Females of the new species Exrima walteri sp. nov. were found in sediment trap samples deployed over different sites of the East Pacific Rise (13°N) at 2600 m depth. Four traps were deposited during the HOPE99 cruise (1999) and recovered during the AMISTAD (1999) cruise on the research vessel ‘L'Atalante’. The new species is distinguished from congeners, E. singula Humes, 1987 and E. dolichopus Humes, 1987, by the following derived characters: first somite of the urosome with 3 (one dorsal and two lateral) stout conical extensions; distal endopodal segment on the swimming leg 4 broad. In addition, many specimens of copepodids I and lecithotrophic nauplii, identified as belonging to Dirivultidae gen. sp., were found in the samples of all sediment traps. This is the first record of copepodids I and of a nauplius of dirivultids from the Pacific Ocean. Study of type and additional material collected during different Ifremer cruises at different vent sites (HERO91, EXOMAR, PHARE and MoMARETO) required synonymy of four species of Aphotopontius Humes, 1987, Stygiopontius Humes, 1987 and Rhogobius Humes, 1987. Aphotopontius rapunculus Humes and Segonzac, 1998 is transferred to the genus Rhogobius because it possesses all presumed derived attributes of this genus: last abdominal somite with lobes at sides of anal operculum; second segment of antennal endopod elongate and slender. A new study of the type material suggests that: Aphotopontius temperatus Humes, 1997 is a synonym of A. atlanteus Humes, 1996; Stygiopontius lumiger Humes, 1989 is a synonym of S. sentifer Humes, 1987 while S. bulbisetiger Humes, 1996 is a synonym of S. pectinatus Humes, 1987. Females of the three synonymized species were found to be sub-adult females at copepodid V. Leg 6 on these specimens is one seta located dorsolaterally on the posterior part of the genital somite. This position for leg 6 is unknown for copepodid V of other siphonostomatoids whose leg 6 is located ventrally at copepodid V; the dorsolateral position is presumed derived and shared by the dirivultid genera Aphotopontius Humes, 1987 and Stygiopontius Humes, 1987. A new key to the Dirivultidae genera is presented.

Variation in life history characteristics is believed to play an important role in dispersal and thus shaping the population and genetic structure of marine invertebrates. The genetic structure of Ibla cumingi, a small intertidal stalked barnacle that broods lecithotrophic larvae, was evaluated using 145 random amplified polymorphic DNA markers on 100 individuals from five locations across Hong Kong waters. Shallow genetic structure was observed along open-coast shores, and there was no indication of isolation by geographical distance. A significant genetic divergence, however, was observed between samples inside and outside Tolo Harbour, a semi-enclosed, sheltered and estuarine bay located in the north-eastern quadrant of Hong Kong, indicating the presence of a genetic sub-structuring pattern. In addition, relatively lower genetic diversities were described for samples inside Tolo Harbour than those from open-coast shores. This could be associated with an increase in inbreeding events attributed to local settlement caused by larval retention. This study provides an insight into how the interaction of life history and local, enclosed, hydrographic conditions could result in a substantial genetic structuring of I. cumingi over a meso-scale geographical distance.

The preference for two shell species, Monodonta labio form confusa and Thais clavigera, was compared between two populations of the hermit crab Pagurus filholi from Oura Bay, Shimoda, central Japan and from Hakodate Bay, Hakodate, northern Japan. Hermit crabs from Oura Bay preferred T. clavigera to M. labio form confusa, whereas crabs from Hakodate Bay preferred M. labio form confusa. The shell of T. clavigera was more effective against desiccation and high temperature stress but heavier than M. labio form confusa. The preference of P. filholi from Oura Bay for T. clavigera may be attributable to the greater requirement for protection against higher physical stresses, even though a higher energetic cost related to the shell weight is incurred.

