bleekeri embryos at an early stage were incubated in the egg cases under six to seven gradients of light intensities which varied from constant darkness to intensive light >1000 lx (12L:12D for all experimental groups except for the constant darkness group). Duration of hatching in every experimental group ranged from seven to 15 days with a peak for ≈30–50% of total number of hatchlings. However, there were no particular relationships between light intensities and duration of embryonic development, duration of hatching, number of hatchlings at hatching peak, and body size of hatchlings. In all groups, body size of hatchlings increased up to seven days post-hatching and thereafter did not change remarkably. Just after hatching, strongly positive photo taxis was observed for H. bleekeri

The diet and functional biology of the digestive system of the cephalaspidean gastropod Haminoea orbygniana was investigated by gut content analysis of animals collected in the Ria Formosa, a coastal lagoon in southern Portugal. The results show that this species is herbivorous, stenophagic and probably non-selective, feeding mainly on diatoms (67·61%) and occasionally on vegetal detritus (4·16%) and Foraminifera (0·04%), but also including sand grains as an important part of the gut contents (28·34%). The role of the gizzard plates in the fragmentation of diatom frustules was demonstrated and is discussed. Data reveal that this process, although possibly important for the digestion and assimilation of food, seems not to be crucial. The role of sand as an additional food source and as an accessory tool complementary to the gizzard plates is discussed. A general review of the diet within the family Haminoeidae is presented, with all recent work indicating that they feed on diatoms and green algae.

Sex ratio and size–gender distribution of Coralliophila meyendorffii and Babelomurex cariniferus collected in the field was studied. While sex ratio did not depart from the expected Fisher 1:1 ratio for dioecious species, the size–frequency distributions showed clearly a sexual size dimorphism with males significantly smaller than females. Laboratory monitoring of penis reduction in both species, combined with an anatomical and histological study of the reproductive system of individuals reducing penis revealed the existence of transitional sexual stages, proving the existence of protandry. Penis monitoring also demonstrated a high plasticity in size at sex change, suggesting a socially controlled sex change. In C. meyendorffii, where penis monitoring followed an experimental design based on the assumption that protandry existed and that presence of females influenced sex change, results strongly supported a social control of sex change. Evidences for protandry in other coralliophilids are summarized and protandry as a widespread sexual strategy in Coralliophilidae is postulated.

A new pedunculate barnacle, Ashinkailepas seepiophila gen. and sp. nov. has been recovered from a hydrothermal cold seep at 1175 metres of depth off Hatsushima Island, Sagami Bay, central Japan. It is the second record of a Neolepadinae, otherwise known from vents, from a seep, but the two are not closely related. Its coarsely ornamented capitular plates, and primary peduncular armament being in whorls of six plates, distinguish it from all previously known neolepadines, not only as a new genus and species, but also as a distinct clade, and therefore a new tribe is proposed to accommodate it. There is a slight bilateral asymmetry in the proportions of the capitular plates as well as a marked bilateral asymmetry in the arrangement of the peduncular scales related to bending over to one side. This apomorphic characteristic distinguishes the new species from all other Scalpellomorpha. While leaning over to one side is suggestive of verrucomorphs, it is not judged a sign of affinity. Ashinkailepas is apparently the most primitive of the vent/seep barnacles, which are considered relics largely of the Mesozoic age.

A phylogenetic analysis of the polychaete clade Terebelliformia (Terebellida) was undertaken in order to test monophyly of families and subfamilies and to determine their affinities. Parsimony analyses of 41 terebelliform species with outgroup Owenia fusiformis and 46 morphological characters yielded 106–144 most parsimonious trees with length 250, consistency index=0·432, retention index=0·659 and rescaled consistency index=0·285. Monophyly was indicated for Alvinellidae, Ampharetidae, Terebellidae and Trichobranchidae and the terebellid subfamily Polycirrinae. Monophyly of Terebellidae is supported by the presence of a ridge-like tentacular membrane. Monophyly of Polycirrinae is supported by the loss of branchiae, trilobed upper lip, pinnate secondary notochaetae and ventro-lateral pads. Recognition of Polycirrinae renders taxa in the other terebellid subfamilies—Terebellinae and Thelepodinae—paraphyletic. Our results do not support previous classifications that placed Trichobranchidae as a subfamily of Terebellidae; rather it should be considered equal in rank with Alvinellidae, Ampharetidae, Terebellidae and Pectinariidae. The following relationships were obtained: (Trichobranchidae ((Alvinellidae, Ampharetidae) (Pectinariidae, Terebellidae))). This is the first time a Pectinariidae–Terebellidae sister group relationship has been found; it is supported by the synapomorphic presence of ventral glandular shields.

