The composition, taxonomic structure and distribution patterns of bathyal benthic fauna of the northern Mid-Atlantic Ridge between the Azores and the southern tip of the Reykjanes Ridge were studied from specimens collected on the ‘G.O. Sars MAR–ECO’ expedition in July 2004. Material was obtained from 16 Campelen 1800 trawls taken north of the Azores (42°N) and in two areas around the Charlie-Gibbs Fracture Zone (CGFZ) (51°N and 53°N) at depths 1237–3527 m. A total of 192 species were recorded. Overall the MAR–ECO benthic fauna was dominated by echinoderms (49.5% of the total species sampled), sponges (18.2%) and anthozoans (16.7%). Between-station species similarity was analysed using non-metric multidimensional scaling. Our analysis revealed differences between stations from the CGFZ and the Azorean regions. Stations from the Azores formed one cluster whereas stations from the CGFZ separated into two groups related to depth: stations from depths 1263 m to 1916 m and those from 2350 m to 3512 m. The taxonomic structure of the bathyal fauna was also different in the Azores than in the CGFZ areas. At the CGFZ, taxa with the highest percentage of species present were different above and below the 2000 m bathymetric contour, in contrast close to the Azores taxa with the highest percentage of species were the same shallower and deeper than 2000 m. Our results point at turnover in benthic bathyal fauna between the Charlie-Gibbs Fracture Zone and the Azores, which could be related to the presence of the Sub-Polar Front.

The interest in the knowledge of the ecology of soft-sediment communities is increasing due to the importance that these environments pose to ecologists and environmentalists. However, the ecology of Argentinean sandy beaches is almost unknown, in spite of being relatively common landscapes. In this work we describe and compare the macroinfaunal assemblages in the two largest sandy beaches within the Monte León National Park, the first marine-coastal park of Argentina. Macrobenthic samples were collected and environmental descriptions were performed by quantifying and comparing the organic matter content, grain size distribution and depth of the substratum available for macroinfaunal colonization. Results show that polychaetes and crustaceans are the dominant taxa and that the two beaches differ in the physicochemical characteristics, suggesting that a relation between the benthic fauna and physicochemical factors exists. Although they appeared similar at the landscape scale in preliminary visual surveys, the geomorphological differences between habitats are likely to drive strong differences in the structure of the macroinfaunal assemblages. The monitoring of visible landscape features is likely to undermine the efficiency of protection and managing strategies if not complemented by geomorphological and ecological surveys of less visible ecosystem variables.

During a survey of the marine meiobenthos in a predominantly muddy area, 40 km south of Venice (northern Adriatic Sea, Italy), 11 species of gastrotrichs were recorded. Gastrotrichs were found in 11 out of the 16 investigated stations, with densities (mean ± standard deviation) ranging from 0.6 ± 0.5 to 97.7 ± 71.2 ind./10 cm2. The community was dominated by Musellifer profundus, which made up 24.5% of the entire gastrotrich assemblage and reached in a single station the abundance peak of 18.3 ind./10 cm2. The finding bears relevance to the biogeography and ecology of several species. The presence of numerous specimens of the rare M. profundus allowed new insights into the arrangement and functioning of the hermaphroditic sexual apparatus in this phylogenetically important genus, for which such data are scanty. The new information will certainly be useful in evolutionary studies aimed at reconstructing the phylogenetic relationships within Gastrotricha, while offering at the same time additional morphological traits to be used in reliable species identification. Although only three species of Musellifer have been described so far, there are several others awaiting a formal affiliation, a task that will benefit from this new information.

