Samples were collected from 10 stations distributed through three sectors in Guanabara Bay during two consecutive years, in order to determine factors that influence the spatial pattern of molluscs and to describe the structure and composition of this community in a eutrophic estuarine system on the Brazilian coast. Although only one species, the gastropod Heleobia australis, comprised 77% of mollusc abundance, 59 species were identified in the bay. In addition to H. australis, three other species were dominant: the gastropod Anachis isabellei and the bivalves Americuna besnardi and Ervilia concentrica. The mollusc communities were significantly influenced by the spatial gradient; the outermost sector has marine conditions, and the other sectors are typically estuarine, leading to differences in the composition and abundance of molluscs. The outermost sector showed the highest diversity, which gradually decreased towards the innermost sector where the dominance of a few opportunistic species is favoured by highly organic mud sediments. Sediment type was strongly correlated with mollusc occurrence in the bay. Guanabara Bay showed two indicator species: the bivalve E. concentrica of the outer sector, and the gastropod H. australis of the intermediate sector. Our results suggest that benthic molluscs in Guanabara Bay show characteristics related to levels of environmental impact. A monitoring programme based on this community is needed to evaluate the effects of human impacts on this community and to monitor changes in its biodiversity in Guanabara Bay.

Larval survival during planktonic dispersal is crucial to the connectivity among benthic populations. Although predation has been suggested as an important cause of larval mortality, this process has rarely been quantified in the field. We measured the abundance of various larval species in the water column in St George’s Bay, Nova Scotia, Canada, on 3 different occasions in summer (August 2008, July and August 2009), the period of high larval abundance in our region. We sampled four numerically dominant predators (scyphozoans: Cyanea capillata and Aurelia aurita; fishes: Gasterosteus aculeatus and Merluccius bilinearis) and lobster larvae near the water surface with a neuston net and other larval species in the water column (3 m depth) with a ring net. Larvae found in the gut contents of the predators included various species of gastropods, crustaceans and bivalves, and these were more abundant in the scyphozoans than the fishes. We attribute these differences to variation in predation method. For certain larval taxa, we found significant differences between the proportional abundance in the guts of C. capillata and in the water column, indicating prey selectivity. This study evaluates the potential impact of predation on larval survival and indicates that the presence of predators can cause changes in abundance and consequent taxonomic shifts in species dominance of larvae, influencing their successful subsequent recruitment to the benthos.

To determine potential surrogates of littoral macroinvertebrate communities for marine bioassessment and for evaluating biological conservation, the different taxonomic resolutions as surrogates were studied based on six datasets collected from intertidal zones of the Yellow Sea, near Qingdao, northern China, during the period of 1989–1998. Samples were collected yearly at five stations with different bottom types during the summer season (June). The genus- and family-level resolutions maintained sufficient information to analyse the ecological patterns of the macroinvertebrate communities for assessing ecological quality status in littoral ecosystems. The mollusc assemblages, alone or in combination with arthropod assemblages, may be used as a surrogate of littoral macroinvertebrate communities, at both species- and genus-level resolutions. The results suggest that the use of simplifications in macroinvertebrate fauna at genus-level resolutions or using smaller taxonomic assemblages (e.g. molluscs and arthropods) are time-efficient and would allow improving sampling strategies of large spatial/temporal scale bioassessment programmes and biological conservation researches in littoral ecosystems.

The analysis of changes in benthic community structure using multivariate techniques has been successfully applied to the detection and monitoring of impacts caused by oil related activities. A survey to assess the status of the benthos was performed prior to a scheduled exploratory drilling at Banco Sarmiento, a shoal located off the eastern mouth of the Strait of Magellan (south-west Atlantic). The aims of this study are to provide baseline data about the composition and structure of the subtidal macrobenthic assemblages, to analyse the relationships between biodiversity and environmental variables, and to compare its benthic assemblages with those of neighbouring areas. Multivariate analyses classified the stations in two major groups, one composed of relatively shallow stations with coarse sediments dominated by filter-feeders, and the other consisting of stations with a high proportion of sand and mud dominated by deposit-feeders. Poorly sorted sediments had higher species richness than well sorted sediments. Shallow stations showed the lowest taxonomic distinctness due to the occurrence of a high proportion of bryozoans encrusting hard substrata. A five-fold increase in biodiversity can occur at scales of tens of km, suggesting that generalizations on regional biodiversity patterns should be made with caution because of the different gears used during the collection of samples, and should be based on a thorough knowledge about the physical environment.