Morphological variations of Tunisian Lithognathus mormyrus populations were investigated using 41 morphometric measurements (27 truss elements and 14 traditional measurements) and eight meristic characters collected from ten marine and lagoon samples. Statistical analyses (e.g. discriminant function analysis (DFA)) performed separately to truss and traditional data revealed a significant degree of morphological dissimilarity of lagoon samples (Bizerta, Ghar El Melh and El Biban lagoons). For these three lagoon environments the overall assignment of individuals into their original sample (percentage classification success) by DFA was 94% for truss elements and 98% for traditional measurements. This morphological discrimination among lagoon samples, revealed with traditional measurements, seems to be associated only with the anterior part of the body (especially with the pre-orbit and snout length). However, for truss analyses, it was explained by both anterior and posterior parts (peduncle region). Statistical analyses for only marine samples showed partial overlapping with significant morphometric variation of the Chebba and Gabès samples mainly related to the anterior part of the body, for the first sample, but also to the posterior region, for the second one. These morphometric variations are often due to environmental conditions and mainly to the exploitation of different ecological niches that are particularly limited by the availability, type and size of prey. Thus, truss and traditional approaches are complementary and provide more accurate explanations of such a morphological discrimination. Meristic character analyses showed homogeneity of striped seabream samples, except for the Ghar El Melh lagoon sample which quietly differed from the others. This distinction was mainly explained by the number of soft anal rays.

Rhodoliths or maërl are calcareous nodules of coralline red algae growing unattached to the substrata. They sustain a high biodiversity, being one of the most important marine benthic environments dominated by macrophytes. Sabellariidae are tube-dwelling filter feeding marine polychaetes that build their tubes by secreting cement from their thoracic glands. Some species are solitary, while others build tubes together, forming large aggregates. This study analyses Sabellariidae collected in rhodolith beds along the subtidal zone of the coast of João Pessoa and Cabedelo, Paraíba, north-eastern Brazil. A total of 100 individuals of six species were identified. Four are reported for the first time for the north-east coast of Brazil: Phragmatopoma caudata Mörch (1863), Sabellaria bella Grube (1870), Sabellaria nanella Chamberlin (1919), and Sabellaria wilsoni Lana & Gruet (1989). The first occurrence of Sabellaria pectinata Fauvel (1923) along the western Atlantic is provided as well as the description of a new species of the genus Sabellaria.

Armina is the most species-rich genus of the Arminidae family with over 50 nominal species. Material of the genus Armina from the western Atlantic and the eastern Pacific was revised. Six species have been documented from the western Atlantic; however, we have determined that only four of them are valid: Armina muelleri, A. wattla, A. juliana and A. elongata. Also, only three out of seven species previously registered in the eastern Pacific were recognized in the present study: A. californica, A. cordellensis and Armina sp., an unnamed species. The phylogenetic analysis of 13 taxa and 17 characters was performed using the program PAUP (Phylogenetic Analysis Using Parsimony). The Branch-and-Bound algorithm generated a 29-step tree with the following relations: (Histiomena convolvula, (Dermatobranchus sp., ((((A. californica , (A. maculata, A. muelleri)), ((A. loveni, A. neapolitana), A. wattla)), (A. cordellensis, (Armina sp., A. juliana))), (A. tigrina, A. elongata)))). The monophyletic evidence for Armina is discussed and compared to possible speciation processes similar to those found in other Opisthobranchia groups.

Following the ‘Volgoneft-248’ oil spill, phytoplankton distribution within the affected area was investigated for two years. Simultaneously measured physical variables such as salinity, temperature, Secchi disc, current speed and direction, and total petroleum hydrocarbons (TPH) were evaluated together with phytoplankton data. At the time of the accident, the TPH concentration in surface water was measured as 2.17 mg l−1 and decreased to 88.5 µg l−1 after five days. In the first sampling period, no diatoms were detected in surface water, while dinoflagellates were dominant in the phytoplankton community. The species composition of phytoplankton changed rapidly in two months and the diatoms increased in terms of abundance and diversity. This indicated that the diatoms might be more sensitive to oil pollution than the dinoflagellates. In comparison with the historical datasets, the low phytoplankton abundance following the oil spill should be considered as the small effect of oil on the phytoplankton rather than natural variability of the ecosystem. High oil concentration in the water column caused stress on the phytoplankton and influenced the species composition negatively depending on the sensitivity of groups and the natural variability of the ecosystem.

The genus Opaliopsis from Brazil is revised based on three deep-water species. Opaliopsis atlantis (Clench & Turner, 1952) is confirmed as occurring in north-eastern and south-eastern localities. Opaliopsis opalina (Dall, 1927) is reported for the first time in the south-western Atlantic. A new species, Opaliopsis cearense, is described from the north-eastern Brazilian coast, and is distinguished by its large number of fine spiral cords per teleoconch whorl.

