Distribution and structure of intertidal macrobenthic communities in the Zwin nature reserve, a lagoonal inlet consisting of marsh and tidal flat habitats, was investigated using univariate and multivariate analyses. Macrobenthos community structure was related to environmental characteristics and discussed in the framework of the implemented extension of the nature reserve.

Based on explorative multivariate techniques, five different sample groups (SGs) were distinguished, which were, in general, located in different habitats of the Zwin nature reserve. The ecologically most important SGs consisted of the highest macrobenthic density, diversity and highest densities of Nereis diversicolor and Scrobicularia plana; these important prey species for wading birds and fish occurred in the deep tidal inlet channels. This habitat was characterized by fine to medium sand sediment and strong tidal currents, guaranteeing water renewal at each high tide. Other SGs were found in less and erratically submersed and thus stressed areas (i.e. tidal pond, salt pans and shallow flats). These assemblages were characterized by typical r-strategists (i.e. Capitella capitata and Polydora cornuta) and typical supralittoral, mobile species (i.e. Orchestia gammarellus and Collembola spp.). Being ecologically most important, the extension of wide, tidal creeks should be a prime target within the future development and management of the nature reserve.

The trophic composition of macrobenthic communities in intertidal and subtidal soft-bottoms of the Ensenada de San Simón (north-western Spain) was found to be related to a number of environmental variables. Distribution and abundance of trophic groups have been studied, to provide essential baseline information for monitoring the area, after its designation as a Natura 2000 Special Conservation Zone. Analyses of trophic data showed a numerical predominance of the herbivores in the inner part of the inlet, while sites at the oceanic-influenced area were numerically dominated by surface-deposit feeders. These dominances were mainly due to Hydrobia ulvae in the intertidal area and to polychaetes at the subtidal one. Both univariate and multivariate statistical analyses showed that the sediment composition (organic matter and silt–clay contents) and temperature of the bottom water influenced the benthic macrofauna and were correlated with their trophic composition, abundance and distribution.

The baited remote underwater video technique (BRUVS) was used to compare fish assemblages at three sites with different habitat characteristics: sandy bank (SB), rock reef (RR) and degraded coral reef (DCR) in Port Essington, Garig Gunak Barlu National Park, Northern Territory, Australia. The Carangidae family dominated, representing 35% of all recorded fish. The highest species number was recorded at RR followed by DCR and SB. The highest total fish number was recorded at DCR followed by SB and RR. Fish assemblages from all three sites are clearly different at high confidence level, but still overlapping and higher overlapping was found between SB and RR. Fish assemblages at all three studied sites contained some coral-associated species, fish fauna was less rich compared to coral reefs in the mouth of the bay and fish assemblages were noticeably different from typical coral fish communities. None of the fish assemblages at studied sites were presented by the ‘pure’, single habitat-associated association of species—at all three sites fish communities were a mixture of fish with various habitat preferences. Reef-associated species have a larger proportion at DCR and at RR their habitat complexity was higher; still soft-bottom habitat fish make substantial fractions in fish assemblages at both DCR and RR. Similarly, fish usually identified as ‘reef associated’ were found in notable proportions on SB. Fish with wide distribution and low selectivity in habitat preferences comprised a significant part in fish assemblages at all studied sites. In this study the BRUVS technique worked well in the area where diving visual surveys were impossible to implement because of high water turbidity. Another advantage of this method is the non-impact nature of visual survey; they can be used in long-term monitoring of fish assemblages at reference sites.

