Gelatinous zooplankton are an abundant and diverse group of animals in the pelagic environment. However, knowledge of species diversity and spatial distributions, as well as their ecological role, is scarce. We present information of epi- and mesopelagic gelatinous zooplankton recorded by the ‘DeepSee’ submersible between 2006 and 2012 at Isla del Coco (Cocos Island), Costa Rica, an oceanic island in the Eastern Tropical Pacific. Two species of scyphomedusae, three species of hydromedusae, two genera of siphonophores, and two species of ctenophores were observed in the videos, at depths between 50 and 400 m. None of these species had been previously recorded in the waters around the island. Furthermore, except for the jellyfish Pelagia noctiluca and a siphonophore in the genus Praya, all are new records for Costa Rican waters. This study also includes the first record of the cnidarians Modeeria rotunda, Solmissus sp., Halitrephes maasi and Apolemia spp., and the ctenophore Thalassocalyce inconstans in the Eastern Tropical Pacific. We show that surveys in regions with little information about gelatinous zooplankton may broaden our knowledge of their natural history and may result in new records of gelatinous species.

Ocean acidification (OA) is caused by increasing atmospheric concentrations of carbon dioxide, which dissolves in seawater to produce carbonic acid. This carbonic acid reduces the availability of dissolved aragonite needed for production of some invertebrate exoskeletons with potentially severe consequences for marine calcifier populations. There is a lack of public information on OA with less than 1% of press coverage on OA compared with climate change; OA is not included in UK GCSE and A Level specifications and textbooks; environmental campaigners are much less active in campaigning about OA compared with climate change. As a result of the lack of public awareness OA is rarely discussed in the UK Parliament. Much more public education about OA is needed so that people can respond to the urgent need for technological and lifestyle changes needed to massively reduce carbon dioxide emissions.

Modiolus modiolus L. (horse mussel) reefs are a priority marine habitat of high conservation value that is currently listed as endangered and/or threatened across its European distribution. Population structure, density or shell morphology may influence the biodiversity of a reef, either directly or indirectly. Thus, such metrics are important considerations for successful conservation management of these biodiversity hotspots. Population structure, shell morphology and growth rates were examined in M. modiolus reefs across the UK range of the habitat to examine differences between key populations, including those near the Lleyn Peninsula in Wales (southern range), off Port Appin in Western Scotland (mid-range) and in Scapa Flow in the Orkney Isles, Scotland (northern range). Additionally, the influence of physical conditions (temperature and tidal flow) to growth rate and predicted maximum shell length for each population was examined. Growth rates were determined using acetate peels of sectioned shells. Lower juvenile abundance was observed in Scapa Flow. Small, narrow-shaped shells were found to be characteristic of North Lleyn mussels, and larger, globular-shaped shells were characteristic of mussels in Scapa Flow and off Port Appin. Mussels in Scapa Flow were slower growing, yet reached a longer asymptotic length (L∞) than mussels of Port Appin and North Lleyn. Growth curves from sites within this study were analysed with other published data. A trend of higher L∞ at higher latitudes and at lower flow rates was observed. Variations in growth and age are discussed in relation to flow regimes, connectivity to other reefs, density and latitude.

This study reports the composition and distribution of demersal megafauna from various north-western Mediterranean submarine areas such as canyons, seamounts and landslides between 60–800 m depth, based on remotely operated vehicle (ROV) observations. From a total of 30 h of video, 4534 faunistic observations were made and analysed in relationship to environmental factors (i.e. topography, substrate type and depth). In addition, anthropogenic impact was quantified by grouping observations in four categories: fishing nets, longlines, trawl marks and other litter. The different targeted environments showed similarities in faunal composition according to substrate, depth and topography. Our results also indicated the presence of anthropogenic impact in all the sampled areas in which litter and trawl marks were the most observed artefacts.