An endoparasitic platyhelminth from six species of sacoglossan opisthobranchs was collected at several localities of temperate to subtropical waters in Japan. Poecilostomatoid copepods (all species of Splanchnotrophidae and several species of Philoblennidae) and a few digenean flukes had been the only endoparasitic metazoans known for opisthobranch hosts. The newly discovered parasite was 1 to 15 mm in length and had no eyes, mouth, pharynx, or intestine. It had no external organs for parasitic life (e.g. attachment organs) and inhabited the haemocoel of the host. When mature, it emerged from the host and secreted a silky substance around itself to form a cocoon. The cocoon contained egg capsules with 19–42 eggs. Larvae, hatched from the capsule, had a ciliated body and a pair of eye spots. They were negatively phototactic and capable of invading suitable hosts. These morphological and life history features suggest this parasitic worm may belong to the family Fecampiidae (Platyhelminthes: Turbellaria), one of a few obligate parasite taxa in Turbellaria. Molluscan hosts which are common for parasitic Platyhelminthes have not previously been known for this family. The newly discovered parasite may be important for understanding the evolution of parasitism in Platyhelminthes.

An inventory of the main epibiont organisms on living specimens, on empty shells and on pagurized shells of Fusitriton magellanicus collected in Zygochlamys patagonica fishing grounds off Argentina is provided here. Additionally, considering that the presence of the thick, hairy periostracum could be an inhibitor of boring and encrusting species, we analyse the presence of a periostracum in living F. magellanicus in relation to the presence of epibionts. More than 70% of all shells bore encrusting organisms (of at least 30 taxa) but only a small proportion of shells was heavily fouled, the majority of living, empty and pagurized shells being lightly or moderately fouled. Polychaetes were the most common epibiont group (present on more than 60% of shells) while sponges and ascidians were responsible for the majority of the heavily fouled living gastropods. In general, specimens had a moderate level of encrustation and, simultaneously, a low or medium coating of periostracum. Hairy gastropods (only 14% of the sampled specimens) had few or no epibionts. A relationship between the size of the shell and the level of encrustation was only found in living gastropods. Fusitriton magellanicus is the second species in importance (after the Patagonian scallop) for the provision of a hard settlement substrate in the shelf-break frontal area of the Argentine Sea.

The study presents dry mass and body measurements of the larval stages of five common barnacle species occurring in mesozooplankton catches of Southampton Water and the central Solent area of the south coast of the UK. Quantitative samples were collected with conventional 120-μm mesh plankton nets. Species-specific regression equations relating carapace width and total length with dry mass were obtained for stage II to stage VI nauplii and cyprids of Austrominius modestus, Amphibalanus improvisus, Balanus crenatus, Semibalanus balanoides and Verruca stroemia. Width–dry mass and length–dry mass regressions obtained in the present study accounted for more than 98% of the variability for naupliar stages, and length–dry mass for 80% of the variability for cyprids. The dry mass of barnacle larvae predicted from carapace width equations determined here differed by only –6% from the measured dry masses of an independent data set, suggesting these first-reported equations of barnacle larvae are useful additions to zooplankton production studies.

A new species of Sphaerodoridae (Annelida: Polychaeta), Sphaerodoropsis solis sp. nov., is described from the Challenger Plateau in the Tasman Sea, south-west Pacific. It is the third species of the genus with ventral macrotubercles and is further characterized by the lack of dorsal papillae and the specific arrangement pattern of ventral papillae. A character indicating sexual dimorphism, that has been observed in three morphologically similar species, S. arctowskyensis Hartmann-Schröder & Rosenfeldt, 1988, S. bisphaeroserialis (Hartmann-Schröder, 1974c), and S. garciaalvarezi Moreira, Cacabelos & Troncoso, 2004, is confirmed for S. solis sp. nov. Besides S. solis sp. nov., S. arctowskyensis and S. parva (Ehlers, 1913) are newly recorded from the Challenger Plateau and the East Campbell Plateau in the south-west Pacific. An updated key for the genus Sphaerodoropsis is provided.

