Mytilaster minimus is widely distributed along the rocky intertidal of much of the Mediterranean's coastline and the Adriatic Sea. Populations are, however, threatened by the Lessepsian invader Brachidontes pharaonis that occupies the same habitat and is more tolerant of environmental extremes. This is the first study of the anatomy of M. minimus in relation to its evolution and adaptations towards an intertidal life on the karsted limestone shores that characterize much of the Mediterranean. In most anatomical respects M. minimus is a typical mytilid but is small (<16 mm shell length) and, post-juvenile, greatly deformed concomitant with its niche of colonizing pits in the karsted rocks. It is thus generally squatter, that is, dorso-ventrally flattened, laterally expanded and antero-posteriorly foreshortened in comparison with M. galloprovincialis. A pair of statocysts has been identified in the visceral mass. Most interest, however, resides in the fact the posterior byssal retractor muscles, like the shell, are foreshortened to comprise one paired block and the posterior pedal retractor muscles are situated beneath these not anterior to them as in other mytilids. These adaptations equip M. minimus for a compressed, squat, life in the intertidal karst. In addition to competition from the introduced B. pharaonis in the Mediterranean, M. minimus is facing competitive exclusion from the native Mytilus galloprovincialis that, as a result of intensive and increasing mariculture, is coming to dominate Croatian shorelines. This study is, therefore, prescient in laying the foundations for future research on what is becoming a threatened native Mediterranean species.

Although semi-isolated mangrove lagoons are common in the Caribbean, few studies have surveyed organisms of multiple trophic levels and taxa in these lagoons, which are characterized by a lack of adjacent seagrass and coral-reef habitats. In this study, visual surveys, minnow traps and plankton tows, which were deployed at abutting mangrove prop roots and on macro-algal beds 5 and 15 m away from the prop roots, were used to study assemblages of fish and their potential prey in a semi-isolated lagoon located on Utila, Honduras during the dry season. Assemblages of fish and macro-crustacea differed between the three distances from prop roots, while zooplankton abundances were highly variable and did not follow any distinct distribution patterns. Daytime visual surveys found that large lutjanid (snapper) juveniles, tetraodontid (pufferfish), and some species of brachyurans were more abundant near prop roots. Small lutjanid juveniles were also significantly more numerous near prop roots, but their potential prey, copepods, showed no such difference in abundance. However, 24-hour minnow trap catches found that mean fish abundance (although low) did not differ between near-mangrove transects and transects located in algal beds away from prop roots. Whereas it is well known that mangrove–seagrass habitats play a vital role for fish in open systems, low abundances of organisms in algal beds, particularly in the day time, in this study indicate that algal beds may not be as important to fish in a semi-isolated mangrove lagoon.

Early investigations of the deep-sea fauna of the north-east Atlantic region resulted in many new Sipuncula species being described, notably by such workers as Koren & Danielssen (1877), Théel (1905), Sluiter (1900, 1912) and Southern (1913). Many of these species were erected from single, or few, specimens and some are still known only from the original records.

This paper examines the status of certain species, mostly the seemingly-rare golfingiids described by Sluiter and Southern (see Table 1), the types of which were deposited in the collections of the Irish National Museum, Dublin (INMD) and the Musée Océanographique, Monaco-Ville (MOMV), and presents some new observations and records. The names of taxa follow the classification of Cutler & Gibbs (1985); Nephasoma Pergament and Apionsoma Sluiter, formerly considered as subgenera of Golfingia Lankester, are now elevated to generic rank.

Subtidal macroalgal assemblages differed among islands within the Recherche Archipelago, Western Australia, with respect to species biomass. To investigate whether macroalgal populations were maintained locally, settlement plates were moored in 10 to 15 m depths at a reef sampled for macroalgal diversity, and 20, 50, 100, and 500 m away from the reef. Plates were retrieved after eight months and assemblage differences were compared with distance from the sampled reef. Macroalgal richness decreased with distance from an island assemblage and molluscan richness increased. At 500 m away, the number of algal recruits was negligible and the number of bivalves was relatively high.