Space is one of the primary limiting resources for organisms on the intertidal rocky shore. This paper examined the effect of reduced density on key traits (mortality and growth) on the intertidal barnacles, Chthamalus montagui and Semibalanus balanoides, on the mid-shore in Plymouth, UK. Intra- and interspecific treatments comprising of C. montagui and S. balanoides were manipulated to reduce densities at two similar sites. Changes in mortality and operculum growth were assessed over an 8-week period using digital photography. Covariates of growth included nearest neighbour distance, competition between closest pairs and initial size. Conflicting patterns were observed when comparing growth rates between treatments and sites. At Site 1, interspecific treatments had a lower growth rate than intraspecific treatments, whereas at Site 2, interspecific growth rates were higher. ANCOVA showed that nearest neighbour distance had no significant effect on growth, but when comparing differences in growth of closest neighbouring pairs, C. montagui treatment showed evidence of competition whereas S. balanoides did not. ANCOVA analysis indicated no difference in growth between each outcome of pair competition, suggesting winners are initially bigger than losers. Comparisons of mortality between treatments indicated mortality over time with no significant differences observed between treatments, but response surface methodology (RSM) revealed no effects of competition on mortality of S. balanoides, but negative effects of both intra- and interspecific competition on C. montagui survivorship. Examination of natural populations of barnacles in the mid-shore indicated there was strong spatial variation in growth rates, perhaps driven by small-scale differences within sites.

The temporal dynamics of ciliate community structure in a southern Chinese shrimp aquaculture facility were investigated during the period June–September 2012. A total of 53 species belonging to 37 genera and 17 orders were recorded based on analyses of eight samples. Ciliate abundance peaked between 16 August and 14 September 2012, while the maximum number of species occurred on 26 June 2012. Clear temporal patterns were observed in the ciliate community structure. The patterns of succession of the 10 most abundant species were consistent with the results of a Canonical Analysis of Principal coordinates (CAP) analysis. Correlation analyses showed that these patterns of succession were related to temporal changes in environmental variables. In summary, the results demonstrate that the ciliate community responds predictably to environmental variations and recovers from shrimp cultivation.

Polymastiidae (Porifera: Demospongiae) of the Nordic and Siberian Seas are revised and compared with the related species of the North Atlantic based on the morphological data from the type and comparative material and the molecular data from fresh samples. Twenty species from six polymastiid genera are recorded. Two species, Polymastia svenseni from Western Norway and Spinularia njordi from the Norwegian Sea, are new to science. One species, Polymastia andrica, is new to the Nordic Seas and two species, Polymastia cf. bartletti and P. penicillus, are new to the Scandinavian Coast. Distribution of the polymastiids in the North Atlantic and Arctic is discussed and the allegedly wide distribution of Spinularia sarsii and S. spinularia is questioned.

The polychaete assemblages inhabiting the coastal waters of the Oualidia lagoon were studied during winter 2013 and summer 2013. Taxonomic composition and diversity were determined at 43 sample sites. Among the 13 species of polychaetes recorded, 10 were newly reported for Oualidia lagoon. Hediste diversicolor and Capitella sp. were the most abundant taxa in both seasons. Temperature and salinity were higher, and chl-a and OM were lower, in summer than in winter. The structure of the polychaete assemblages was characterized by forming three main clusters, either based on sampling stations or on polychaete species. These clusters were organized according to a downstream gradient, with the stations having fine sediments and a H. diversicolor assemblage in the inner lagoon being replaced by stations with medium grain-sized sediment and a Capitella sp. assemblage in the mid-lagoon, which were in turn replaced by stations having sandy sediments and assemblages dominated by Glycera alba (winter) and P. africana (summer) in the areas closer to the lagoon inlets. The shift was, in fact, from a classical, brackish, lacunar assemblage to two different, temporal aspects of a marine assemblage (close to the inlets), with a transition assemblage in between. This corresponded with a typically paralic spatial structure whose main descriptors responded to a confinement gradient. Despite the absence of a river, the organization of the polychaete assemblages closely resembled that of an estuarine system, with the tidal regime playing a major driving role.

