We investigated the occurrence and seasonal variation of the biomass of rotifers, tintinnids, the heterotrophic dinoflagellate Gyrodinium fusus and copepod nauplii in the Bahía Blanca Estuary (38°42′S61°50 ′W), Argentina, during an annual cycle. The rotifers fauna comprised three species, while the tintinnids were represented by sixteen species. The biomass of the rotifers fluctuated between 0.62 and 8.90 µgC l−1. The biomass of the tintinnids fluctuated between 0.13 and 9.37 µgC l−1, the biomass of the nauplii stages between 1.78 and 7.65 µgC l−1; while the biomass of G. fusus varied from 0.26 and 7.94 µgC l−1, these results are compared to estimates of microzooplankton in other regions. We analysed the presence of the different groups in relation to the environmental variables, based on point-biserial correlation. Salinity fluctuated between 25.14 and 36.64; temperature between 7.5 and 23.2°C, solar radiation between 0.9 and 30.8 MJ m−2d−1 and Secchi distance between 0.25 and 1.43 m. Rotifers were correlated positively with temperature, chlorophyll-a and Secchi depth and negatively with salinity. The tintinnids were positively correlated with salinity. Gyrodinium fusus was positively correlated with Secchi depth, and chlorophyll-a, and negatively with temperature and solar radiation. Nauplii stages were negatively correlated with chlorophyll-a. Based on the occurrence of the microzooplankters in relation to the physico-chemical variables, it was possible to establish two seasonal assemblages: (a) the co-occurrence of the rotifers and the heterotrophic dinoflagellate G. fusus during the winter–spring; and (b) the tintinnids and nauplii larvae during the summer. We conclude that, in this estuary, physico-chemical variables are the forcing factors that directly, or indirectly, influence the seasonal assemblages of the microzooplankton.

Sedentary consumers play an important role on populations of prey and, hence, their patterns of abundance, distribution and coexistence on shores are important to evaluate their potential influence on ecosystem dynamics. Here, we aimed to describe their spatio-temporal distribution and abundance in relation to wave exposure in the intertidal rocky shores of the south-west Atlantic to provide a basis for further understanding of ecological processes in this system. The abundance and composition of the functional groups of sessile organisms and sedentary consumers were taken by sampling the intertidal of sheltered and moderately exposed shores during a period of one year. The sublittoral fringe of sheltered areas was dominated by macroalgae, while the low midlittoral was dominated by bare rock and barnacles. In contrast, filter-feeding animals prevailed at exposed shores, probably explaining the higher abundance of the predator Stramonita haemastoma at these locations. Limpets were more abundant at the midlittoral zone of all shores while sea urchins were exclusively found at the sublittoral fringe of moderately exposed shores, therefore, adding grazing pressure on these areas. The results showed patterns of coexistence, distribution and abundance of those organisms in this subtropical area, presumably as a result of wave action, competition and prey availability. It also brought insights on the influence of top-down and bottom-up processes in this area.

The construction of an artificial channel to a small embayment in the Chetumal Bay coastal lagoon complex, located on the Caribbean coast of Mexico, provided an opportunity to evaluate how large environmental changes influenced the structure of a low diversity benthic system. The objective of this study was to demonstrate that despite the absence of previous baseline information, the artificial channel has induced measurable changes in the biodiversity patterns of a hard substrata benthic community. The experimental design took into account the environmental setting influencing local benthic community structure and the sources of variability as a result of different substrate types and water depth. Four localities with ten replicates each were surveyed, and the presence/absence of macrobenthic biota species recorded during the rainy season. Our analysis using permutational multivariate analysis of variance indicated a significant increase in species richness in locations adjacent to the artificial channel. The highest species richness (66 species) was observed in the immediate area adjacent to the artificial channel and where exclusive species density was three to six times (18 exclusive species) than those present in other localities (6, 5 and 3 species) away from the channel. The presence of six species of hard corals indicated that the artificial channel offers a more suitable habitat for marine organisms colonizing the area than the natural channel. This study indicates the relative significance of confinement in structuring coastal lagoon benthic assemblages in tropical systems. Our results are similar to other findings underscoring the rate of colonization of marine organisms as a relevant process to explain benthic assemblage gradients and the importance of spatial–temporal interactions. The changes in species diversity caused by the artificial channel were clearly identified based on a sampling design that incorporated the main sources of environmental variability (distance to channels, substrate type and depth). Our study further demonstrates that changes in benthic community structure in the Chetumal Bay lagoon complex, as a result of human impacts, can be assessed even when community structure data before impact are absent.

