The study area for this work includes all the southern edge of the Bay of Biscay, from the north-west Iberian Peninsula to the southern half of the French shelf. The principal aim of this article is to provide a complete overview of the physical oceanography of the area, mainly in its mesoscale aspects, of which there are few published studies, and the implications for early fish life history stages. The results showed the existence of two space and temporal scales for most of the physical processes that occur in the Bay of Biscay, a macroscale for seasonal time periods and a meso and submesoscale for the periods between seasons. The importance of local phenomena, such as upwelling or the variability of the Poleward Current, was observed. The interaction of both scales on these physical processes is discussed and the need for sampling at the submesoscale level to determine the distribution of ichthyoplankton is considered. Moreover, the mesoscale physical oceanography study is essential to improve the knowledge of interactions between strategies and environmental conditions that result in a significant mortality reduction in fish early stages.

A new contribution on spatial and seasonal variability of physico-chemical parameters of the Golfo San Jorge benthic system from autumn 2001 through summer to 2002 is presented. Temperature, salinity, density, oxygen content and chlorophyll-a in bottom water as well as concentration of total organic matter, total organic carbon, total nitrogen, total phosphorus, chlorophyll-a and phaeopigments in sediments were analysed. The origin and nutritional value of the deposited organic matter were also assessed. The results reflect the existence of: (1) a typical temperate water seasonal cycle; (2) a bimodal cycle in the phytoplanktonic production; and (3) seasonal variations in the chemical variables and in organic matter origin in sediments.

Three sectors which geographically correspond with those identified in previous studies were defined: (1) the inner area of the gulf; (2) the areas next to the north and south extremes; and (3) the coastal and south-east part.

Distribution and abundance of the macrobenthic fauna was studied in the intertidal and subtidal soft-bottoms of the Ensenada de San Simón (north-western Spain). Depth and grain size were the most important factors in determining patterns of distribution of the macrozoobenthos. A reduced Macoma community was present in the inner area of the inlet structured in two facies subdivision in the community that does not affect its qualitative composition: the first one was in intertidal areas associated with meadows of the sea grasses Zostera noltii and Z. marina and defined by the dominance of Hydrobia ulvae; the second facies in intertidal sediments was characterized by the dominance of Tubificidae and nematodes and Pseudopolydora paucibranchiata. The poverty of these bottoms in number of species can be due to salinity fluctuations and human activities developed in the area. Subtidal bottoms were characterized by a Syndosmya(=Abra)alba community. Two facies were detected: one facies located in shallow subtidal bottoms with H. ulvae and Thyasira flexuosa as characteristic species, and a second facies in deeper areas, characterized by the polychaetes Ampharete finmarchica, P. paucibranchiata, Aphelochaeta marioni, Melinna palmata and Paradoneis lyra.

The benthic diversity of the soft bottoms in the Taranto Seas (Mar Grande and Mar Piccolo) (eastern-central Mediterranean Sea) was studied during July 2002. Quantitative samples were taken using a Van Veen grab and granulometric analysis of the sediment was carried out. A total of 131 species were identified. Molluscs and annelids made up 77% of the species and 87% of the individual number. Data from these two groups were used for hierarchical clustering and multidimensional scaling. The diversity was calculated using the rarefaction method. Two main benthic species assemblages were identified. The first corresponded to the stations characterized by pelitic sediment and located in the Mar Piccolo, the second was made up by the stations with pelite with increasing percentages of sand and distributed in the Mar Grande. The first assemblage consisted of species that usually live on muddy bottoms rich in organic matter; the second consisted of a greater number of species, usually occurring on different types of bottoms. Diversity was found to be higher in the Mar Grande than in the Mar Piccolo, indicating that physico-chemical alterations of the environment probably play a leading role in controlling community structure.

During a survey of the marine rotifers of the Northern Adriatic Sea, Italy, we found a total of 20 taxa, including a new species of Lecane. This novelty, Lecane insulaconae sp. nov., occurred in the interstitial area of sandy sediment in the outlet of the Isonzo River, at a salinity of 30‰ and is therefore the first exclusively marine representative of this diverse (~200 species) genus. It is characterized by unique sets of anterolateral projections on the ventral and dorsal lorica. Here, we present the description of the species, together with scanning electron microscopy pictures of trophi of this and some other species, and an account of the marine rotifers encountered during the survey.

Morphological abnormalities were observed in a population of the stauromedusa Haliclystus auricula in southern Chile. A total of 144 abnormal specimens was observed out of 3790 Stauromedusae sampled. The following abnormalities are described: individuals lacking arms (73%), with more than eight anchors (11%), more than eight arms (8%), lacking anchors (4%) and one individual with tentacles in abnormal locations. An individual with two peduncles, one with two mouths and one twin-like individual are recorded for the first time in this species. Their possible causes are discussed.