Size at first maturity of Adelomelon brasiliana near Mar del Plata, Argentina, was established analysing gonad tissue samples and the secondary sexual characters. Age was determined through growth marks. Gonad matures after development of secondary sexual characters.

Minimum shell length at sexual maturity is 107 mm in females and 102 mm in males. The shell length at which 50% of the animals are mature is 115.1 mm in females and 107.25 mm in males (approximatley 7 years of age). In males, penis matures before testis. All animals are mature beyond 125 mm in females and 115 mm in males, respectively (approximatley 8 years of age). The comparative late sexual maturation in this species makes the population quite sensitive to over-fishing.

This study explored whether the growth and sexual maturity of female John Dory (Zeus faber) differed in relation to hydrographic conditions at sample sites in the East China Sea. John Dory were collected around the margin of the continental shelf from the north-east to south-west waters of the East China Sea, and seasonal changes in spatial distribution were unclear. These probably reflected physiological constraints on salinity, as John Dory are distributed only in waters of high salinity. Thermal gradients along latitudinal lines were evident within sample sites. The northern population was subject to lower temperatures than the southern population during all sampling periods. There were no significant differences in length–age relationships between sampling locations, although the northern population had better body condition than their southern counterparts for a given length. However, northern John Dory matured earlier than their southern counterparts with the same relative condition factor.

The factors potentially leading to the development of periodic hypoxia were investigated based on field studies performed over a series of two years between November, 1997 and November, 1999. This was attempted by investigating both hard and soft seafloor. Descriptive and predictive models were developed that incorporated physical, chemical and biological data derived from the present study and previous work and were used to anticipate future possible crashes of the faunal communities due to hypoxia/anoxia. It was concluded that periodic hypoxia at Ardbear is a natural event caused by several factors to varying degrees. The results of the present study indicate that the major controlling factors for oxygen depletion are the shallow depth of the system, coupled with the development of thermal stratification during periods of calm ambient meteorological conditions of the warmer summer months. In addition, a soft, muddy bottom and highly productive plankton blooms exacerbate conditions in a system already predisposed to hypoxia.

A new bathyal leucothoid amphipod, Leucothoe cathalaa sp. nov., is described and illustrated based on specimens collected at the Le Danois Bank (‘El Cachucho’ Marine Protected Area), southern Bay of Biscay. This species can be distinguished from the other species of the genus Leucothoe by the hardly visible eyes (translucent ocelli, in preserved specimens); antenna 1 with minute accessory flagellum; coxae 1–3 with 2 serrations on posterodistal margin; epimeron 3 posterodistal corner produced, bifid, with one seta between blunt lobes and telson apex pointed without accessory teeth. In live specimens, the eyes are easily visible, each represented as a rounded whitish-pigmented spot. The new species has been found living on fine sandy soft-bottoms between 486 and 574 m depth at the top of the bank. An identification key to the deep Atlantic European species of Leucothoe is provided, as well as ecological and biological comments.

The use of tetracycline marking has enabled the daily production rate of calcareous spicules in the Mediterranean calcisponge Clathrina cerebrum to be measured. Twenty-four hours after starting the experiment newly formed spicules represent about 10% of the total spicule number. No differences in this rate of spicule secretion were detected between the samples tested under light and dark conditions. The growth rate of the tetracycline-tagged spicules in Clathrina cerebrum is similar to that found for other calcispongiae using other methods.

Spicules constitute the skeleton of sponges and are the most important taxonomic character in this group. In calcareous sponges many details of the process of spicule secretion are well known (see Simpson, 1984 for review), particularly their chemical composition and crystallographic structures (Jones, 1955, 1967; Jones & Jenkins, 1970; Ledger, 1976). Ultrastructural studies were carried out on the cellular processes involved in spiculogenesis (Jones, 1970; Ledger & Jones, 1977), but little is known of the rate of spicule secretion. This phenomenon has been studied here by tetracycline marking of newly calcified spicules, triactines. Tetracycline forms complexes with calcium or other metal ions which are easily incorporated into biominerals; consequently it can be used to label the growth of biocalcified structures (Ibsen & Urist, 1962). This method is commonly used in medical research (Urist & Ibsen, 1963; Sandhu & Tonna, 1986; Milch et al., 1957; Van Linthoudt et al., 1991), and has also been employed in studies on biocalcification in marine organisms, such as echinoderms (Gage, 1992) and molluscs (Nakahara, 1961).