To assess the phylogenetic interrelationships of Trichobranchinae (Polychaeta: Terebellidae), we present the results of a cladistic analysis based on morphological characters coded as contingent. We also present an alternate way to number anterior segments, based on a reinterpretation of prostomial and peristomial morphologies in different genera. The ingroup terminals included 28 species, and the outgroup included one species of Ampharetidae and four species belonging to other subfamilies of Terebellidae. The monophyly of Trichobranchinae is clearly supported by the presence of long shafted uncini in thoracic neuropodia and by the absence of ventral shields. Species of Terebellides share lamellate branchiae, uncini with a long and narrow manubrium without denticles and uncini with a long and sharp main fang in the eighth segment. Species of Octobranchus share subquadrate branchiae on segments 3, 4 and 5, notopodia first present from segment 4, and uncini with a long shafted manubrium first present from segment 6. The autapormophy for Unobranchus is the presence of a single filiform branchia on segment 3. Artacamella falls into one of the Trichobranchus clades and is treated as a junior synonym of the latter.

This is the first record of the epizoic barnacle (Octolasmis angulata) on the crab Charybdis feriatus. Prevalence of O. angulata was 85·7% and mean intensity of infestation was 59±64·5 (range 3–239). Prevalence and mean intensity of infestation increased with host size in the range 55–120 mm carapace width. Barnacles occurred most frequently on the gills, anterior branchial chamber wall in the epibranchial space, occasionally on the wall of the branchial chambers beneath the gills and on the scaphognathite within the branchial chambers. Most barnacles were observed on the hypobranchial surface of the gills.

DNA was extracted from mucus secreted by snails that had been allowed to crawl over glass microscope slides. The mucus contained many epithelial cells and a few blood cells. Microsatellite DNA regions were amplified using template DNA from the mucus and clear bands obtained showing the same positions as when using template DNA from the foot. Pedal mucus is therefore a reliable source of DNA, which can be extracted by a simple methodology that is readily applied in the field. The technique has considerable potential for conservation- and behavioural ecology.

Reproductive aspects of Eledone moschata from the Spanish waters of the Gulf of Cádiz are reported for the first time. The species is relatively abundant over the continental shelf and it is caught as by-catch by the bottom-trawl fleet. Monthly samplings throughout one annual life-cycle showed a sex ratio with a female dominance (0·45:1). A four stage maturity scale was used for both sexes. The reproductive period was determined from monthly evolution of these stages as well as that of several maturity and condition indices. The breeding season extended from October to June, with spawning peaks in October and March–May, the second one being more important. Length and weight at maturity (mantle length50, body weight50) were estimated at 7·8 cm and 97 g in males, and at 12·2 cm and 274 g in females, respectively. Total fecundity, estimated from 52 mature females, was 443·5±154·4 oocytes on average. The mean size of mature oocytes and the mean length of mature spermatophore in mature females and males was 10·24 mm (±1·07) and 13·88 mm (±1·60), respectively.

A pedunculate barnacle, Leucolepas longa, occurs in densities over 1000 individuals m−2 on the summit of a small seamount near New Ireland, Papua New Guinea. Most of the population grows on vesicomyid clams projecting from sulphide-rich sediments, or on their dead shells, but the barnacle also settles on rock and on tubes of a vestimentiferan. Collections of several hundred barnacles allowed comparison of population and reproductive characteristics. The barnacle is a suspension feeder with a lightly-armoured stalk that can grow to 40 cm above the bottom. Growth appears to be rapid and both reproduction and recruitment are continuous. The barnacles brood egg masses within the capitular chamber and 46% of one sample was brooding. Lecithotrophic nauplii released upon retrieval to the surface were cultivated for 45 days. Metamorphosis to Stage IV yielded an actively swimming larva about 1 mm long overall, which still contained lipid reserves, indicating capacity for wide dispersal.