The occurrence of most species is linked to the distribution of specific combinations of environmental variables that define their occupied niche. As a result, the relationship between environmental variables and species occurrence can be used to model species distribution. However, when collecting data to construct such models, it is preferable to ensure that the survey coverage is representative of all available habitat combinations within the area as a whole to ensure that the model does not under- or over-estimate the actual species distribution. By using multi-variate statistical techniques, a habitat representativeness score (HRS) can be calculated to provide an objective assessment of whether a specific survey coverage will collect (or has collected) data that are representative of all available habitat variable combinations in an area. To demonstrate this approach, HRSs calculated using principal component analysis were used to assess the minimum number of evenly-spaced parallel north–south surveys required to adequately survey two study areas with differing levels of environmental heterogeneity for all available combinations of four habitat variables. For the more environmentally homogeneous study area, the HRS suggests that for this survey design a minimum of five evenly-spaced parallel transects, covering around 5% of the study area, would be required to obtain representative survey coverage for these four variables. However, for the more heterogeneous study area, at least eight evenly-spaced parallel transects, covering around 9% of the study area, would be required. Therefore, for a given survey design, more survey effort is required to obtain a representative survey coverage when the survey area is more variable. In both cases, conducting fewer surveys than these minimum values would produce an unrepresentative data set and this could potentially lead to the production of species distribution models that do not accurately reflect the true species distribution.

Some sea cucumbers species are heavily exploited as bêche-de-mer for the Asian food industry and the global decline of certain highly sought after species has generated an interest in determining the ecological function of those animals within their ecosystem. This study investigated the ecological role of Holothuria scabra, a commercially valuable tropical species closely associated with seagrass beds. Seagrass productivity, seagrass and benthic microalgae (BMA) biomass and organic matter (OM) were measured during two exclusion experiments conducted using in situ cages deployed for two months both in 2003 and 2004. Density of H. scabra was manipulated in caged exclusions (near-zero density, ‘EX’), caged controls (natural densities, ‘CC’) and uncaged controls (natural density, ‘NC’). Seagrass growth was lower when holothurians were excluded (5% in 2003, 12% in 2004). Seagrass biomass decreased in all treatments, but reduction was greater in EX than in controls (18% in 2003, 21% in 2004). Both BMA biomass and OM increased in EX compared to NC/CC (in 2004). From a multivariate perspective, a principal component biplot separated EX from both types of controls in 2004, and multivariate tests based on four attributes supported this separation. These results indicate that seagrass systems may suffer in the absence of holothurians; however, the effect size varied between the two experiments, possibly because experiments were conducted at different times of the year. Nevertheless, our results suggest that holothurian over-fishing could have a negative impact on the productivity of seagrass systems.

It is widely assumed that optimal timing of larval release is of major importance to offspring survival, but the extent to which environmental factors entrain synchronous reproductive rhythms in natural populations is not well known. We sampled the broods of ovigerous females of the common shore crab Pachygrapsus transversus at both sheltered and exposed rocky shores interspersed along a 50-km coastline, during four different periods, to better assess inter-population differences of larval release timing and to test for the effect of wave action. Shore-specific patterns were consistent through time. Maximum release fell within 1 day around syzygies on all shores, which matched dates of maximum tidal amplitude. Within this very narrow range, populations at exposed shores anticipated hatching compared to those at sheltered areas, possibly due to mechanical stimulation by wave action. Average departures from syzygial release ranged consistently among shores from 2.4 to 3.3 days, but in this case we found no evidence for the effect of wave exposure. Therefore, processes varying at the scale of a few kilometres affect the precision of semilunar timing and may produce differences in the survival of recently hatched larvae. Understanding the underlying mechanisms causing departures from presumed optimal release timing is thus important for a more comprehensive evaluation of reproductive success of invertebrate populations.

Karyotypes for several East Pacific Rise hydrothermal vent invertebrates are described here for the first time: the vestimentiferans Riftia pachyptila and Oasisia alvinae, the alvinellid polychaetes Alvinella pompejana, A. caudata and Paralvinella grasslei, the polynoid polychaetes Branchinotogluma grasslei and Branchipolynoe symmytilida, the serpulid Laminatubus alvini and the mytilid bivalve Bathymodiolus thermophilus. For comparative purposes, the karyotype of the Atlantic vent mussel Bathymodiolus azoricus is also described here for the first time. Each species has its own unique chromosomal characteristics which can be interpreted both in terms of group characteristics and species divergence. From comparisons with published results on other vent species and closely-related coastal species, we identified a positive correlation between chromosome number variation and molecular divergence at two ribosomal ribonucleic acid gene loci (the 18S and 28S rRNA). Whilst the patterns of chromosome divergence we found were generally within the ranges previously reported for these taxonomic groupings, there was an apparent inconsistency in the case of Branchipolynoe symmytilida (EPR) and Branchipolynoe seepensis (MAR), which show a greater degree of divergence at the chromosome level compared with other members of the same genus. Moreover, polychaetes as a whole showed greater variation in the number and structural divergence of chromosomes compared to Mytilids (structural information only). Our findings highlight the great potential for chromosome analysis in future taxonomic and evolutionary studies of the deep-sea vent fauna.

