One juvenile specimen of the sandbar shark Carcharhinus plumbeus was recorded for the first time from the southern Tyrrhenian Sea. The specimen has been collected in an area of the Sicilian coast where trawling is banned except for scientific purposes. Morphometrics and meristics data are given.

A new species of the synallactid sea cucumber genus Pseudostichopus is described, P. aemulatus sp. nov., based on genetic (DNA sequences of the mitochondrial gene Cytochrome Oxidase I [COI] gene) and morphological characters. A comparative molecular study with two other species of the same genus (P. villosus and P. mollis) and from a different family (Isostichopus fuscus) was carried out in order to clarify its taxonomic identity. The nucleotide distance between P. aemulatus sp. nov. and P. villosus and P. mollis is sufficient to support distinct species status. The estimated difference in the number of amino acids, coded for by a partially sequenced COI gene, within the species of the family Synallactidae ranged from 4 to 18. The phylogenetic analysis clearly supports separate species status of these sympatric morphotypes, as indicated by the morphological analysis.

We evaluated experimentally whether distance between patches of the brown alga Sargassum stenophyllum relative to the source of colonizers influenced colonization patterns by (1) mobile epifauna and (2) gammarid amphipods with distinct life habits. Amphipods were the dominant group, commonly dispersing to patches up to 8 m distant from the algal bed, with low densities of other faunal groups. Assemblage structure of both faunal groups and gammarid amphipods on defaunated algae generally converged to that of controls during the experiments in less than eight days. Gammarid amphipods were dominated by tube-dwellers, but free-living nestlers also colonized the available substrate, and both reached control densities during the study. The same pattern was observed for representative species within each group. Colonization rates were related to faunal densities on the algal bed for most groups, suggesting that mobile organisms disperse more to new habitat patches in high density conditions. Thus, species with direct development can rapidly establish new aggregations at favourable sites, and contribute to small-scale heterogeneity in faunal distribution.

A single ovigerous female of Bythocaris cosmetops is recorded from the Bay of Biscay. This specimen is described and illustrated. This rare shrimp was previously known by a single specimen collected off tropical West Africa.

The capture of a specimen of Sphoeroides spengleri (Osteichthyes: Tetraodontidae), 17 December 2000 and 29·7 mm total length, from the Málaga coast (Alborán Sea, western Mediterranean) represents the first record of a new alien species for Mediterranean waters.

This paper details the first recorded instance of the prawn Palaemon macrodactylus in Europe, at the Orwell estuary, Suffolk. The species is native to north-east Asia, including Japan and Korea, and has previously been introduced to other areas outside its natural range. Records of the abundance of caridean species, obtained from routine benthic trawl samples in the Stour and Orwell estuaries, provide a summary of P. macrodactylus' habitat preference in reduced-salinity waters. Consistent catches and records of ovigerous females provide evidence for the stability of the Orwell population. A revised key to British Palaemonidae is also provided.

Two species of corophiid amphipods are described from the ‘Lucky Strike’ hydrothermal vent on the Mid-Atlantic Ridge near the Açores. One species, Bonnierella compar sp. nov. is new to science, the other, Autonoe longicornis has not been reported since the original description of a single female in 1909. Full descriptions are provided of the new species, and of the previously unknown male of A. longicornis.

The growth of the Ficopomatus enigmaticus reefs was measured throughout a coastal lagoon at different temporal and spatial scales (over 24 years, annually and monthly throughout the coastal lagoon). The results show that reef cover increased in the last 24 years, and many neighbouring reefs have coalesced into large platforms. Growth rate varies spatially and temporally. Small reefs grow faster than large ones. Ficopomatus enigmaticus polychaetes living in higher salinity areas show a lower biomass than those living in brackish water areas, and the same pattern was observed for the inter-ring distance measured on the tubes. The results also show that important environmental variables, including salinity, nutrient availability and environmental energy (measured as current speed and depth) may be the most important factors affecting the growth and spread of the reefs.

Caprella spp. (Crustacea: Amphipoda) inhabiting the Sargassum algal community in Otsuchi Bay near unpopulated areas of northern Japan, were collected from 1994 to 2001 and subjected to analysis of butyltin (BT) concentrations. The period from 1994 to 2001 corresponds to four to 11 years after legislation limiting the use of tributyltin (TBT) on small boats and aquaculture facilities was passed in Japan. Butyltin compounds including TBT, dibutyltin (DBT) and monobutyltin (MBT) were detected in all samples of Caprella spp., although the three BTs were not detected in seawater samples collected from the same area between 1997 and 1999. The concentration of total BTs (BTs=MBT+DBT+TBT) in Caprella spp. significantly decreased from 84 ng BTs/g wet wt in 1994 to 7·4 ng/g wet wt in 2001. The concentrations of BTs in Caprella spp., which have a high bioconcentration factor for TBT, are thought to reflect the average concentrations of BTs in the surrounding seawater in the previous few months. The half-life of BTs and TBT in Caprella spp. was 2·38 years and 2·07 years, respectively, which are less than half of that of TBT in seawater based on the national survey of The Ministry of the Environment, Japan. Illegal usage of TBT near the studied area may have decreased due to monitoring of BTs.