The composition and spatial distribution of the polychaete fauna on the subtidal soft sediments of the Ría de Aldán (Galicia, north-western Spain) were studied by means of quantitative sampling and multivariate analysis. The faunal distribution was mainly conditioned by a sediment gradient defined by decreasing grain size, from the mouth towards the inner margins of the ría. The coarse and medium sand fauna was mainly dominated by pisionids, spionids and syllids. Finer sediments (fine sand to mud) showed a greater abundance of paraonids, spionids and cirratulids and deposit feeding species. The greatest number of species and diversity were found in coarse sediments.

The eunicid polychaete Marphysa sanguinea was until recently believed to be a cosmopolitan species, with a distribution ranging from the south-west coast of England to the Pacific coast of America, and New Zealand and Australia in the western Pacific. However, there are many morphological and ecological inter-population differences that render the definitive identification of these numerous populations difficult. The recent designation of a neotype, together with a more detailed morphological description of specimens from the type locality in south-west England, has allowed the concept that M. sanguinea represents a series of cryptic species, to be investigated by examining populations of species previously referred to as Marphysa sanguinea. A new species Marphysa mullawa was described from Moreton Bay Queensland, Australia. In this paper we describe a new species from the western Cape of South Africa which has previously been referred to as ‘Marphysa sanguinea’, using an integrative approach combining morphological data, RAPD-PCR analysis and a study of the sperm ultra-structure. The South African species is a popular bait animal for local sea anglers and is heavily exploited throughout the western Cape. The RAPD-PCR analysis also demonstrates that populations referred to as ‘Marphysa sanguinea’ from other geographical locations studied have distinct genetic pools, providing further evidence that Marphysa sanguinea is not a cosmopolitan species and consists of a suite of cryptic species.

Previous observations in the St Lawrence Estuary (eastern Canada) suggested that larvae of intertidal barnacles (Semibalanus balanoides) would settle almost exclusively inside crevices on shores that are scoured by sea ice every winter. It was suggested that the strong ice scour in winter on that coast (which removes organisms outside of crevices) would select for such a larval behaviour. We tested the generality of this pattern by sampling other ice-scoured shores within the Gulf of St Lawrence system. In particular, we surveyed a shore in Nova Scotia where exposed habitats (subjected to strong ice scour in winter) are interspersed with sheltered habitats (which suffer milder ice scour). Such a topographical complexity might allow for the coastal larval pool to contain a proportion of larvae that have no particular settlement preference for crevices, as selective pressures for such a behaviour would be minimal in ice-sheltered habitats. Consistently with this notion, barnacle recruits (which appear after the winter ice melts) occurred abundantly both inside and outside of crevices across the shore in the spring seasons of 2005 and 2006. Average recruit density on rocky surfaces ranged between 337 and 588 recruits dm−2, depending on the habitat. It is therefore possible that barnacle recruitment patterns on ice-scoured shores may be affected indirectly by the structural complexity of the coast.

This one-year study investigated spatial and temporal variations in the abundance and biomass of the pink shrimp species, Farfantepenaeus paulensis and Farfantepenaeus brasiliensis, in the Conceição Lagoon, southern Brazil (September 2003–August 2004). The influence of salinity, water temperature, and rainfall on shrimp distribution was evaluated. Shrimps were caught monthly at three areas within the Conceição Lagoon (Canto, CA; Centro, CE; and Costa, CO). A total of 744 shrimps were sampled, with F. brasiliensis being the dominant species. The two penaeid species were present throughout the year and significant differences were observed between seasons, with F. paulensis being more abundant during the summer and F. brasiliensis in the autumn, suggesting differential migration timing to the sea, differences in recruitment time and an ontogenetic temporal partitioning. Farfantepenaeus paulensis exhibited a homogeneous spatial distribution, whereas F. brasiliensis was more abundant in CE and CO, suggesting that habitats in this coastal lagoon are heterogeneous. Among the abiotic factors, temperature and salinity seemed to be important variables in defining seasonal and spatial patterns, respectively, of the abundance of F. brasiliensis.

Caridean shrimps display a variety of sexual systems including gonochorism and various forms of protandry but rarely simultaneous hermaphroditism. Protandric simultaneous hermaphroditism (PSH) has thus far only been demonstrated in the genus Lysmata. The first report of simultaneous hermaphroditism in a caridean shrimp was with Exhippolysmata ensirostris. However, this was not confirmed, since this species was also considered to be strictly protandric. Therefore, inconclusive results about this species' true sexual system led us to examine Exhippolysmata oplophoroides. Mating between female phase individuals resulted in successful spawning, embryonic development and hatching of viable larvae. Furthermore, we have confirmed that this species is not capable of self-fertilization. Juveniles reared in the laboratory matured in a similar manner to that of Lysmata. Data were limited due to the loss of all individuals to a Vibrio infection. However, the results obtained in this study conclusively affirm functionally that PSH occurs outside the genus Lysmata, in E. oplophoroides. Theories examining the evolution of PSH within decapods must be re-examined in light of the present data.