The temporal and spatial variability in population dynamics of the European crab Carcinus maenas (L.) was studied between June 2003 and September 2007 in the Mondego estuary. An extreme climate event (extreme drought) occurred in 2004 and 2005 with a low freshwater flow discharge into the estuary, leading to an increase in salinity. Juveniles' recruitment was continuous throughout each year with a high proportion of young recruits being recorded in the spring of 2005. The proportion of green crabs clearly increased from the mouth to the upstream areas and the proportion of crabs actually in moult followed the same pattern. Parasitization by the endoparasitic barnacle, Sacculina carcini was observed, principally at the mouth of the estuary. The C. maenas population showed a regular size–frequency distribution and structure for both sexes during the study. Secondary production (P) of C. maenas estimated for the 4-year study period was different between years though, P/B ratios were similar during the whole study period. During the drought period, catches of the crab recruits were higher, particularly in the spring, probably due to the increase in salinity, which emphasizes the importance of these extreme events in controlling the abundances of coastal populations.

Seasonal and spatial variations in the composition and relative contribution of the harpacticoid species in the Mondego estuary (western Portugal) were studied based on a monthly sampling along a salinity gradient. These benthic harpacticoids were collected in the water column by means of a 63-µm plankton net. The influence of hydrological parameters (temperature, salinity, oxygen dissolved concentration, pH, turbidity, chlorophyll-a, total suspended solids and nutrient concentrations) was analysed by means of a redundancy data analysis. In addition, this is the first study to provide a checklist of benthic harpacticoids from this estuary. In total, 13 species plus six species not yet identified but known to belong to the genus Canuella, Microsetella, Ectinosoma, Mesochra, Harpacticus and Parapseudoleptomesochra were identified. Copepodites and adults of Euterpina acutifrons and Paronychocamptus nanus were most abundant in this harpacticoid community. While P. nanus dominated in winter and spring at upstream stations, E. acutifrons dominated more downstream. Although this species occurred along the whole salinity gradient, its highest abundances were found in the north arm of the estuary, except in autumn. This distribution may be due to the adaptability of E. acutifrons to different environments and the intermediate position between marine and estuarine conditions assigned to this species. Paraleptastacus cfr. spinicauda showed a relative occurrence of 5–10% in all stations, except at the mouth of the estuary (M). Tachidius discipes was found in low densities in Mondego estuary in spite of the large numbers of copepodites of this species in the southern arm, characterized by a high level of total suspended solids. The northern arm of the estuary was characterized by a higher numerical occurrence of harpacticoid organisms throughout the study years, with the higher densities towards the freshwater part (upstream areas). Canuella sp., Ectinosoma sp. (copepodite), Ectinosoma melaniceps, Leptocaris brevicornis, Phyllognathopus viguieri, Microsetella norvegica (copepodite) and Macrosetella gracilis (copepodite) were considered rare species. Nonetheless harpacticoid species were represented by a higher number of adults in the northern arm, and juveniles in the southern arm.

Every year, an undetermined number of loggerhead turtles cross the Gibraltar Strait entering and going out of the Mediterranean Sea. An unknown percentage of them strand on the Andalusian beaches, alive or dead, with an unequal distribution along the coast. We found a geographical pattern in the density of strandings, as well as in the proportion of them that were alive and dead. Atlantic areas receive a higher number of strandings, although most of them correspond to dead individuals, especially on the west coast (province of Huelva), whereas on the Mediterranean coast there is less difference between the number of alive and dead turtles stranded. The causes of stranding also presented a spatial segregation along these coasts: net fisheries were concentrated in Huelva, cold stunning was more frequent in Atlantic Cádiz, and debilitated turtle syndrome and longline were biased to the Mediterranean coast. The Atlantic areas might be an important accumulation zone for turtles, but where they endure a high human-induced stress and mortality. In the Mediterranean area, different causes, such as the narrowness of the Alborán basin, the ocean currents, human activity, or the number of turtles crossing, may increase the number of turtles stranding alive on the coast.