This study describes species of the genus Hymedesmia from three areas of cold-water coral reef: Mingulay Reef Complex (Scotland, UK) and Rockall and Porcupine Banks (off UK and Irish coasts). Five new species are described: Hymedesmia (Hymedesmia) gibbosa, H. stoneae, H. tendali, H. xavierae and H. valentinae. Records are provided of other poorly known Hymedesmia species: H. bocki, H. cohesibacilla, H. curvichela, H. ebria, H. gustafsoni, H. simillima, H. irregularis, H. proxima, H. hibernica and H. primitiva. Information on distribution of other Hymedesmia species occurring in Britain and Ireland is presented. The sites studied represent a variety of depth-ranges and the data collected suggest that some Hymedesmia species may be restricted to particular bathymetric zones.

Three new species of coral reef boring sponges were found in remote coral reefs from Revillagigedo Island, an archipelago that is 386 km from the continent. Cliona medinae sp. nov. is a sponge with orange-yellow papillae characterized by short almost straight spirasters. Cliona tropicalis sp. nov., is a yellow papillate sponge with a spicule complement similar to the species included in the Cliona viridis complex. However, the new species differs from the rest of the species mainly in its external morphology and by differences in the size and shape of spicules. Thoosa purpurea sp. nov. is characterized by its purple colour, and the spicular complement formed by tylostyles, two amphiaster categories, bi- tri- and tetra-radiate oxyasters and smooth or microspined centrotylote oxeas. In addition, Cliothosa tylostrongylata sp. nov. is also described from coral reefs from the southern Mexican Pacific Ocean. This is a light red species, with tylostyles and tylostrongyles as megascleres and ramose and nodulose amphiasters as microscleres. The four species were found exclusively excavating skeletons of live or dead corals of the genus Pocillopora. This study increases the number of boring sponges known from the Mexican Pacific Ocean to 22 species and it is the first study on marine sponge fauna from the Revillagigedo archipelago.

Phylogeography and population genetic studies in the Porifera have been limited by the lack of available polymorphic DNA markers. In this paper, we tested four new mitochondrial markers in nine demosponge species from a wide taxonomic range: partial sequences of the ATP synthase 6 (ATP6) and the cytochrome oxidase 2 (CO2) genes and two spacers: one located between ATP6 and CO2 and the other between the NADH dehydrogenase subunit 5 (ND5) and the small subunit ribosomal RNA (rns) genes. The new markers presented levels of nucleotide diversity up to 2.4 times higher (π = 0.015 for CO2) than those observed for the most commonly used mitochondrial marker in sponges, the cytochrome oxidase 1 gene (π = 0.006), making them suitable for alpha-level systematics, phylogeography and population genetics studies. 

Halicarcinus planatus is the only species of the genus occurring at the southern tip of South America, in sub-Antarctic, cold-temperate waters. Previously it has been shown that the population from the estuary of the Deseado River presents a spatial segregation by sex, a complete overlapping of sizes among adolescents and adult females. Females go through two reproductive seasons, separated by a resting period during late summer and early autumn, and 7 to 8 spawns are produced following a single mating. The aims of the present work were to evaluate the duration of the embryonic development until hatching during successive spawning, to determine the fecundity and to discuss the adaptive reproductive strategies of this population. Breeding occurs from nearly 2°C to above 16°C. The incubation period lasts nearly 100 days in winter and between 30 and 40 days in summer. The fecundity ranged from 210 to 2150 eggs, it differs between successive spawning and a positive relationship was found between fecundity and carapace width. This population has the highest fecundity compared to other populations, but also compared to other species of the genus. The high number of successive spawns is directly linked to the increase of seawater temperature by the end of spring and during summer. This way, this species would be very well adapted to live in the more temperate waters of Patagonian coasts.