Population differences were measured in the tolerance of Littorina saxatilis from sites around the Isle of Man, to acute exposure to zinc, lead, copper and cadmium. Animals from a site influenced by disused mine run-off in Laxey estuary (high zinc) were compared with animals from less contaminated estuaries (Peel-high lead, but lower zinc), and the relatively uncontaminated Castletown and Ramsey estuaries, plus the open coast near Derbyhaven. Median lethal times (LT50) were estimated for each test concentration (5, 10, 20 mg l−1 Zn; 5, 10 mg l−1 Pb; 0·5, 1·0, 2·0 mg l−1 Cu and Cd) except for those that did not produce sufficient mortalities. Individuals from Laxey estuary showed significantly higher tolerances to zinc (10 mg l−1) and lead (5 mg l−1) than animals from the unpolluted sites. No co-tolerance to copper or cadmium was apparent. Population tolerance to zinc was correlated with reduced accumulation rates. Lead tolerance may result from the ability of the tolerant individuals to sequester the metal and detoxify it in their tissues; the littorinids from Laxey had significantly higher rates of lead accumulation.

Argopecten purpuratus was exposed to two different diets which reflected short term variations in quantity and quality of the natural food supply typical in bays of southern Chile. No significant differences of clearance rate were observed over different time periods at either of two food concentrations. The scallop reduced its clearance rate significantly when it was exposed to the higher food concentration. Pseudofaeces production occurred only at this high diet and the time factor had no significant effect on this process. The organic content of pseudofaeces was significantly lower than the organic content of the food, suggesting a pre-ingestive selection mechanism. Based on this capacity for particle selection, A. purpuratus was able to compensate for the differences in food quality of the experimental diets and ingesting particulate material containing 38% organic matter as a result of the selection process when fed at the higher food concentration. Absorption efficiency was lower following exposure to the high food concentration, suggesting that the experimental time of 72 h was not sufficient to acclimate the digestive response to a food supply significantly different from that of its habitat of origin. Phytoplankton form the principal nutritional source for this epibenthic species, and resuspended detritus, although occurring in large quantities, may only be of importance once digestive processes become acclimated to processing them.

The age of the sea urchin Hemicentrotus pulcherrimus in Oshoro Bay at the northern distributional limit of the species was ascertained by counting black bands in charred genital plates after etching. Consequently, the seasonal growth of two year-classes was monitored and the seasonal changes were related to the reproductive cycle and water temperature. A black band at the edge of the genital plates was found in more than 50% of the sea urchins from September to November. No statistical difference of the test diameter and body weight forming the bands between the estimated and actual values showed that the band is formed annually and can be used as a chronometer. The sea urchin grew rapidly for one and a half months, from late August to late September or early October when water temperature reached a maximum of >20°C, then began to fall while the gonads increased in size prior to maturation. Growth ceased during October to November with initiation of gonadal maturation and the peak of black band formation in genital plates. Spawning occurred from March to May, later than in southern Japan. The annual cycle of growth and reproduction of H. pulcherrimus may be flexibly adapted to surbarctic waters.

A new barnacle, Chthamalus neglectus sp. nov. is described from Hong Kong. Light microscopy and scanning electron microscopy investigations of adult morphology show obvious differences from previously recorded Chthamalus species, and that this species belongs to the ‘C. challengeri group’ of Chthamalidae.

The intraspecific variation in the number and distribution of paragnaths in ten populations of Nereis (Neanthes) virens collected throughout its range was examined. Significant differences among populations are found in the total number of paragnaths and in each paragnath group. The unweighted pair-group method using arithmetic averages cluster analysis revealed three distinct clusters separating Canadian populations, Europe/USA populations and the Japanese population, suggesting the implication of either restricted gene flow, selection on paragnath patterns or phenotypic plasticity. Comparison with a previous genetic study suggests that morphological variants represent ecotypes of the single, widely distributed N. virens species.