Adults of Pseudopolydora rosebelae sp. nov. inhabit silty tubes on muddy bottoms in shallow water in southern Brazil, states of São Paulo and Rio de Janeiro. They are rare and extremely delicate, attaining 20 mm long for 55 chaetigers. The worms are distinctive by their colourful yellow and black pigmentation on the anterior part of body and palps, prominent transverse hood on the dorsal anterior edge of chaetiger 3, and lack of coloured respiratory pigment in blood. Of 12 examined individuals, all were females. Oogenesis is intraovarian; oocytes develop from chaetigers 14–15 to chaetigers 24–36. Recently laid oocytes were about 150 μm in diameter, with embryos and developing larvae found in capsules inside female tubes in March–June. Broods comprised up to 23 capsules with 400 propagules. Capsules were joined to each other in a string and each attached by a single thin stalk to the inner wall of the tube. Larvae hatched at the 4-chaetiger stage and fed on plankton. Pelagic larvae are unique among Pseudopolydora in having large ramified mid-dorsal melanophores from chaetiger 3 onwards. Competent larvae are able to settle and metamorphose at the 15-chaetiger stage, but can remain planktonic up to 18 chaetigers. They have one pair of unpigmented ocelli and three pairs of black eyes in the prostomium, unpaired ramified mid-dorsal melanophores on chaetiger 1 and on the pygidium, ramified lateral melanophores on chaetigers 5–10, prominent yellow chromatophores in the prostomium, peristomium, on dorsal and ventral sides of chaetigers and in the pygidium. Branchiae are present on chaetigers 7–10, and gastrotrochs are arranged on chaetigers 3, 5, 7 and 12. Provisional serrated bristles are present in all notopodia, and hooks are present in neuropodia from chaetiger 8 onwards. Two pairs of provisional protonephridia are present in chaetigers 1 and 2, and adult metanephridia are present from chaetiger 4.

A new thecideide brachiopod species, Thecidellina meyeri, is described from the southern Lesser Antilles (Aruba, Bonaire, Curaçao), Caribbean Sea, with unique morphological characters which clearly separate it from all other described species of Thecidellina in the region. A virtually complete series of ontogenetic stages is recorded, providing insight into the plasticity of shell development during growth in thecideide brachiopods and offering a well-defined standard for comparison with fossil material. Study of the soft tissue suggests that T. meyeri is dioecious, which contradicts the idea of Thecidellina to be hermaphroditic. The limited distribution and the unexpectedly high species diversity within the genus Thecidellina in the Caribbean region support the idea of allopatric speciation due to limited dispersal ability.

Studies of recruitment dynamics in meroplanktonic organisms are dependent on the correct identification of each ontogenic stage of each species. This is particularly difficult when studying the larval stages, which are not easy to identify due to their lack of resemblance to conspecific adults and their high degree of similarity with congenerics at the same stage of development. This is the case with the crustacean megalopae of the genus Cancer along the coast of the south-eastern Pacific. This fact represents a serious limitation on ecological studies of populations of these species which constitute a heavily exploited local resource. In this study we describe in detail field collected megalopae larvae of three sympatric crab species of the genus Cancer(C. edwardsii, C. setosus and C. coronatus). As a result of this analysis we were able to identify easily visible diagnostic characters which allow the species to be distinguished from one another. The megalopae were easily distinguished by the form of the cheliped and the presence of spines on these. Cancer edwardsii has an elongated globulose cheliped, whereas C. coronatus has a subquadrate one. Both species possess a prominent ischial spine, which is absent in C. setosus. We corroborated the utility of these diagnostic characters by comparing the COI gene sequences of mitochondrial DNA of larvae identified by morphology with sequences taken from samples of the adults of all species of Cancer found in the region. We discuss the morphological variations between larvae found across the region (i.e. at sites separated by more than 800 km) and between megalopae obtained from the field versus those cultivated in the laboratory. We conclude that the simultaneous use of morphological and molecular tools for identification of decapod larvae appears useful for the study of cryptic species.

Community structure and vertical distribution of oncaeid copepods were investigated at an offshore site in Tosa Bay, southern Japan. Samples were collected with a 0.063 mm closing type net from eight discrete layers between the surface and 500 m depth in August and November 2005. A total of 45 species and three form variants belonging to the genera Triconia, Oncaea, Spinoncaea, Conaea and Epicalymma were identified. The greatest number of species was consistently found in the lower epipelagic zone, at 50–100 m. The vertical distribution patterns of oncaeid copepods were similar between August and November, with the highest abundances in the upper epipelagic zone above the thermocline. The oncaeid maxima corresponded with the depth where appendicularians occurred in high numbers. Dominant species in the water column (0–500 m) were O. venusta small form, O. media, O. scottodicarloi, O. waldemari, O. zernovi, O. tregoubovi, S. ivlevi, S. tenuis and T. conifera. The vertical succession of species composition was almost the same between August and November, although several species showed a downward shift of their depth-range to some extent in November. The oncaeid copepod community could be differentiated into three distinct groups according to the depth layers, each corresponding to different hydrographic conditions in the water column.