The larval development of the hermit crab Areopaguristes nigroapiculus (Komai, 2009) (Decapoda: Anomura: Diogenidae) is described and illustrated from the material reared in the laboratory. The development included three zoeal and a single megalopal stages. At 22–25°C, megalop of A. nigroapiculus was attained 6–9 days after hatching. The present paper is the first description of the complete larval development in the genus Areopaguristes. Morphological characters of zoeas and megalop of A. nigroapiculus are compared with those described for the closely related Paguristes species. The comparison on the zoeal characters revealed that A. nigroapiculus is distinguished from Paguristes species by the absence of anterolateral carapace spines and by the fused fourth telson process in zoea III. These two features are possible generic characters of Areopaguristes. In the rest of larval characters, A. nigroapiculus agree well with Paguristes species having three zoeal stages. In the plankton of Peter the Great Bay, the larvae of A. nigroapiculus sporadically occurred only in July and August, at depths of 3–45 m and surface water temperatures of 18–22°C.

Many crustaceans with spatial segregation may present differential body coloration depending on the habitat they inhabit. Since crustaceans are unable to synthesize carotenoids, individuals must acquire them from their diet, so diet changes can modify individual coloration. The burrowing crab Neohelice (=Chasmagnathus) granulata inhabits the intertidal, from the uppermost parts of salt marshes to the lowest mudflat zones with a spatial segregation of different size-classes. They are primarily deposit feeders in mud flats and herbivorous–detritivorous in the salt marsh. We analysed the effect of intermoult length on the carapace colour of N. granulata, and the changes in carapace colour with crab size and zone. Crab colour varied between unvegetated and vegetated areas. Some of these differences were in part caused by colour changes related to crab size. Larger crabs show less intensive colours, and given that they inhabit the upper part of the intertidal a differential coloration pattern occurred between zones. In field experiments intermoult duration affected crab colour and some body regions analysed showed differences between zones unrelated to size.

Normal females of the mud shrimp, Upogebia major, have a pair of pleopods on the first abdominal segment, while normal males do not. We have investigated nine populations in the Seto-Inland Sea, Japan, and found morphological disorders on the first abdominal segments of both males and females. In males, the first pleopods occurred. Morphology and arrangement of these additional pleopods were classified into four types. The pleopods of Types M-1 and M-2 were similar in structure to those of normal females. These males could be considered as de-masculinized individuals, and the occurrence of males with these morphological disorders showed local variation: while their frequency was high in two specific sites in Kasaoka Inlet (11.5% in Site 6 and 5.5% in Site 7), it was less than 3.5% in other sites. Other types had abnormal additional appendages similar to the walking legs (pereiopods) (Type M-3) or biramous leaf-like pleopods (Type M-4), but their frequency was extremely low (only 3 out of 1558 males inspected). Morphological disorders in males (Types M-1 and M-2) occurred independently of gonadal development, and did not affect the sexual characteristics as revealed by analyses of allometric growth and gonadal index. In females, morphological disorders were classified into five types: incomplete first pleopods (Type F-1); lack of the first pleopods (Type F-2 and F-3); transformation into the pereiopod-like pleopods (Type F-4); and biramous leaf-like pleopods (Type F-5). The frequency of Types 1–3 was especially high in Site 6 in Kasaoka Inlet (24.4%), but was less than 9.4% in other sites. A feature was that cuticular lesions often co-occurred with the morphological disorders. Possible causal factors of these abnormalities are discussed.