The distribution and composition of molluscan assemblages of seagrass beds in the Ensenada de O Grove (north-western Spain), are described in this paper. The studied bottoms were mostly muddy and colonized predominantly by Zostera marina L., Z. noltei Hornemann, or by both species. Molluscan fauna was dominated by gastropods and bivalves, in terms of both species richness and abundance. A total of 7641 individuals belonging to 68 taxa was identified. The most abundant species were the gastropods Peringia ulvae, Retusa truncatula and Calyptraea chinensis and the bivalves Abra alba, Loripes lucinalis and Kurtiella bidentata. Cluster and multidimensional scaling analyses based on Bray–Curtis similarity coefficient showed two distinct faunal assemblages. Group A comprised intertidal sites colonized either by Z. noltei or by Z. marina and Z. noltei on muddy sand and sandy mud bottoms and subtidal sites exclusively colonized by Z. marina in the outer part of the inlet on muddy sand with the highest values of species richness and diversity. Group B consisted of sites characterized by low values of species diversity and a species composition typical of a ‘reduced Macoma community’. The sorting coefficient and the combination of gravel, sorting coefficient and carbonates content (BIOENV analyses) and the salinity of bottom water and depth (canonical correspondence analyses) were the most important abiotic variables in explaining the structure of the molluscan assemblage.

Nectonema species are parasites of decapod crustaceans and the only known representatives of the otherwise freshwater/terrestrial taxon Nematomorpha. We report the American lobster, Homarus americanus, as a new host for Nectonema agile, a first record among astacidean decapods. A female, about 590 mm long, was found in the body cavity of one female lobster specimen. We assume lobster to be a very rare host for Nectonema.

The digestive system of sea spiders (Pycnogonida) presents peculiarities that have not been discussed in the context of their ecology or feeding behaviour. We investigated the digestive system of two Mediterranean species, a carnivorous species Ammothella longipes and a detritivorous Endeis spinosa, with special focus on its correlation with behavioural feeding habits. The midgut and hindgut sections did not present significant differences between the two species, but major differences were observed in the foregut, reflecting concordance to their diet and their feeding behaviour. Jaws, setose lips, the structure of the pharyngeal filter and musculature of the proboscis are the main differential elements when comparing feeding habits of A. longipes and E. spinosa. These elements are responsible for the reduction of the food pulp down to subcellular size. The digestion process observed in the species studied agrees with that observed in other pycnogonid lineages, but differs from most marine arthropods mainly because of the absence of midgut gland cells and the presence of a unique multifunctional type of midgut epithelial cell. Epithelial digestive cells are present in a small ‘resting’ form during starvation periods. During digestion, secretion granules possibly containing zymogen move to their apical border to be secreted to the midgut lumen, secondary lysosomes are formed and intracellular digestion occurs within them. Residual bodies are formed within the epithelial cell and released to the midgut lumen to be transported towards the hindgut. The characteristics of the digestive process of the pycnogonids studied seem to reflect a plesiomorphic state in arthropods.

Diel rhythms in feeding and spawning were investigated in Centropages tenuiremis from Xiamen Bay in March to May, 2006. Circular statistics were used to determine the peak time of spawning. The results showed that the feeding activities of females were stably higher at night-time, and there was a remarkable earlier shift in spawning peak time with warmer seawater. Thus, the lag times between peak times of gut pigment content and spawning were shortened with the increase of temperature. It suggested that there was a direct effect of feeding rhythms on egg production variations in copepods, and the seawater temperature would work on the converting time and then influence the spawning peak time. So the effect of temperature cannot be ignored in the investigation of the effects of feeding on egg production.