Morphometry has been used in the investigation of the common shrimp Crangon crangon subpopulation structure at a local scale (100 km) around the UK. In the present study C. crangon populations were sampled over the whole distributional range from northern Norway to the Mediterranean and Black Sea to test whether the same method could be applied to describe subpopulation structure at a much larger scale (1000 km). Spatial variability in morphometric characters was determined by sampling 25 locations across the distributional range. In addition, the temporal variability in morphology was studied at 4 sites (Bodo, Norway; Wadden Sea, The Netherlands; Minho and Lima estuaries, Portugal). Contrary to expectations, temporal variability was observed in three of those sites resulting in an inability to distinguish between populations at the local scale. However, the large scale subdivision of shrimp populations from the Adriatic, Black Sea, Mediterranean and Atlantic were clearly identified. It is concluded that, while there are clear morphological differences between major zoogeographical zones, at a local scale, subpopulations frequently cannot be identified because of individual variability.

Seasonal growth pattern and reproductive biology of the Baltic prawn, Palaemon adspersus, were studied in the southern Black Sea between February 2002 and January 2004. The seasonal von Bertalanffy growth parameters, computed from monthly length–frequency distributions, were estimated as L∞ = 62.99 mm TL, K = 1.190 year−1, C = 0.815, and WP = 0.847 for females and as L∞ = 49.63 mm TL, K = 1.085 year−1, C = 0.011, and WP = 0.407 for males. Growth performance index of females (Φ′ = 3.67) was greater than it was for males (Φ′ = 3.43). Based on latitudinal gradients, water temperature negatively affected Φ′ of P. adspersus. Sexual dimorphism in size was evident, females being larger than males. This typically shallow water species was observed in water depths as deep as 30 m. Compared to shallower water depths, larger individuals were observed in deeper water depths. The size at sexual maturity for females (TL50) was estimated as 53.60 mm TL. Ovigerous females were recorded from March to August and juveniles appeared in the benthic population in August. Ovary development was related to photoperiod and occurrence of ovigerous females was linked to increased water temperature.

A total of seven poorly known species of the genus Asterocheres, the largest genus of the family Asterocheridae, are redescribed based on material deposited in the Natural History Museum of London. Among the material available, there were specimens of both sexes of A. bulbosus, A. ellisi and A. rotundus; the dissected holotypes for A. hongkongensis, A. indicus and A. ovalis which have no other specimens; and only cotype of A. micheli, turned out to be lost. Some taxonomically important appendages of these species are described and illustrated for the first time. Furthermore, discrepancies have been observed in: (1) the general shape of the body; (2) the antennule segmentation; (3) the omission of some elements in various oral appendages; and (4) the segmentation of the mandibular palp. These redescribed species were then compared with their closest congeners.

Characteristics of the second gnathopod are traditionally used to distinguish between species of caprellid amphipods. However, these distinctions are often subjective and can be variable within a species. Geometric morphometrics were used to quantitatively assess shape variation of the second gnathopod propodus of three species of caprellids in North America, including the non-native Caprella mutica. Gnathopod shapes of C. mutica specimens from different latitudes revealed distinct morphologies; the factors responsible for the shape variations are unknown. Allometric change of propodus shape was observed in C. mutica. Larger individuals showed a wide array of possible propodus morphologies. Despite this variability, there were clear differences between large specimens of C. mutica and two species native to North America: C. alaskana and C. kennerlyi. The use of geometric morphometrics and the thin-plate spline method can serve to both complement descriptions using traditional keys and aid in identification of non-native species in novel geographical regions.

We describe the digenean fauna of one of the dominant intertidal hosts, the common cockle Cerastoderma edule, in terms of biomass, off north-eastern Atlantic shores. Using published and unpublished literature we have prepared an identification key and provide an up-date of the large-scale distributional patterns of digenean species of the common cockle. At least sixteen digenean species, belonging to seven families, use cockles as intermediate host. Among these species two utilize cockles as first intermediate host only, whereas two species utilize cockles as both first and second intermediate host. The remaining eleven species have cockles as their second intermediate host. Water birds and fish are the definitive hosts to twelve and four species, respectively.