A new species of Laeonereis from a shrimp farm associated with a subtropical coastal lagoon on the Mexican Pacific coast is described. The new species is characterized by a deep anterior groove on the prostomium, which is shared only with L. culveri. However, longer tentacular cirri extending back to the anterior margin of chaetiger two, the number of papillae of each group on the maxillary ring of the pharynx, and the relative size of the homogomph falcigers in the new species, allow us to separate the two species. Although the species has not been previously detected in the coastal lagoon surrounding the shrimp farm, we postulate that L. watsoni n. sp. is likely to be part of the invertebrate communities of the upper parts of similar coastal lagoons that are common along the tropical coasts of Mexico.

Edible marine gastropods are consumed in northern Patagonia without regulations or knowledge of nutritional composition and food quality. We determined total lipids (TL), fatty acid (FA), paralytic shellfish poison (PSP) and metal contamination in six edible marine gastropods: Buccinanops globulosus, B. cochlidium, Trophon geversianus, Odontocymbiola magellanica, Tegula patagonica and Nacella magellanica. TL was lowest in the foot (0.29–0.56%) and maximum in organs (1.43–3.2%), presenting less TL than other edible species around the world. Saturated FA were similar to other consumed marine gastropods worldwide and dominant in all species studied (33.26–48.19%), while monounsaturated FA reached about 30% only in 2 species, but did not exceed 18% in the other species. Polyunsaturated FA reached up to 23.77%, but generally did not exceed 14%. Highly unsaturated FA (AA, EPA and DHA), reached about 27%. The dominant FA was palmitic acid (0.217 to 2.43 µg mg−1).Differences in FA could be related to the different alimentation of the species. Limit of PSP consumption was exceeded in a few months only for two species. Lead was not detectable (<4 µg g−1) while cadmium ranged from 0.07 to 15.32 µg g−1. Our results can be useful to ensure the safety food of these resources, which are being consumed and exported in low quantities in Argentina, but may be commercialized massively in the near future. Monitoring these and other food resources is essential and should be performed in any established fishery of the species reported here to guarantee the safety human consumption.

Some Antarctic littorinoideans have a remarkable convergence with Naticoidea in shell and operculum features. Two naticid-like species of that group are studied in their phenotypic features in order to improve their taxonomy and to discuss the meaning of that convergence, as the former are herbivore-detritivore and the latter active predatory organisms. One of the studied species is the littorinid Laevilacunaria antarctica (Martens, 1885). The other belongs to a new genus – Pseudonatica, with the type species also newly described: P. antarctica, the genus is tentatively placed in Zerotulidae. Another Pseudonatica is also described, P. ampullarica, based only on shells collected by Marion-Dufresne French expedition off Brazilian coast, this finding expands the occurrence of zerotulids northwards. Besides the similarities of shell and operculum, other structures of these Antarctic species also show singular similarities with naticoideans, such as the wide foot, the complexity of opercular attachment in pedal opercular pad, the wide oesophageal gland, and the coiled arrangement of the pallial oviduct. The phenotypic characters were coded and inserted in a previous large phylogenetic analysis on Caenogastropoda (Simone, 2011), furnishing a wide basis for discussion on the characters, taxonomic position, evolution and adaptations of these organisms.

Octopus mimus is the main octopus targeted by the small-scale fishery in the Eastern Pacific. Commercial catches of octopus from the Reserva de Producción Faunística Marino-Costera Puntilla de Santa Elena (REMACOPSE) Marine Protected Area in Ecuador were sampled from July to December 2013 in order to describe the reproduction and population structure of this octopus. The 4171 sampled octopuses ranged from 56 to 250 mm in mantle length (ML) and 45 to 3178 g in body weight (BW). Mean octopus weight did not change monthly. Males were mostly mature while the majority of females were immature. Presence of some mature and a few spent females in all months sampled suggests that the population shows an extended spawning period. No spawning peak could be properly defined. Sex ratios did not significantly shift from the expected 1:1 in most samples. Females mature at a larger size (1234 g, BW; 165 mm, ML) than males (487 g BW; 114 mm ML). We recommend considering a minimum legal size of 1200 g BW. A year-long sampling programme for O. mimus should also be completed in order to detect any spawning peak.