The present work reports the existence of parasitic castration induced by the bopyrid isopod Argeiopsis inhacae parasitizing the branchial chamber of female Stenopus hispidus. Parasitized and unparasitized females of S. hispidus displayed similar intermoult periods (14 ± 2 d) and exhibited similar mating behaviours. However, despite exhibiting typical mating behaviour, parasitized females were never able to produce any egg clutch when paired with unparasitized males; neither displayed the typical ‘dorsal bright green spot’ evidencing the presence of large vitellogenic oocytes. The idea that bopyrid infections generally lead to the ‘reproductive death’ of the decapod host is reinforced and the apparent existence of a heavily sex-biased infection towards females in S. hispidus may just be a consequence of the still limited number of surveyed specimens.

The gastric mill on the genus Cyrtograpsus (Varunidae) has not been described previously. A morphological comparative study of the gastric mill ossicles within its species (C. angulatus, C. altimanus and C. affinis) was carried out. This research attempts to give new evidence to validate the existence of these three species and to serve as a guide to identify them. Urocardiac (dorsal median tooth shape), zygocardiac (shape and number of ridges and molar processes—cusps and plates—and their arrangement in the lateral teeth) and pectineal (number and shape of accessory teeth) ossicles, and cardiopyloric valve descriptions and comparisons are based on microscopical, stereomicroscopical, scanning electron microscope observations, and digital images. Morphological differences found in zygocardiac (lateral teeth) and urocardiac (dorsal-median tooth) ossicles allow to identify species. Considering these ossicles morphology in C. altimanus and C. affinis it can be concluded that the studied specimens belong to a single species as stated in morphometric and molecular comparative studies of the above species. These new data validate the existence of only two species (C. affinis and C. angulatus). This information will also be useful to recognize the species in the stomach content of their predators throughout the ossicles morphology.

The gametogenic cycle of the banded murex, Hexaplex (Trunculariopsis) trunculus, from the Ria Formosa lagoon (Algarve coast, southern Portugal) was studied through macro- and microscopic analyses of the gonads during a 1-year study period (March 2003–February 2004). The overall samples presented a balanced sex ratio, with males dominating among smaller individuals and females predominating in larger size-classes. The gametogenic cycle of T. trunculus in the Ria Formosa lagoon comprised an extensive period of gonadal activity, with the simultaneous occurrence of distinct developmental stages of gametogenesis in both sexes almost year-round, and with males invariably presenting gonads in more developed stages of gametogenesis than females. Spawning occurred mainly from May to June 2003, apparently triggered by the rising seawater temperature during spring. Due to the extensive period of gonadal activity, T. trunculus exhibited a short resting phase that occurred simultaneously in both sexes between June and August 2003 and coincided with the period of warmest seawater temperatures. Considering these findings, a closed season in the fishing activity should be implemented during the main spawning period of T. trunculus (May and June), in order to protect the female broodstock and collective spawns.

The larval shell morphology of 10 bivalve species of the family Mytilidae (Adula falcatoides, Crenella decussata, Crenomytilus grayanus, Modiolus kurilensis, Musculista senhousia, Mytilus coruscus, Mytilus galloprovincialis, Mytilus trossulus and Septifer keenae, and an unidentified species Mytilidae indeterminate) from the Sea of Japan is described. The following morphological features were comparatively examined: larval shell outlines including shape and size of umbones, and anterior, posterior and ventral margins, hinge morphology, ligament location, sculpture, colour, and eye-spot outlines. Some dimensional parameters of larval shells are given. The time interval of occurrence of larvae in the plankton, water temperature in this period, and shell length of competent larvae are presented. It is demonstrated that, in spite of sometimes similar external morphological characters, identification of mytilid larvae creates no difficulties if all distinguishing characters are used.