Cockles are infected with digeneans along the latitudinal gradient from southern Morocco to the western region of the Barents Sea often with high infection levels. Whereas some of these digenean species occur along most of the latitudinal gradient others show a more restricted northern or southern distribution mostly caused by an underlying latitudinal gradient of host species.

Knowledge of digenean species and their large-scale distribution pattern may serve as a baseline for future studies dealing with the effects of climate change on parasite–host systems. For such studies the cockle and its digenean community could be an ideal model system.

Beach filling activities were conducted along the Mar del Plata coastline, Argentina, with sediments dredged from the harbour mouth between November 1998 and April 1999. We determined the percentage of imposex of Olivancillaria deshayesiana before, during and immediately after beach filling. The current situation (2005–2007) of imposex incidence was compared between populations from Mar del Plata and Mar Chiquita, a less impacted area. In addition, we evaluated differences in shell shape and body weight between females with and without imposex. The percentage of imposex was significantly higher during (85.3%) and after (73.9%) beach filling than before it (31.0%). No differences in body weight were found in the female population but shell length was significantly lower in females with imposex. As expected, the Mar Chiquita population showed no signs of imposex. This is the first report of imposex in beaches nourished with sand dredged from the port. Our results highlight the importance of analysing more carefully the sediment before beach filling. On the basis of the high level of imposex recorded near the port of Mar del Plata, O. deshayesiana can be used as a biological indicator of marine contamination with butyltin compounds.

In gastropods, variation in shell morphology can be caused by the action of several biotic and abiotic factors. While much of this variation is seen in comparisons between different sites or populations, there is also substantial variation in shell morphology among individuals living side by side. We investigate the effect of trematode parasitism on both intra- as well as inter-site variation in the morphology of the New Zealand whelk Cominella glandiformis. We found that both infection by the trematode Curtuteria australis and site of origin had significant effects on several morphometric dimensions of the snail shell, with some interactions between the two factors. On its own, infection by C. australis accounted for 20 to 60% of the variance in shell morphology, depending on the dimension measured. Infected snails also had smoother shells, with less prominent ridges, than their uninfected conspecifics. Other trematode species, infecting whelks at much lower prevalence, also had impacts on shell morphology, but not necessarily in the same direction as C. australis. Overall, parasitism may be an important factor in explaining intra- and inter-site variation in snail phenotype, with potential repercussions for snail populations and their interactions with other community members.

This paper describes the organism–organism relationship between a bivalve host and larval digeneans. The studied population of the stout razor clam Tagelus plebeius from the mixohaline Mar Chiquita lagoon (37° 32′S 57° 19′W) showed 100% of prevalence of infection by a larval digenean (metacercaria) of the family Gymnophallidae. The larvae occupied the extrapallial space just below the hinge of the bivalve. The tissue reaction against larval digeneans by T. plebeius consisted of hyperplasia and metaplasia of the outer layer of the mantle epithelium adjacent to parasites, forming an invagination to generate a sac that surrounded gymnophallid larvae. According to the intensity of infection, each sac progressively enlarged to harbour a variable number of larvae. In highly infected clams, a great number of sacs are formed. Eventually, the older sacs containing larvae may become closed, losing their communication with the extrapallial space and sinking into the dorsal part of the visceral mass. Larvae within sacs grow and remain alive until they reach an appropriate definitive bird vertebrate host. Older lesions commonly showed remains of dead larvae which had undergone resorption. As a result, an orange to brownish amorphous material accumulated in the space once occupied by the larvae leaving conspicuous orange marks on the inner surface of the valves. In some cases, calcifications in the form of pearls or blisters were observed.