Distichopora robusta, the first shallow-water stylasterid coral from the tropical eastern Pacific, is described from the west coast of Panama. The new species is distinguished from all species of Distichopora described thus far by having robust branches and poorly defined pore rows.

The occurrence of morpho-chronological variations was demonstrated in three Australian species of phanerogams, Posidonia australis, Posidonia coriacea and Posidonia sinuosa, which are found living around Rottnest Island (Western Australia). Three chronological parameters were identified: the thickness of dead sheaths, the internodal distance and the regular presence of floral stalk remains. The foliar primary production for these three species, as estimated using the lepidochronology method, is very high since values of 1374, 1811 and 678 mg dw shoot−1 y−1 were recorded, respectively. Rhizome production values range from 70·6 and 376·7 mg dw shoot−1 y−1 for Posidonia coriacea and Posidonia australis respectively. The results obtained are very encouraging and confirm that these morpho-chronological variations are particularly well developed for the genus Posidonia.

A species of the genus Amorphinopsis is described for the first time for the Atlantic Ocean. The new species was described based on the study of 25 specimens, collected in the area of the São Sebastião Channel and its environs (northern sector of São Paulo State coastline) and in the Cabo Frio region (Rio de Janeiro State). The form is massive cushion-shaped, lobate, occasionally encrusting. The megascleres are styles [160–260 (N=20)/5–10 (N=10) μm; length/thickness] and oxeas [150–900 (N=100)/5–18 (N=20) μm]. Amorphinopsis atlantica sp. nov. differs from the other species of Amorphinopsis by its colour, dark-greyish-green with or without yellow tinges on the exposed surface, and the smaller size of its oxeas. Amorphinopsis excavans is the closest species to the Brazilian material, but can still be set apart by a series of smaller traits, such as oxeas and styles never overlapping (the smaller oxea is always larger than the larger style).

Over a period of five years (1997–2002) the euphausiid Thysanoessa inspinata has been recorded in plankton samples from the eastern Gulf of Alaska, as far north as 59°N. Until recently the northern limit of distribution of the species was assumed to be little further north than 50°N but the species is present in oceanic samples off the Alaskan continental shelf throughout the year and occurs regularly in the waters of the eastern Gulf.

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.

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.

Thylacoplethus isaevae, a new species of colonial rhizocephalans, is described from the hermit crab Pagurus trigonocheirus collected in the Sea of Okhotsk, along the coast of Sakhalin Island. The new species differs from other known species of Thylacoplethus by the presence of complex spermatogenic bodies located within the mantle and the significantly larger size of its externae.

The discovery of the association between the sponge Desmapsamma anchorata (Demospongiae: Poecilosclerida: Desmacididae) and the octocoral Carijoa riisei (Cnidaria: Alcyonacea: Clavularidae) on an Indonesian reef enlarges the widespread dispersion of these Atlantic species in the Indo-Pacific area. The species involved and their morphological adaptations resulting from the association are described. When covered by the sponge, C. riisei develops an irregular branching pattern and a dense nematocyst layer where the ectoderm comes in contact with the sponge tissue. The finding of fertile colonies suggests that the Indonesian population of C. riisei is self-sustaining.

This study investigated the synchrony of frond dynamics among patches of the intertidal seaweed Mazzaella parksii (=M. cornucopiae; Rhodophyta: Gigartinales) at local spatial scale. At Prasiola Point (Pacific coast of Canada), the mean synchrony of the seasonal changes in frond density among seven permanent, 100-cm2 quadrats was significant (mean Pearson's r=0·73, with 0·65–0·81 as 95% confidence limits) between 1993 and 1995. This indicates that predicting seasonal trends for non-monitored patches at local spatial scale can be done relatively well based on observations on a limited number of quadrats. The identification of the spatial scales at which seaweed populations covary synchronously will permit minimizing sampling effort while retaining the ability to make valid predictions for non-monitored sites.

Conqueria laevis gen. and sp. nov., a new monothalamous agglutinated foraminiferan, is described from core samples collected in the abyssal western Weddell Sea. The species is characterized by a very elongate, almost cylindrical test that usually follows a more or less curved course and has a single terminal aperture located at the end of a short neck. The wall has a very smooth outer surface and is composed of tiny (<5 μm) agglutinated particles. Very similar and presumably congeneric morphotypes occur at northern hemisphere sites, including Arctic fjords around Svalbard and the Porcupine Abyssal Plain. Molecular phylogenetic analyses, based on small subunit rRNA gene sequences, indicate that the new Weddell Sea species forms an independent lineage branching among monothalamous foraminiferans as a sister group to the clade of Psammophaga.

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.