One of the most problematic fishing methods in terms of by-catch and discarding is prawn-trawling. This paper analyses the incidental catch of an artisanal trawl fleet during two discrete Artemesia longinaris fishery seasons (2002 and 2004). The fishery season of A. longinaris operates monthly and it takes place in the surrounding area of the Barra do Rio Grande. Sampling was carried out during the fishing season (April–December) always on the same artisanal trawl boat. An observer was included on-board to avoid loss of information due to discards made by the fishermen at sea. Fifty species were caught: 38 fish and 12 crustaceans. Discrete fauna abundance and composition were recorded in analysed years, with higher by-catch ratios associated with elevated rainfall and low salinity. The overall discard ratio was 1:5.6, with values ranging from 1:11.3 in 2002 to 1:2.5 in 2004. The most striking differences between both years analysed were observed during autumn (1:75 in 2002 and 1:11.30 in 2004) and winter (1:16 in 2002 and 1:0.97 in 2004), while spring presented similar values (1:8 in 2002 and 1:4 in 2004). The discard ratio estimated in terms of number showed a different pattern, presenting overall values of 1:2.24 in 2002 and 1:0.5 in 2004. Higher estuarine runoff may have increased biomass production in the surrounding area of Patos Lagoon during 2002, sustaining higher abundance of estuarine-related and marine species in the area, as well as higher mean trophic level and abundance of top-predators. Conversely, A. longinaris production was consistently lower, since this marine species does not tolerate marked reductions in salinity. In 2004, salinity was higher, associated with low rainfall and favouring A. longinaris abundance in the area. During this dry year, the target-species was dominant in samples resulting in very low by-catch ratios, especially in winter (1:0.97). The catch was mainly composed of juvenile fish, since fishery is performed in nursery grounds.

The antifouling activity of a series of hexane, ethyl acetate, ethanol and aqueous extracts from 11 species of marine sessile organisms collected from the south-east coast of China was investigated. Settlement inhibition of cyprid larvae of the barnacle Balanus albicostatus was used to evaluate their antifouling efficacy. Screening of the 44 extracts showed antifouling activity in 90.9% of the hexane extracts followed by 90.9% of the ethyl acetate, 72.7% of the ethanol and 36.4% of the aqueous extracts. The hexane extracts of Tubularia mesembryanthemum, Notarcus leachii cirrosus and Styela canopus, the ethyl acetate extracts of Bugula neritina and N. leachii cirrosus, and the ethanol extracts of B. neritina and Anthopleura sp. were the most active in inhibiting the settlement of B. albicostatus, with EC50 values all below 50 μg/ml. At least one of the four extracts of each tested species exhibited antifouling activity, suggesting that all 11 marine sessile organisms contained antifouling substances and they may have evolved chemical defences against biofouling on their surfaces.

The present paper is the first scanning electron microscope (SEM) description of a protonymphon larva of an Ammotheidae. The morphology of the first larval instar of Achelia assimilis is described in detail and illustrated for the first time. The morphological characters are compared to previous larval descriptions of other pycnogonid species. The larvae are integrated into Bain's classification of larval types within the pycnogonids (Bain, 2003a) as a ‘typical protonymphon’. Larvae were obtained from ovigerous males, caught in Punta Huinay, Huinay, Chile and analysed with light microscope and SEM. Descriptions of pycnogonid protonymphons at a species-specific level in the future will contribute to a deeper understanding of larval pycnogonid taxonomy at the level of differential diagnoses.

Phenotypic variation on shell size and shape of Olivancillaria carcellesi from four representative localities is confirmed using geometric morphometric techniques. This species lives along the entire range of the genus in subtidal soft bottoms from Rio de Janeiro (Brazil) to Punta Pardelas (Chubut, Argentina). Thickness of columellar callus, length and width are the main shell differences from specimens collected at several intermediate localities: Cassino (Brazil), La Paloma (Uruguay) and Mar del Plata (Argentina). All forms showed significant differences in shell size except O. carcellesi from La Paloma compared with those from Mar del Plata. The group with larger specimens was from Cassino. Olivancillaria carcellesi from Punta Pardelas, the southernmost population, was the smaller sized group and showed allometry between size and shape and this is responsible for their relatively higher spires. The possible ecological implications of the observed pattern are discussed. It is confirmed that O. carcellesi although variable, is a clearly defined species.