Mesophotic coral ecosystems (MCEs) are found on the insular and continental slopes of Caribbean islands and comprise mainly scleractinian corals, sponges and macroalgae. These species provide habitat for a highly diverse and specialized crustacean fauna. A new genus and species of the family Louriniidae is described from samples taken from an MCE in south-west Puerto Rico. The new taxa can be diagnosed by: body elongate, almost cylindrical and with inconspicuous podoplean boundary between prosome and urosome; double genital somite with a discontinuous chitinized cuticular ridge; telson short with rectangular anal operculum; furca short; rostrum sinusoidal, well defined at the base; antennules 7-segmented with aesthetasc on the fourth segment; antenna with a brush-like basal seta and an abexopodal seta, exopod 1-segmented with 2 setae; endopod with 7 elements (1 geniculate seta and 1 modified inner spine); maxilliped well developed, prehensile, composed of syncoxa, basis, one segmented endopod and one claw-like apical seta; leg 1 endopod 3-segmented, first segment with a modified inner seta; legs 2, 3 and 4 with 2-segmented endopod with inner seta on the first segment; leg 5 basendopod fused, well developed with 4 setae, exopod well developed, with 5 setae; leg 6 represented by a single seta; and genital slits wide apart. The new genus and species can be confidently assigned to the family Louriniidae on the basis of the following synapomorphies: rostrum well-developed with rounded tip; antennule of female 7-segmented; mandible palp reduced; maxillule endopod and exopod absent; maxillae endopodite 2 represented by 3 setae; leg 5 basoendopod of female confluent, intercoxal sclerite absent, exopod 1-segmented; eggs retained in a single ventral egg sac; telson shorter than last urosomite; and furca short and with 6 setae.

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.

This investigation aimed to study the relative growth, morphological sexual maturity and fecundity of the swimming crab Achelous spinicarpus in a tropical region, on the south-eastern continental shelf of Brazil (25°S). Biometry of all specimens was conducted, including measurements of the cephalothorax, cheliped, abdomen and gonopods. Relative growth was described based on the equation for allometry (y = axb), and size at sexual maturity was determined from inflections in relations involving the cheliped, gonopods (males), and abdomen (females), as dependent variables, related to the cephalothorax width (independent variable). Fecundity was estimated by the gravimetric method. The relations of the length of the chelar propodus and carpal spine to the carapace width without the lateral spines (CW) showed positive allometry in both sexes, with a significant variation in the constant ‘b’ for males between the developmental stages (juvenile and adult) and the size at maturity estimated at 37 mm CW. In females, the abdomen was most appropriate for the estimate of morphological maturity, which occurred at a smaller size (32 mm CW), with a change in the growth pattern between the stages, passing from isometric (juveniles) to positive allometric (adults). The gonopods also showed different growth rates between developmental stages, in synchrony with the variables of the cheliped. Mean fecundity for the species was 53,984 eggs, with a positive correlation between the number of eggs exteriorized and the size of the female; the equations allowed interconversion between these variables, due to the adjustment of the power function (r2 ≥ 86%).

The aim of this paper is to describe the population structure and some reproductive aspects of Hippolyte zostericola during an annual cycle. Samples were taken bimonthly, from June 2009 to April 2010, with a Colman–Seagrove sledge net on seagrass meadows located in the internal margin of Isla del Carmen, Campeche, Mexico. The population structure of H. zostericola was similar throughout the cycle analysed. The males, significantly smaller than females (0.57–1.8 and 0.55–3.52 mm carapace length (CL), respectively), were more frequent between 0.8 and 1.54 mm CL, whereas in larger size-classes (1.8–3.52 mm CL) only females were registered, ovigerous principally. The sex-ratio was always in favour of males, mean of 1.3 males per female. Size at maturity (CL50) was 2.28 ± 0.1 mm CL. Based on the presence of ovigerous females throughout the year it is considered that the reproduction of H. zostericola is continuous. The main breeding season and recruitment occurs during the first third of the year. The mean fecundity of the species was 144 ± 69 eggs and varies with female size. The higher egg loss occurred in larger females (37.3%) and the relationship between fecundity and female size was estimated as negative allometric, which suggests that age influences the fecundity of the species.