The blue mussel, Mytilus edulis, and the Mediterranean mussel, Mytilus galloprovincialis, occur widely over much of northern Europe, and wherever they are sympatric they hybridize. The hybrid zone is large, ranging from western France to the north of Scotland, and is spatially complex, containing a mixture of pure, hybrid and introgressed individuals. Results from an Irish study in 1981, using partially diagnostic allozyme markers, indicated that mussels on the Irish Sea coast were solely M. edulis, but on Atlantic wave-exposed shores, and to a much lesser extent on wave-protected shores, mussels comprised an interbreeding mixture of M. edulis and M. galloprovincialis. In this study mussels were analysed from 20 locations on Irish coasts, using the Me15/16 nuclear DNA marker. The results showed a high frequency of M. galloprovincialis (0.378 ± 0.198) and hybrid (0.429 ± 0.175) genotypes, and correspondingly low frequencies of the M. edulis genotype (0.194 ± 0.107) at both exposed and sheltered locations on Atlantic coasts, indicating no apparent advantage for the M. edulis genotype at wave-protected sites. Mytilus galloprovincialis was virtually absent from the Irish Sea. Mussels in this area may be a self-recruiting population of M. edulis due to thermal front development at the northern and southern entrances to the Irish Sea in late spring, thereby preventing an influx of spring-spawned Mytilus larvae. The apparent change in the genetic composition of mussels on Atlantic coasts since the early 1980s could be related to climate change, or to aquaculture practice in Ireland whereby mussels from exposed shores are used to seed ropes in wave-protected bays and estuaries.

An expanded description of a little-known arctic species Montacuta spitzbergensis from the Sea of Okhotsk with new data on its morphology, ecology and geographical distribution is given. This is the first record of M. spitzbergensis from the north-western Pacific. It differs from other species of Montacuta in its large (to 8.4 mm), elongate–ovate, thick shell with wide, slightly curved hinge plate, wide, short, and shallow resilifer, and weakly developed external ligament. This species occurs in the Arctic Ocean (Spitsbergen, Barents, Kara, Laptev and Chukchi Seas) and the Pacific Ocean (Sea of Okhotsk) at depths from 9 to 232 m at a bottom temperature from −1.62°C to +2.50°C. The hinge structure of the type species of the genera Montacuta and Tellimya is also discussed.

The metazoan parasite community of Cerastoderma edule was studied in the southern geographical range of the host (the coastal lagoon Merja Zerga, Morocco). A total of 11 metazoan species was found in cockles. Nine of these were trematodes using cockles as either first intermediate host (three species) or second intermediate host (six species). In addition, two other endo-metazoan species (Pinnotheres pisum and Paravortex cardii) were recorded from cockles in the studied lagoon. All the observed metazoans in cockles from Merja Zerga have previously been recorded at sites north of Africa.

Up to 10% of the cockles in the studied size-groups were first intermediate hosts to castrating parasites (Gymnophallus choledochus, Labratrema minimus and Monorchis parvus). Among trematodes having metacercariae in cockles (second intermediate host) Meiogymnophallus minutus was the most widespread as it was observed in all cockles from all the examined habitats in the lagoon and it occurred in record high intensities. Different sub-communities of the trematode fauna using cockles as second intermediate host could be identified (subtidal vs intertidal associations).

The richness and species composition of the macroparasite community in cockles from Morocco are discussed in relation to patterns seen in cockles from other sites along their geographical range. Migratory fish and waterbirds (final hosts) are generally responsible for the large scale spread (latitudinal spread) of trematodes. However, the distributional patterns of involved intermediate hosts in the life-cycles of the different trematode species in cockles are determining the richness and species composition patterns seen in cockles at shallow water sites along the east Atlantic shoreline.

Egg masses, juveniles and adults of the gastropod Palio dubia were found in shallow rocky habitats of eastern Canada dominated by the bryozoan Eucratea loricata. Multiple-choice experiments and direct field observations revealed that P. dubia prefers to feed on E. loricata. Courtship, copulation and egg-laying as well as hatching of P. dubia were closely related to the lunar cycle. Reproduction was preceded by increased pairing and aggregative behaviour. The duration of embryonic development in the capsules was 10–15 d. After hatching, most veligers were retained within the bryozoan branches during their pelagic phase (1–3 d). In multiple-choice experiments, settlement occurred preferentially on the bryozoan E. loricata. In the absence of the preferred substratum, the larvae continued to swim and died after a period that never exceeded 8 d. Juveniles remained associated with the bryozoans on which they settled and reached the adult size in ~3 months.

During biological sampling of hydrothermal vents on the East Pacific Rise, the manned submersible ‘Nautile’ caught the first female of the endemic cephalopod Vulcanoctopus hydrothermalis. The specimen caught at the vent site Gromit (21°33 66′S, 114°17 98′W at 2832 m depth) is described here in detail and an amended diagnosis of the species proposed. The external morphology, measurements and internal structure resemble that of males of this species. One of the most remarkable characters is the lack of spermathecae and the absence of apical filaments in the oocytes to provide a site for sperm storage. It is suggested that some species of the genera Benthoctopus and Bathypolypus would be the most suitable octopod ancestor of V. hydrothermalis.