In a former paper (1922) it was shown that the pH value of stored sea water decreased owing to the production of carbonic acid by organisms in it, and the oxidisable matter as indicated by this biological method appeared to be higher than the result obtained by oxidation with permanganate, according to various analyses available for comparison. These, however, were not done on the same water, so an attempt was made to determine this quantity on water of the English Channel off Plymouth. As is well known the permanganate method gives results which vary appreciably, according to the conditions of the experiment.

This article reports on four different juvenile reef fish species, Polydactylus virginicus, Haemulon aurolineatum, H. steindachneri and Carangoides bartholomaei swimming along with schools of the caribbean reef squid Sepioteuthis sepioidea. Three different behaviours were observed. This is the first record of this squid species on Brazilian reef habitats. We suggest that this behaviour is mainly related to protection for juvenile fish against potential pelagic predators.

The barnacle cypris larva possesses a pair of laterally placed compound eyes and a median nauplius eye which is tripartite in structure. Concomitant with the metamorphosis to the juvenile is the loss of compound eyes and the nauplius eye separates into its three constituent parts (Walley, 1969). The two dorsolateral components of the nauplius eye come to lie under the rostral shell plates, whereas the ventral component forms the median ocellus which underlies the mantle flaps of the scutal plates at theposterior margin of the adductor muscle (Figure 1).

Crab species had not been exploited until recently in the San Matías Gulf. An experimental trap fishery plan was developed to provide information on the feasibility of their potential extraction. Sampling was carried out using an artisanal shellfish boat in the San Matías Gulf. Nine baited traps, three of each type (cubical, tubular-conical and tubular-pyramidal) were intercalated along a master line. The total number of crabs of each species caught was compared among lines (N=27), types of trap and soaking times (6, 24 and 48 h). A total of 137 traps of 243 traps employed caught crabs. More crabs were caught in the cubical traps than in the other types. Comparisons of numbers of crabs among lines allowed identification of areas having different relative abundances, with an average of 3.56 crabs per trap. The catch of Ovalipes trimaculatus was significantly greater in lines on the 10-m isobath. Two lines, on the 50-m isobath, showed the best results for Platyxanthus patagonicus. The total number of crabs per trap obtained during a soaking time of 6 h was significantly less than the number caught with longer soaking times. Only individuals exceeding 50 mm in carapace width were caught. The size-frequency distributions differed significantly between sexes for the two species, with males larger than females. In O. trimaculatus, males made up 29% of the catch and the remainder was constituted of non-ovigerous females; mean carapace width was 92.93 mm for females and 105.93 mm for males. Forty per cent of P. patagonicus were males (mean carapace width: 99.33 mm). Females bearing eggs amounted to 45% of the total females. Females' mean carapace width was 90.58 mm. Based on the results obtained, preliminary suggestions for management of a potential fishery for these species are made within a precautionary approach.

The distribution of Pectenogammarus planicrurus Reid around the British coast appears to be restricted to a few scattered areas. As far as is known it has only been recorded in three localities.

The first of those is the ‘type locality’, described by Reid (1940), at Saltdean, Sussex. Here the upper region of the shore consists mainly of flint pebbles, the middle shore mainly of sand with patches of flint and chalk pebbles and the lower shore of boulders of chalk on a solid chalk base. Reid found it plentiful under stones near high water mark.

In a brief survey of the south coast beaches, from Brighton, Sussex, to Deal, Kent, in the summer of 1965, P. planicrurus was found in large numbers on the chalk and flint beaches associated with the coastal outcropping of the chalks of the North and South Downs. By far the largest populations were found at Seaford, Sussex, where, unlike Saltdean, the pebbles and gravel extend down to low water and P. planicrurus was not restricted to the upper part of the beach as it was at Saltdean. It appears that the ‘type locality’ described by Reid (1940) does not give a true picture of the vertical range of distribution of the species.