Intracapsular oxygen availability is one of the main factors affecting embryo development of marine gastropod species with encapsulation. This is because the low solubility and diffusion rate of O2 in water, plus the low oxygen diffusion rate that the capsule wall presents, reduces oxygen inside capsules. In addition, temperature affects embryo development inside capsules through its effect on embryo metabolic rate and oxygen availability. In spite of both factors being highly correlated and that a synergic effect on embryo development may be expected, there are few studies evaluating temperature and intracapsular oxygen availability simultaneously. In this work we evaluated the role of the capsule wall of the marine gastropod Chorus giganteus as a barrier for oxygen diffusion and its interaction with temperature affecting intracapsular oxygen availability and embryonic development. For that, we cultivated capsules in seawater at three different temperatures, 9, 12 and 15°C, for a time to complete embryo development. Oxygen level was measured inside capsules with and without embryos, and outside capsules at all temperatures. The number of capsules successfully hatched at the end of the experiment, and early and late embryo mortality were recorded. Finally, we measured embryo metabolic rate at the three different temperatures assayed. We found that embryo mortality and abnormal morphological development were more frequent at higher temperatures. Intracapsular oxygen availability decreases at higher temperatures in capsules with and without embryos. These results may be explained by an increase in the total intracapsular embryo metabolic rate (per capsule) with temperature and an inadequate oxygen diffusion rate from seawater through the capsule wall and intracapsular fluid to the embryonic cells. Our findings suggest that encapsulation is constrained at high temperatures in C. giganetus affecting significantly its reproductive success. This may have important consequences in a scenario of global warming.

The number of eggs produced by a parental stock is central to fisheries advice on recruitment potential. However, stock based estimates of egg production may give a misleading index of recruitment potential in stocks containing several reproductively isolated populations. This paper examines the ability of length, condition and oocyte developmental stage to predict levels of potential fecundity in the sandeel, Ammodytes marinus, in three important fished areas in the North Sea. Our results indicate that regional variation in this relationship exists, with fecundity in central areas of the North Sea being higher than those found just off the north-east UK. Oocyte diameter was also found to have a significant effect on potential fecundity, suggesting a down-regulation of oocyte numbers arising from pre-ovulatory atresia, however, this effect was not apparent in every model tested. Our findings have relevance to the local sustainability of spawning components and thus the regional management of the North Sea sandeel stock.

The endangered patellid limpet Cymbula nigra is present in the extreme western Mediterranean, yet the species has rarely been the subject of study in this region. The aim of the present research is to describe the ecology, distribution and population structure of the species in an area of the Mediterranean coast of North Africa (Ceuta). Results indicate that the species prevails in waters that have an important Atlantic influence. Furthermore, different shell morphologies are distinguished, and in consequence, a statistical analysis is carried out based on morphometric data. Based on maximum shell length, height/length coefficients and shell morphology, a total of three significantly different morphologies are described. Furthermore, considering physical parameters such as height over seawater level and average substratum inclination, juveniles resulted to be clearly segregated from the two other groups. Additionally, no differences were found regarding the topography of the substrate used by juvenile and adult individuals, although the colonized surfaces are significantly smoother than those where Patella ferruginea is present.

A new species of vesicomyid bivalve (Isorropodon nyeggaensis sp. nov.) is described based on shell morphology, from the Nyegga cold methane seep area on the Norwegian continental margin. This is the first description of vesicomyids from the Norwegian Sea and the northernmost record of recent representatives of the family Vesicomyidae. A dispersion of the genus into the Norwegian Sea basin from the north-eastern Atlantic is suggested. A brief description of other macrofauna from methane seep sites at Nyegga is also given.

Improved understanding of the occurrence and spatio-temporal distribution of bivalve larvae holds significant benefits for ecological studies, shellfisheries management and aquaculture. Morphological methods for identification have proved difficult to develop because of the small size of these larvae and similarities in their shape and colour. Molecular methods based on DNA extraction can confirm the presence of a species in a plankton sample, but without sample sorting and individual larval analysis, provide no estimate of larval abundance and are incapable of providing an estimate of larval growth rate. Fluorescence in situ hybridization (FISH) using species-specific DNA probes has the potential to resolve these issues. However, utilization of this technique is constrained by the strong autofluorescence, common in marine larvae. Here we evaluate the effect of eight different fixatives on the autofluorescence intensity of bivalve larvae using fluorescein isothiocyanate (FITC) and Cy3 filters. In addition, fifteen autofluorescence reduction treatments were evaluated and their compatibility with FISH assessed. Relative to fresh larvae, chemically fixed larvae had significantly higher autofluorescence in both filter sets. Larvae preserved by freezing at –80°C exhibited no significant increase in autofluorescence over a 3-year period. Autofluorescence levels were generally lower with the FITC filter set than the Cy3 filter set. For archived larvae preserved in modified saline ethanol and exhibiting fixative-induced autofluorescence, the autofluorescence intensity could be reduced to 20–30% with saturated Sudan Black B and to 30–40% with Chemicon™. Both of these autofluorescence reduction treatments were compatible with subsequent FISH protocols using a FITC-labelled probe.