Saline lagoons are priority habitats in the United Kingdom supporting several protected specialist species. One specialist, the amphipod Gammarus insensibilis, is infected with behaviour-altering microphallid trematodes such as Microphallus papillorobustus. In saline lagoons around the coast of England (Gilkicker and Lymington–Keyhaven on the Hampshire coast and Moulton Marsh in Lincolnshire) there is variation in the prevalence of this parasite in the gammarid populations (0 at Salterns in the Lymington–Keyhaven lagoon system to 98% at Gilkicker). Infection intensity ranged from 0 to 20 metacercariae in individual amphipods. Higher infection intensity can alter the shape of the amphipod's head. Under experimental conditions respiration rate is significantly reduced in infected animals and reproductive output (expressed as early stage embryos mg g dry weight−1) is significantly lower in infected females. It is important to consider the role of host–parasite interactions in order to understand the ecology of specialist lagoon species such as G. insensibilis and their lagoon habitats.

Two new species of Clausidium copepods were collected on the bodies of ghost shrimps from the Iranian coast of the Gulf of Oman. Clausidium makranensis sp. nov. and Clausidium sarii sp. nov. are described from the large chelipeds of Neocallichirus natalensis and Corallianassa martensi, respectively. Clausidium makranensis sp. nov. is distinguishable from its congeners by the unique anal somite that is armed with sclerotized hooks on each side. Clausidium sarii sp. nov. can be differentiated from its congeners by the armature and shape of leg 5.

Marine benthic populations are dependent on early life-history stages surviving multiple population bottlenecks. Failure at one or several of these bottlenecks can alter species’ patterns of distribution and abundance. The barnacle Semibalanus balanoides is found along temperate and sub-arctic shorelines of the Atlantic and Pacific Oceans. Over the past century the southern range limits of S. balanoides have shifted hundreds of kilometres poleward on both coasts of the Atlantic. Here we tested if temperature limits fertilization and used these data, along with those from previous studies, to create mechanistic biogeographic models to understand which potential population bottlenecks in the early life-history of S. balanoides influence its distribution and abundance. In the western Atlantic survival of new recruits is probably more important in setting the southern range limit than the effects of temperature on early life-history stages because fertilization, brooding and the probability of larval release matching phytoplankton availability were all predicted to be high near the historical range edge. Phytoplankton mismatch may partially explain the ephemeral nature of S. balanoides in some parts of the English Channel. Further south along the coast of France predicted brooding success was reduced in a pattern consistent with historical range shifts in this region. Within Galicia, Spain fertilization was predicted to be low near the southern limit, and likely plays an important role in setting this range edge. Mismatches between phytoplankton abundance and larval release in Galicia may further limit reproductive success within this region.

The Atlantic–Mediterranean transition zone between the Alborán Sea and the Gulf of Cádiz constitutes the most prominent marine geographic barrier in European waters and includes known phylogeographic breaks such as the Strait of Gibraltar and the Almería-Oran Front. A genetic shift in this area has been previously documented for the European littoral shrimp Palaemon elegans. Here we carried out a phylogeographic analysis with the congeneric and sympatric species Palaemon serratus to test for similar intraspecific genetic differentiation and geographic structure. This littoral prawn is distributed in the Northeastern Atlantic Ocean, the Mediterranean Sea and the Black Sea. We compared DNA sequences from the mitochondrial genes Cox1 and to a lesser extent from 16S rRNA of several Atlantic and Mediterranean populations. Furthermore, sequences from the nuclear gene Enolase were included for corroborating differences between Mediterranean and Atlantic individuals. A pronounced genetic differentiation was detected between the Mediterranean and Atlantic populations, amounting to 10.14% in Cox1 and 2.0% in 16S, indicating the occurrence of two independent evolutionary lineages. Interestingly, specimens from the Atlantic Gulf of Cadiz cluster together with the Mediterranean individuals, indicating that a biogeographic barrier appears to be located west of the Strait of Gibraltar.