The objective of this study was to analyse the differences in shape of the cephalothorax in four fishery stocks of sea-bob shrimp Xiphopenaeus kroyeri that are distributed on the east coast of Brazil, applying geometric morphometry as the analytical tool. Samples were collected at the fishing ports of Caravelas (17°43′S 39°15′W), Vitória (20°15′S 40°14′W), Atafona (21°35′S 41°01′W) and Farol de São Tomé (22°02′S 41°02′W), and variations in shape of the cephalothorax of the shrimps were evaluated by univariate and multivariate techniques. Analysis of variance followed by the Tukey test indicated that shrimps collected at the port of Farol de São Tomé were significantly smaller than the others, and size of individuals was inversely related to latitude. Discriminant analysis revealed the formation of two morphologically different groups between the areas of collection. Individuals collected in Caravelas, Vitória and Atafona, suffering permanent influence of freshwater discharge, associated with sandy–muddy substrate, constituted a different group compared to individuals collected in Farol de São Tomé, area without this kind of influence and with sandy substrate, where the average water temperature is lower and salinity is higher. Considering the commercial importance of the target species, the technique could be applied to its fisheries management. It allows the recognition of stocks and inference about the processes of fishing area occupation.

The population biology of Epialtus bituberculatus was compared between two different intertidal localities with differing levels of wave exposure. Sampling was conducted monthly between January and December, 2001 on seaweed banks of Sargassum cymosum in the intertidal zone of the rocky shores Grande (GR) (23°23′S–45°03′W) and Domingas Dias (DD) (23°29′S–45°08′W). Four hundred and twenty-eight crabs were captured at the GR site: 111 juvenile males, 106 adult males, 57 juvenile females, 17 adult females and 137 ovigerous females; while 455 specimens were obtained at the DD site: 76 juvenile males, 113 adult males, 37 juvenile females, 40 adult females and 189 ovigerous females. The population from GR showed a non-normal distribution and from DD a normal distribution. The sex-ratio (female/male) was 1:0.97 at GR (χ2 = 0.77, P = 0.084), whereas it was 1:1.41 at DD (χ2 = 13.03, P < 0.001). The largest individuals occurred at DD (U = 78249.0, P < 0.001). The estimated size at sexual maturity was 6.3 and 5.0 mm carapace width (CW) for males, and 5.4 and 5.2 mm CW for females, from GR and DD, respectively. The observed differences in E. bituberculatus between the studied localities might be explained by the different degrees of wave exposure between sites. However, other factors that might also explain the observed differences (e.g. temperature, salinity and food availability) cannot be discarded as relevant in influencing the population structure between sites herein studied.

The land crab, Discoplax celeste (Gecarcinidae) is endemic to Christmas Island in the Indian Ocean. Due to a freshwater-dependant life history, in which the megalopae migrate from the ocean up freshwater streams to their adult terrestrial/freshwater habitat, D. celeste inhabits only a few isolated locations on the island. This restricted distribution is one of a number of factors which has previously highlighted the vulnerability of this species to outside threats. A number of anthropogenic factors including the introduction of multiple invasive species and habitat destruction have led to drastic ecosystem change on Christmas Island. The aim of this study was to investigate whether the restricted geographical distributions of D. celeste populations contribute to significant genetic structuring across Christmas Island, with an objective to inform future conservation strategies for this species on Christmas Island. Fragments of the mitochondrial cytochrome oxidase I gene and the control region were sequenced from 95 individuals collected from all five locations on Christmas Island known to be inhabited by D. celeste. Analyses using analysis of molecular variance revealed no evidence of population sub-structuring, indicating that despite any geographical isolation, there is a single population of D. celeste on Christmas Island. This lack of population differentiation is probably explained by the oceanic dispersal of larvae, rather than terrestrial migration of D. celeste. Therefore, based on these results, for conservation purposes, D. celeste on Christmas Island can be considered a single management unit.

Austinixa aidae inhabits burrows of the ghost shrimp Callichirus major at Perequê-açu beach, Ubatuba, Brazil. We described the host-use pattern and sexual dimorphism of A. aidae to test for monogamy given the generality of this mating system in the subfamily Pinnothereliinae (family Pinnotheridae) to which A. aidae belongs. Against expectations, A. aidae lives as solitary individuals within burrows more frequently than expected by chance alone. Additional observations suggested that A. aidae exhibits a polygynandrous mating system with males moving among burrows in search of receptive females. First, only 21% of the burrows harboured heterosexual pairs of crabs and the body size of paired crabs was poorly correlated. This suggests pair instability and frequent shifts among burrows by male and/or female crabs, as reported before for other symbiotic crustaceans in which the body size of paired crabs is poorly correlated. Second, males paired with females that were sexually receptive (without embryos) or that have been receptive recently (carrying early embryos) were found more frequently than expected by chance alone. The above agrees with that reported for species in which sexual pairing does not last long. Third, sexual dimorphism in terms of claw size and coloration was evident. Claws were larger in males than in females, a condition that argues in favour of male–male competition in A. aidae. In addition, the body coloration of males was more similar to the sand grains of the beach than that of females. This sex-specific coloration suggests that males are ‘better adapted' than females to roam on the surface of the beach in search of burrows because their coloration should diminish the risk of detection by predators. Experiments are needed to reveal the details of the polygynandrous mating system herein inferred for A. aidae and to understand those conditions favouring particular reproductive strategies in symbiotic decapod crustaceans.