Four individuals of the large scyphozoan jellyfish Stygiomedusa gigantea were observed in the northern Gulf of Mexico over 2005–2009 by industrial remotely operated vehicles as part of the SERPENT Project. One of these observations included the symbiotic bythitid fish Thalassobathia pelagica. Prior to these observations, neither S. gigantea nor T. pelagica had been observed in, or collected from the Gulf of Mexico. In order to summarize the available information on S. gigantea, we located 110 observations obtained over 110 years (1899–2009) representing 118 individual specimens of this species from around the world. The resulting dataset confirms that this species is cosmopolitan occurring with records from all oceans except the Arctic. While the depth-range of the four Gulf of Mexico specimens was bathypelagic, there appears to be a pattern of S. gigantea occurring in mesopelagic and epipelagic depth-zones at high latitudes, particularly in the Southern Ocean and mesopelagic and bathypelagic depths at mid- and low-latitudes. This pattern may be related to the meridional vertical distribution of temperature or perhaps avoidance of light levels that could degrade porphyrin pigments. There was no evidence that this species migrates vertically. Two of the individuals in the Gulf of Mexico appeared to be actively clinging to subsea structures and we speculate that this is a consequence of its normal mode of feeding, which may entail using its large oral lobes to hold on to, and trap prey.

The recruitment of subtidal macrofouling organisms was studied in the Patagonian harbour of Comodoro Rivadavia (Argentina, 45°51′35″S 67°27′23″W). Changes in coverage and density were analysed in the central 100 cm2 of upper and lower surfaces which were replaced monthly from January to December 2004. The fouling assemblage consisted of algae, spirorbid polychaetes, compound ascidians, hydrozoans, bryozoans and egg masses spawned by the small fish Helcogrammoides cunninghami. Monthly changes in richness and diversity of taxa on upper and lower surfaces were significantly correlated with sea surface temperature. Fouling assemblage structure differed significantly between upper and lower surfaces. Filamentous algae were dominant on upper surfaces, while filter-feeding invertebrates were more abundant on the lower surfaces of the experimental panels. The density of the spirorbid Romanchella scoresbyi was two orders of magnitude higher on lower than on upper surfaces. Its recruitment began in late winter, reaching maximum values in spring.

Much is unknown about humpback whale (Megaptera novaeangliae) song. The behaviour is limited almost exclusively to males, occurs almost exclusively on the calving grounds and is identical within a population, although it changes periodically throughout the season. Much of current thinking associates humpback whale song with breeding, although it is not clear if it is intended to attract a mate, fend off challengers, or a combination of the two. There is, however, very little information on the internal biology of these large, sea-going mammals, so the majority of hypotheses have not considered much in the way of physiological mechanisms. Nonetheless, we believe that there is enough information available to infer that a seasonal process of neurological development and atrophy similar to that found in other animals may be present in humpback whales. We believe this explains why humpback whale song is not produced between breeding seasons and also why it does not vary between seasons, while it does so within a season. It also adds additional weight to the idea that humpback whale song is an honest signal of fitness to a potential mate or competitor.

The occurrence of pinnotherid crab Arcotheres tivelae in the bivalve mollusc Amiantis umbonella was investigated for one year on the Bandar Abbas coast (Persian Gulf, Iran). Specimens of A. umbonella were collected monthly from two transects from April 2007 to March 2008 and were investigated for presence of the Arcotheres tivelae. Infestation frequency of A. tivelae was 9.18% in a sample of 893 clams. From a total of 89 specimens of crabs, only eight were male. They were observed in late February and early March, all of them but one in association with female crabs. There was no significant difference between the sexes of the infested clams that pea crabs choose as a host. The mean carapace width of the crab A. tivelae was 7.7 ± 1.7 mm and the mean length of the Amiantis umbonella was 39.84 ± 8.93 mm. Clams in the mid and low tidal zones were more infested. There was no significant relationship between clam length–crab width (R2 = 0.28). The mean fecundity of crabs was 2517 ± 864 eggs. Infection caused a reduction of flesh weight of clams. There was no significant correlation between the frequency of crabs' occurrence and the temporal variability of water temperature, salinity, dissolved oxygen and pH in different months. This study provides the first report of the distribution of pea crabs A. tivelae in A. umbonella, a new clam host record in Iran.