The complete larval development of the lobster shrimp Leonardsaxius amurensis (Kobjakova, 1937) (Decapoda: Axiidea: Axiidae) is described and illustrated for the first time. The first zoeae of this species were collected from the plankton samples and reared in the laboratory before moulting to the megalopa. A molecular genetic analysis based on comparison of partial mitochondrial COI, 12S rDNA and 16S rDNA sequence data confirmed the identity of axiid larvae found in the plankton and L. amurensis adults collected in the same area. The larval development of L. amurensis includes five zoeal stages and a single megalopa. Zoeae I of L. amurensis are characterized by the presence of one short posterodorsal spine on the fifth pleonite in contrast to the larvae of related sympatric species Boasaxius princeps having four posterodorsal spines on the pleonites 2–5. Leonardsaxius amurensis occupies an intermediate position between lobster shrimps with abbreviated pelagic development (2–3 zoeal stages) and species with long development (up to eight zoeal stages). Thus, the number of zoeal stages in the family Axiidae varies widely, similarly to that in the families Callianassidae and Upogebiidae.

A short-term Jolly–Seber mark-recapture model experiment is described. This experiment was aimed at estimating the rate of catch per unit effort (CPUE) and the catchability coefficient (q) of the Atlantic blue crab (Callinectes sapidus) in the fishing port of Sisal, Yucatan, Mexico. To estimate the local population size, 52 traps were deployed along four transects located in a coastal capture area of 3600 m−2. The CPUE and q were compared between the daily mark-recapture Jolly–Seber experiment and the bi-monthly (carried out every 2 months) samplings. The average abundance was estimated at 3475 individuals. All three suggested scenarios, applied to estimate densities, gave similar estimates, i.e. 0.0386, 0.0350, 0.0365 crabs m−2 for the first (Previously Cited Attraction Radius), second (CPUE per transect) and third (Catchability-Density Relationship), respectively. Based on the latter scenario, densities ranged from 27,900 (annual average) to 36,500 (Spring) crabs km−2. The average CPUE of the daily mark-recapture experiment was estimated at 1.96 crabs trap−1, whereas the average bi-monthly CPUE was estimated at 1.13 crabs trap−1. The q (per trap) was estimated at 0.0186 for the daily mark-recapture experiment and at 0.0247 for the bi-monthly sampling. Both catchability and CPUE increased in individuals whose size ranged between 110 and 170 mm CW. However, no significant difference (ANCOVAs) was found between the daily and bi-monthly samplings neither in CPUE nor in catchability. The use of both mark-recapture data and the Jolly–Seber model proved to be a fast and reliable method for estimating the abundance and catchability of Atlantic blue crab.

This study constitutes a first attempt to investigate sex differences in osmoregulatory capacity and metabolic responses in relation to hyper- and hypo-osmoregulation in the intertidal euryhaline crab Uca tangeri. Adult male and female specimens from Cadiz Bay, Spain (36°23′–37′N 6°8′–15′W), were acclimated to three different environmental salinities (12, 33 and 55 psu) during 7 days, and several parameters were assessed in haemolymph (osmolality, glucose, amino acids, triglycerides and lactate) as well as in metabolic key organs (hepatopancreas, anterior and posterior gills: glycogen, free glucose, amino acids and triglycerides). Specimens from both sex exhibited high and similar hyper- and hypo-osmoregulatory capacities. However, metabolite levels were differentially affected upon acclimation to low and high salinity in several metabolic organs and haemolymph of male and females: (i) glycogen in gills, (ii) free glucose in gills and hepatopancreas, (iii) amino acids in hepatopancreas, (iv) triglycerides in haemolymph, hepatopancreas and posterior gills, and (v) lactate in haemolymph. The results suggest the occurrence of differential metabolic adjustments upon hyper- and hypo-osmoregulation related to sex in the intertidal euryhaline crab U. tangeri.