The occurrence of barnacles and crabs on Caretta caretta specimens found in the waters around Italy was analysed. In the seas surrounding Italy balanomorph barnacles occur mainly on turtles frequenting shallow waters and crabs display a strong west–east gradient. Patterns of turtle distribution and movements are proposed. The abundance of turtle-specific barnacles may be dependent on, and so an indicator of, turtle density.

Three specimens of the spider crab, Maja goltziana, were caught from the southern Adriatic (Mljet Island) and represent the first record of this species in the Adriatic Sea.

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.

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.

A large caprellid amphipod recently discovered at a salmon farm in the Lynne of Lorne near Oban, Scotland, has been identified as Caprella mutica, a species indigenous to north-east Asia. The caprellid population appears to have become established in the last four years at the site with a high abundance of animals occurring year round on the farm nets, mooring ropes and on artificial experimental structures located <10 m from the fish farm. This paper briefly describes C. mutica found in Scotland. Application of Chapman & Carlton's criteria for determining introduced species suggests that C. mutica is non-indigenous to the area.

A new species of pleustid amphipod of the genus Pleusymtes is described from the west coast of Ireland. It was found to be common in association with an Acanthogorgia sp. gorgonian at 725 and 900 m depth on coral habitats in the continental shelf-break areas of the Porcupine Seabight and Porcupine Bank. It is assumed to be a commensal due to its modified pereopod dactyls.

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.

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.

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.

The genetic diversity of the soft-shell clam Mya arenaria from seven locations in Europe (two stations in the southern Baltic Sea (the Gulf of Gdansk) and two in the North Sea (Veerse Meer and Oosterschelde), and three additional stations in the Denmark Straits and Bay of Biscay) was determined using starch gel electrophoresis of allozymes. The results showed a low level of genetic variability and a lack of genetic differentation among the populations studied. Basic polymorphism characteristics calculated for populations from the North Sea estuaries and the Gulf of Gdansk were: He 0·094–0·145, Ho 0·092–0·130, percentage of polymorphic loci 33 (0·95 criterion), mean number of alleles per locus 2·0–2·7. The mean value of FST was 0·0133 and not significant. It is concluded that in spite of a low level of genetic polymorphism the soft-shell clam is a successful colonizer. The genetic homogeneity among the populations reflects rapid population extension, alleles neutrality and a high gene flow.

This paper reports the observations recorded on the arcid clam, Anadara demiri, from its first reporting in the Adriatic Sea three years ago, when its presence only was noted, to the present day when its invasive potential is confirmed. Repeated recruitment events were observed and confirmed by the co-existence of two or more cohorts within the population. Anadara demiri appears to be a year-round spawner with two spawning peaks (late winter and summer). Together with the congeneric invader, Anadara inaequivalvis, it has colonized the external belt of the fine well-sorted sand biocoenosis where they may numerically dominate the benthic community. Anadara demiri appears to have gained full status as a component of the Adriatic Sea coastal benthic community despite its very recent first entry. Numerous features make it a strong competitor among which is the ability, retained into adult life, of attaching, by means of byssus threads to all kinds of hard substrata, particularly to other live molluscs such as the gastropod Aporrhais pespelecani and the bivalves Anadara inaequivalvis and Chamelea gallina. The presence of species actively interfering with A. demiri in various ways (the polychaetes, Polydora sp. and Sabellaria spinulosa, that bore into and foul the shell, respectively, and the predatory asteroid Astropecten irregularis) is discussed.

The occurrence of an area of methane seepage off Chile is reported for the first time. Shell fragments of two species of bivalves of the genus Calyptogena and one species of Acharax were retrieved in dredge hauls from 651 to 934 m depth off Concepción (≈36°S). A large quantity of carbonate blocks was also collected, indicating anaerobic oxidation of methane in the sediment. The accompanying, non-chemosynthetic fauna from one of the hauls was diverse, containing some species new to science. Our preliminary data suggests an assemblage similar in structure to those reported elsewhere, albeit with an important endemic component.

The first occurrence of the alien gastropod Melibe fimbriata in the Taranto marine coastal area is reported. This mollusc was observed on muddy bottoms covered with dense algal beds mainly composed of Chaetomorpha linum, Gracilaria spp. and the invasive chlorophyta Caulerpa racemosa. Occasionally, M. fimbriata specimens were found in proximity to mussel farms. Most specimens of M. fimbriata were observed during diurnal foraging activity and associated with anaspideans species, like native Aplysia depilans and the lessepsian immigrant Bursatella leachii. Melibe fimbriata can be considered a definitively resident species in the opistobranch fauna of the Taranto seas.

The first known occurrence of a naturalized population of Manila clam (Tapes philippinarum) in UK waters is reported. Introduced into Poole Harbour for aquaculture in 1988; by 1994 local fishermen and wading birds began to exploit this northernmost naturalized population in Europe. The licensed fishery currently supports 31 local fishers, landing approximately 250 tn. of clams in 2002. The current distribution of the clam in Poole Harbour, the biology of this naturalized population and the ecological impact of its introduction and fishery, is described.

Samples of shells of the razor clam Ensis directus were examined in order to characterize annually forming shell marks (annuli). Shells from different grounds were aged by naked-eye examination. Back measurements at the identified annuli were used to generate length at age data, to which von Bertalanffy growth parameters were fitted.

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.

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.

Lessepsian migrant Siganus rivulatus is reported for the first time from the Adriatic Sea, substantially further north than its usual area of occurrence in the Mediterranean Sea. Two specimens (111 mm total length [TL] and 149 mm TL) were captured by beach seine on 5 October 2002 off islet Bobara, near Cavtat (southern Adriatic). Morphometric and meristic characteristics of the specimens are provided. The possible explanations of this occurrence are discussed.

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.

Meristic and morphometric data of a specimen of tarpon Megalops atlanticus caught off the Asturias coast, northern Spain, are reported. This is the first record of this species in Spanish waters.