The allometric growth of two groups of Nassarius vibex on beds of the bivalve Mytella charruana on the northern coast of the State of São Paulo, was evaluated between September 2006 and February 2007 in the bed on Camaroeiro Beach, and from March 2007 to June 2007 at Cidade Beach. The shells from Camaroeiro were longer and wider and had a smaller shell aperture than those from Cidade; a principal components analysis also confirmed different morphometric patterns between the areas. The allometric growth of the two groups showed great variation in the development of individuals. The increase of shell width and height in relation to shell length did not differ between the two areas. Shell aperture showed a contrasting growth pattern, with individuals from Camaroeiro having smaller apertures. The methodology based on Kullback–Leibler information theory and the multi-model inference showed, for N. vibex, that the classic linear allometric growth was not the most suitable explanation for the observed morphometric relationships. The patterns of relative growth observed in the two groups of N. vibex may be a consequence of different growth and variation rates, which modifies the development of the individuals. Other factors such as food resource availability and environmental parameters, which might also differ between the two areas, should also be considered.

Armina is the most species-rich genus of the Arminidae family with over 50 nominal species. Material of the genus Armina from the western Atlantic and the eastern Pacific was revised. Six species have been documented from the western Atlantic; however, we have determined that only four of them are valid: Armina muelleri, A. wattla, A. juliana and A. elongata. Also, only three out of seven species previously registered in the eastern Pacific were recognized in the present study: A. californica, A. cordellensis and Armina sp., an unnamed species. The phylogenetic analysis of 13 taxa and 17 characters was performed using the program PAUP (Phylogenetic Analysis Using Parsimony). The Branch-and-Bound algorithm generated a 29-step tree with the following relations: (Histiomena convolvula, (Dermatobranchus sp., ((((A. californica , (A. maculata, A. muelleri)), ((A. loveni, A. neapolitana), A. wattla)), (A. cordellensis, (Armina sp., A. juliana))), (A. tigrina, A. elongata)))). The monophyletic evidence for Armina is discussed and compared to possible speciation processes similar to those found in other Opisthobranchia groups.

An endoparasitic platyhelminth from six species of sacoglossan opisthobranchs was collected at several localities of temperate to subtropical waters in Japan. Poecilostomatoid copepods (all species of Splanchnotrophidae and several species of Philoblennidae) and a few digenean flukes had been the only endoparasitic metazoans known for opisthobranch hosts. The newly discovered parasite was 1 to 15 mm in length and had no eyes, mouth, pharynx, or intestine. It had no external organs for parasitic life (e.g. attachment organs) and inhabited the haemocoel of the host. When mature, it emerged from the host and secreted a silky substance around itself to form a cocoon. The cocoon contained egg capsules with 19–42 eggs. Larvae, hatched from the capsule, had a ciliated body and a pair of eye spots. They were negatively phototactic and capable of invading suitable hosts. These morphological and life history features suggest this parasitic worm may belong to the family Fecampiidae (Platyhelminthes: Turbellaria), one of a few obligate parasite taxa in Turbellaria. Molluscan hosts which are common for parasitic Platyhelminthes have not previously been known for this family. The newly discovered parasite may be important for understanding the evolution of parasitism in Platyhelminthes.

A new species of vesicomyid bivalve (Isorropodon nyeggaensis sp. nov.) is described based on shell morphology, from the Nyegga cold methane seep area on the Norwegian continental margin. This is the first description of vesicomyids from the Norwegian Sea and the northernmost record of recent representatives of the family Vesicomyidae. A dispersion of the genus into the Norwegian Sea basin from the north-eastern Atlantic is suggested. A brief description of other macrofauna from methane seep sites at Nyegga is also given.