The marine amphipod fauna of Tunisian shallow water was studied during 2003 to 2009. In this paper, we report—for the first time—the presence of two lessepsian amphipod species Elasmopus pectenicrus and Stenothoe gallensis from the south-east Tunisian coast.

Observations on gonad morphology and the structure of ovaries and testes of the coronate scyphozoans Atolla wyvillei and Periphylla periphylla are described based on samples collected from the Gulf of Mexico and Cape Hatteras (north-western Atlantic). In A. wyvillei, gonads of distinguishable sex were observed in medusae as small as 17 mm bell diameter (BD). Spermatogenesis occurred within follicles (average 366 × 254 μm) that were evenly distributed throughout the gonad. Oocytes in different stages of development were observed in all the females with gonads. Oocytes arise from the gastrodermis and migrate into the mesoglea to develop from early-mid to late vitellogenic oocytes characterized by a large nucleus and granular (organic-rich) cytoplasm. The largest oocytes measured were 543 μm and 263 μm from the Gulf of Mexico and Cape Hatteras respectively. Possible reasons for this difference are discussed. In P. periphylla gonads were also initially observed in medusae 17 mm BD, although not all larger medusae had obvious gonads. Unlike A. wyvillei sperm follicles were arranged in long convoluted rows normally only one follicle thick. The organization of ooytes in female P. periphylla was very similar to A. wyvillei, although the gonads were small and the number of oocytes present in each gonad very low (<22). The largest oocyte measured was 777 μm in a 53 mm BD medusa. Although medusae were collected from one time period only (September) in this study, our findings appear to be in agreement with literature evidence indicating that coronate jellyfish produce few eggs continuously over a long time period. Aspects of gonad development and gametogenesis are discussed with respect to potential differences in site productivity and species identification.

Size at morphological sexual maturity, sex-ratio, and the seasonal variation in abundance of the shrimp Artemesia longinaris Bate, 1888 were assessed off Pinheira Beach, Palhoça, Santa Catarina southern Brazil. Shrimp were collected monthly from November 2003 through to October 2004, in two areas that are customarily used by local traditional fishermen (27°52′–27°51′S and 48°33′–48°29′W). Of the total of 1099 specimens measured, 23.93% were males and 76.07% females. Mean size at first maturity (LM50) was estimated as 56.38 mm total length (TL) for males, and 70.34 mm TL for females. Females were significantly larger than males. Abundance of juveniles varied seasonally. A high predominance of juveniles in the areas sampled occurred in winter for both sexes, and in spring for females. In the summer and autumn, we observed a decrease in juveniles in both areas, mainly, area II. We suggest that the differential migration pattern of sexes during the reproductive cycle was the principal reason for the larger catch of females. The classical paradigm of continuous reproduction at lower latitude, with increased seasonality of the breeding period at higher latitudes, seems to apply to this species.

This study, carried out from August 2000 to July 2006, began out of the recognition of a special ecological situation, when an aggregation of juvenile green turtles (Chelonia mydas) was found inside the effluent discharge channel of a steel plant located near Vitória, the State of Espírito Santo capital, eastern Brazil. The green turtles were captured through either cast nets or a set net or by hand (one turtle was captured alive on one of the channel banks); after data collection, they were released back into the discharge channel. Information is here reported on the temporal pattern of occurrence, size-classes, residency, presence of tumours and growth rates of tumoured and non-tumoured green turtles in the study area. A total of 640 individual green turtles were captured in the six years; 448 of them were captured just once, and 192 were captured two or more times. Curved carapace length ranged between 25.2 and 77.5 cm. Among the captured green turtles, 59.1% were classified as being in normal body condition and without any tumours, 6.6% were either underweight or emaciated but without any tumours, and 34.4% had tumours, with different levels of the tumour severity score.