The cuttlefish (Sepia officinalis) is the most important traditional fishing activity in the Sado estuary. In order to analyse the spatial and temporal distribution patterns and to study the reproductive cycle of this species, twenty sampling areas were towed along the estuary on a monthly basis from May 2001 to April 2002. The higher densities were obtained in summer and autumn in the lower and southern area of the estuary while spring showed the higher biomass. Mature individuals prevailed in the inner zone of the estuary during spring while juveniles were dominant in autumn and concentrated in the lower part of the estuary. Almost all individuals leave the estuary during winter. The weight–length relationship was significantly different according to sex, being females heavier than males for individuals larger than 106 mm. Sex-ratio was similar to 1:1 in every season. Females had high values of gonadosomatic index during the spawning season with a major peak in June, while males showed similar values throughout the spawning season. The length at first maturity was estimated at 80 mm mantle length (ML) for females and 59 mm ML for males. In the Sado estuary only one generation of cuttlefish breeders were found with an average of 110 mm ML for males and 122 mm ML for females, which is consistent with breeders in their first year.

This study presents the first extensive investigation of echinoderm distribution in the area of mobile bottoms in the open part of the northern and middle Adriatic Sea. Five hundred and eighteen bottom trawl hauls were performed at 56 predetermined permanent stations along ten transects over different sediment types, at depths of 10 to 430 m. A total of 34 species of Echinodermata were identified (9 from the class Holothuroidea, 12 from the class Asteroidea, 4 from the class Ophiuroidea and 9 from the class Echinoidea). The list of the species, together with data on depth and sediment distribution, and the stations where individual species were found, are presented.

Mar Chiquita, an irregularly shaped brackish-water coastal lagoon, is located in the Buenos Aires province of Argentina and considered since 1996 by the Coordination Council of the Man and Biosphere Program of UNESCO as a World Reserve of Biosphere. The present paper aims to study both the spatial and temporal variation of fish composition in this coastal lagoon and the influence of some environmental variables on the relative abundance of the main fish species. Monthly sampling surveys over a two-year period in three different areas were conducted, using a beach-seine net and three monofilament-gill nets with different mesh size. Twenty-eight species belonging to four bio-ecological categories were identified, five of them are new records for Mar Chiquita fish community. The correspondence analysis showed strong relationships between high salinity range and the abundance of Brevoortia aurea, Cynoscion guatucupa and Pomatomus saltatrix. Conversely, low salinity range corresponded to high abundance of Mugil platanus and Odontesthes argentinensis. High temperatures were corresponded with abundance of Micropogonias furnieri and Brevoortia aurea. In contrast, high abundance of both Odontesthes argentinensis and Oligosarcus jenynsii were corresponded to low temperatures. Brevoortia aurea, Mugil platanus and Odontesthes argentinensis were the most abundant species, representing more than 80% of the total capture. The group of estuarine-nondependent-marine fish presented the highest species richness. Estuarine-dependent-marine species presented for both juveniles and adults specimens the highest abundance values.

Little is known about the early development stages of Parablennius ruber. In this paper the following stages are described, and illustrations provided for the first time: middle stage egg, late stage egg, yolk-sac larva and preflexion larva. Recently laid eggs were spherical and orange, attached to the substratum in rock crevices. Eggs measured 1.02 mm in diameter. Newly hatched larva measured 4.65 mm total length and had the mouth closed and the anus open, fully pigmented eyes and a big yolk sac. Pectoral fins were present, rounded and not radially pigmented. Yolk was absorbed in 2–3 days at room temperature. Preflexion larvae had pointed pectoral fins, bigger eyes, well developed lips and strong jaws. Operculae were open. Orange chromatophores began to be noticeable between the eyes.

Reef fish community structures at three sites in the state of Rio de Janeiro (Pedra Vermelha (PV), Cabo Frio Island—Arraial do Cabo; Mãe Island (MI), Itaipu—Niterói; Comprida Island (CI), Cagarras Archipelago—Rio de Janeiro) were investigated to assess differences in fish species composition, density and distribution of trophic groups, between sites, correlating the observed patterns of fish distribution with environmental factors. Thirty-six visual strip-transects yielded 67 species of 34 families. Studied locations shared at least 40% of all species, mostly of western Atlantic distribution. The three sites presented significant differences on diversity, density and species dominance. CI presented the highest values, except for total density, which was higher at PV, probably due to its partial degree of protection. MI showed the lowest values, suggesting possible impacts from the proximity to the shore. The main trophic categories were omnivores followed by mobile invertebrate feeders, in similarity to what was previously observed for south-eastern Brazil. Inherent habitat features of each location regarding depth, declivity, visibility and rugosity resulted in different species distribution and dominance patterns.