The decorator crab, Microphrys bicornutus, is a common inhabitant of the turtle grass Thalassia testudinum. In order to establish the behaviour of a population of this species in an extreme shallow Thalassia complex (maximum depth less than 50 cm, and often exposed to the air), size distribution, population dynamics, reproductive effort and egg size were studied in Buchuaco—Venezuela. Monthly sampling was undertaken between June 1988 and December 1990. A total of 1403 specimens of M. bicornutus were captured. In each of the sampled years, size distribution was strongly skewed to the predominance of small size crabs. Females were significantly larger than males in all the three years. Small size and large size crabs showed periodic annual fluctuations in abundance, with peaks during the last months of the year for the first, and peaks between April and June for the latter. Medium size crabs showed no periodicity at all. Number of eggs per female ranged between 40 and 4305 (mean = 1067.4), and was positively correlated with female body size. Eggs increased their size gradually during their development, and differences in egg size between development stages were significant. The biological parameters found in this study are compared with other populations of this crab, found in Venezuela and Brazil, in different ecosystems. Results acquired in this work add new insights to the behaviour of this decorator crab, specifically on density variation and egg size (among others), living in an environment that is constantly exposed to air and to other physicochemical variations.

The present study investigated the reproductive biology of the pink shrimp Farfantepenaeus brasiliensis and Farfantepenaeus paulensis captured offshore and at two important fishing grounds, Guanabara Bay and Araruama Lagoon both on the south-eastern Brazil coast. The females’ size at first maturation was 37.90 mm of carapace length (CL) for F. brasiliensis and 41.95 mm of CL for F. paulensis. Both species presented continuous reproduction with two spawning peaks. For F. brasiliensis these peaks occurred during summer and winter and for F. paulensis during summer and autumn. The sex-ratio of the pink shrimp was favourable to the number of females which can be a strategy to guarantee the reproduction.

A new species of the hippolytid shrimp genus Lebbeus White, 1847 is described from the Von Damm Vent Field (VDVF) on the Mid-Cayman Spreading Centre, Caribbean Sea, at 2294 m water depth. Lebbeus virentova sp. nov. is defined and illustrated from seven specimens, with brief notes on its distribution and habitat. Molecular phylogenetic data from the COI mDNA region are used to analyse the species’ phylogenetic position, and its morphology is compared with previously described species. This new species represents the second family of caridean shrimp to be reported from the VDVF. Lebbeus virentova sp. nov. is the eighth member of the genus to be described from hydrothermal vents and appears to be the first hippolytid shrimp at a vent field known from outside the Pacific Ocean.

The abundance and ecological distribution of Acetes americanus and Peisos petrunkevitchi were investigated from July 2006 to June 2007, in Ubatuba, Brazil. Eight transects were identified and sampled monthly: six of these transects were located in Ubatuba bay, with depths reaching 21 m, and the other two transects were in estuarine environments. A total of 33,888 A. americanus shrimp were captured, with the majority coming from the shallower transects (up to 10 m). Conversely, 6,173 of the P. petrunkevitchi shrimps were captured in deeper areas (from 9 to 21 m). No individuals from either species were found in the estuary. The highest abundances obtained for both species were sampled during the summer. Canonical correlation analysis resulted in a coefficient value of 0.68 (P = 0.00). The abundance of both species was strongly correlated with depth. Variations in temperature and salinity values were also informative in predicting the seasonal presence of P. petrunkevitchi in deeper areas and A. americanus in the shallower areas of the bay. It is conceivable that the shrimp adjust their ecological distribution according to their intrinsic physiological limitations.