The second locality is at Port Erin, Isle of Man, where Jones (1948) observed P. planicrurus ‘under stones’ between H.W.N. and L.W.N. at Spaldrick on the north side of Port Erin Bay. Jones did not find this species in sufficient numbers to formulate a general idea of its habitat.

Reproductive aspects of the sea cucumber Athyonidium chilensis were studied over a year in Valdivia, Chile, through gonad index (GI) analysis, macro- and microscopic analysis of the gonads, fecundity and size at first sexual maturity estimations. We also explored the reliability of live size estimators for their use in fisheries. Athyonidium chilensis showed continuous gametogenesis and spawning individuals could be found throughout the year. However, spring was the main reproductive time, where an important GI decrease coincided with enhanced spawning activity evidenced through histology. GIs recovered in summer, and new signs of enhanced spawning activity were observed towards autumn (April 2008). GI peaks were observed in August 2007 and March 2008 for females (22.8 and 24.4% respectively) and September 2007 and March 2008 for males (31.9 and 25.9% respectively). Low mean GIs occurred in May and December 2007 for females (15.2 and 11.6% respectively) and May and October 2007 for males (12.7 and 14.1% respectively). Males reached sexual maturity at a smaller size than females (males: 21.2 g, females: 43.7 g eviscerated weight), and mature females showed a high mean absolute fecundity for a species with lecithotrophic larval development (6.31 × 105 ± 1.97 × 105 SD). For fisheries, we recommend a minimum catch size over 237.89 g drained weight to ensure that caught individuals are sexually mature. This study provides relevant information for the conservation and fishery management of A. chilensis. Continuous gametogenesis and high fecundity make this species particularly suitable for aquaculture in southern Chile.

While it is known that the hydroid Clytiajohnstoni (Alder) may get broken off and drift in the plankton (Russell, personal communication), rounding off into pelagic colonies, there is, however, no record of the hydroids Sarsia tubulosa (M. Sars) and Tubularia larynx (Ellis and Solander) living under similar conditions.

Popularly known as blue land crab, Cardisoma guanhumi is heavily exploited as food and considered as an important economic resource in Brazil. In recent decades, the species has experienced a sharp population decline by the loss and/or degradation of its natural habitat and overfishing. The present study aimed to investigate the genetic variation and connectivity among 154 specimens of C. guanhumi sampled along the coast of Pernambuco in five different levels of tropical mangroves conservation. Nine ISSR primers were used for assessing the genetic variation of the species. The genetic diversity observed in C. guanhumi was high reinforcing the condition of a resilient species, indicating a good conservation status of this resource in Pernambuco. The hypothesis of panmixia was rejected in favour of a heterogeneous distribution of the genotypes of C. guanhumi (ФST = 0.19) despite the high gene flow observed in the study region. Such difference could be attributed to the candidate loci being under positive selection and differentially distributed between the geographic regions assessed. The genetic structure showed a pattern of fine-scale genetic structuring better fitted to a model of selection-mediated geographic cline. Cluster analysis and candidate loci under positive selection suggested that the populations of C. guanhumi in the North-central and South coasts of Pernambuco might be different management units and must be managed independently. In conclusion, exhaustion of natural stocks upon which fishing is totally dependent will lead to serious ecological and sociocultural impacts.

The recent establishment of the lessepsian species Leonnates persicus (Annelida: Polychaeta: Nereididae) in Izmir Bay (Aegean Sea) was investigated. A total of four specimens were collected at three stations in December 2001, with two specimens having eggs within their coelomic cavities and parapodia. A re-description of the species together with its ecological and distributional aspects are provided.

Carpet shell clam populations on the Tunisian coastline are susceptible to several microbial pathogen challenges. In this study we report the results of five years' surveillance, conducted from January 2004 till June 2009, for detection of Perkinsosis and brown ring disease (BRD). The survey covered three sites of natural populations of Ruditapes decussatus in a Tunisian lagoon, the North Lake of Tunis. Perkinsosis was detected preferentially in winter periods from the external and marine site, BRD was detected more frequently in the summer periods in a more proximal collection site (in the lake) and was positively correlated with concentrations of heterotrophic Vibrio sp. Our results suggest that several factors other than temperature and salinity might explain spatial distribution variability and natural intensities for these infections in carpet shell clam populations.