The movement and activity patterns of the nurse shark, Ginglymostoma cirratum, a vulnerable species off Brazil, were investigated using mark-recapture and acoustic telemetry at an oceanic insular Marine Protected Area, the Fernando de Noronha Archipelago, Brazil. A total of 93 sharks were captured and tagged, ranging from 82 to 265 cm of total length (TL). Nurse sharks were captured throughout the year, and all life-stages used the insular shelf. Fifteen sharks (16% of the total) were recaptured after periods at liberty ranging from 3.5 h to 705 days, and the distances between tag and recapture locations ranged from 0.07 to 3.5 km. Site fidelity and movements of 10 sharks ranging from 107 to 265 cm TL were investigated for 18 months with an array of automated telemetry receivers. The mean period of detection of the monitored sharks was 66 days, ranging from 13 to 119 days. One individual 158 cm TL was monitored with active tracking for 17 days, with distances between daily locations ranging from 0.84 to 3.32 km, exhibiting movements similar to those of sharks monitored by automated telemetry. Despite remaining motionless or exhibiting short range movements for several hours or days, nurse sharks can be relatively wide-ranging, and protected areas alone cannot be the only conservation measure used to protect this species, which requires a set of protective measures, including fisheries management.

The primarily bathypelagic gonostomatid Cyclothone microdon, amongst the most abundant of all vertebrates, remains poorly known. We describe its diet in The Gully, a very large submarine canyon off Nova Scotia, Canada, based on the stomach contents of specimens caught by midwater trawl. In The Gully, C. microdon had a shallower distribution than in open ocean and primarily fed at mesopelagic depths. Most of its diet comprised vertically migrant calanoid copepods, while its secondary prey was conchoeciinid ostracods. Both were typical of the food eaten in other regions by its mesopelagic congeners and were consistent with the results of the only previous dietary study of C. microdon.

Currently, little is known about the helminth fauna in sirenian species. Therefore, the objective of this study was to assess the frequency of infection by Pulmonicola cochleotrema in Antillean manatees (Trichechus manatus manatus), in the North-eastern region of Brazil. Between the years of 1989 and 2014, 88 manatees found on the North-eastern Brazilian coast were clinically examined. They included animals that were found dead, animals maintained in captivity and specimens reintroduced into conservation areas. During their physical examination, helminths present in necropsied carcasses and in reintroduced animals were collected, as well as faecal samples. Parasites were detected in 7.95% (7/88) of the animals; all specimens collected being identified as P. cochleotrema. Only adult manatees were infected, and in two cases clinical signs were observed. This is the first report on the occurrence of P. cochleotrema in Antillean manatees in the states of Paraíba and Sergipe, in the North-eastern coast of Brazil.

Despite the ecological relevance of tropical reefs, information on species composition and coverage on sandstone reefs is very scarce. Most studies on reef systems have been conducted for true coral reefs, ecosystems that show calcareous formations with extensive coral cover and diversity. The aim of this study was to analyse the coverage of benthic assemblages in a submerged sandstone reef (22–24 m) in a relatively non-explored region (Tropical South-western Atlantic). In this area, filamentous algae (43.6%) and sponges (19.6%) are the main components of the benthic reef assemblages. Other benthic reef fauna (ascidians, corals and zoanthids) showed lower coverage, although their importance may vary depending on the area. A negative correlation between filamentous algae and slow-growing reef-building organisms (calcareous algae) was observed. High sand coverage (19.6%) over the reef revealed a high rate of silting. A low coral diversity (only two resilient species) was quantified, and most of the coral colonies were small-sized. The results provide a baseline assessment for a poorly known ecosystem with turbid-water benthic communities and higher sea-surface temperatures near the Earth's equator.

The lagoon of El Bibane (Tunisia) is a Mediterranean coastal area that is affected by an increasing human impact. Thus, an estimation of its biodiversity and an ecological quality assessment are very urgent. This study investigates the meiofaunal and nematode communities of the El Bibane lagoon both from a taxonomic and a functional point of view. Nematodes were the dominant group as is common in brackish water systems. The nematode community was made up of 62 genera in 22 families. Xyalidae, Chromadoridae and Cyatholaimidae were the richest and most abundant families. The taxonomic composition and biodiversity of nematodes were comparable to those found in other European and Mediterranean transitional areas. Both meiofauna and nematodes showed a clear subdivision between marginal and central areas. The central stations, represented by fine sediments and higher amounts of organic carbon, seemed to be characterized by low meiofaunal densities, nematode diversity and a strong dominance of 1B and 2B trophic guilds. These trends could be related not only to the grain size and organic load, but also to a possible influence of tidal currents that can transport pollutants in the central area of the lagoon coming from the adjacent coastal areas. Shannon diversity and life strategies are not always in agreement in defining the ecological quality, but an overall worse ecological quality was detected especially at S6. The results of this study are an important starting point for the future monitoring of the potential and actual human impact on the El Bibane area over time.

Studies on the quantitative distribution of cephalopods in the Arctic are limited, and almost completely absent for the Barents Sea. It is known that the most abundant cephalopods in the Arctic are Rossia palpebrosa and Gonatus fabricii. Their biomass and abundance have been assessed for the first time in the Barents Sea and adjacent waters. The maximum biomass of R. palpebrosa in the Barents Sea was 6.216–6.454 thousand tonnes with an abundance of 521.5 million specimens. Increased densities of biomass were annually registered in the north-eastern parts of the Barents Sea. The maximum biomass of G. fabricii in the Barents Sea was 24.797 thousand tonnes with an abundance of 1.705 billion specimens. The areas with increased density of biomass (higher than 100 kg km−2) and abundance (more than 10,000 specimens km−2) were concentrated in deep-water troughs in the marginal parts of the Barents Sea and in adjacent deep-water areas. The biomass and abundance of R. palpebrosa and G. fabricii in the Barents Sea were much lower than those of major taxa of invertebrates and fish and than those of cephalopods in other parts of the World Ocean. It has been suggested that the importance of cephalopods in the Arctic ecosystems, at least in terms of quantitative distribution, could be somewhat lower than in the Antarctic or the tropics. Despite the impact of ongoing warming of the Arctic on the distribution of cephalopods being described repeatedly already, no impact of the current year's climate on the studied species was found. The only exception was the abundance of R. palpebrosa, which correlated with the current year's climate conditions.

Wedge clam, Donax scortum occurrence was studied from February 2009 to January 2010 in Padukere sandy beach, Karnataka (India). The following biological parameters were measured in 2367 individuals of the wedge clam, Donax scortum: length, breadth, width, total weight, shell weight, wet meat weight, dry meat weight and number of clams. The calculated linear equation of length-breadth and length-width relationships were B = 3.5968 + 0.5421L and W = 0.8191 + 0.4345L respectively. The length-total weight, length-wet meat weight, length-dry meat weight and length-shell weight relationships were 0.0001414L3.0224, W = 0.0000037L3.5204, W = 0.0000011L3.4513 and 0.0000852L2.9912 respectively. The values of correlation coefficient for different shell dimensional relationships were very close to unity. It was clear from the study that the most ideal period for clam harvest was April, June and December, especially when condition index was maximum. Length showed a strong correlation with silt and clay. Dry meat weight was negatively correlated with air temperature. Shell weight showed positive correlation with length, breadth, width and dry meat weight, and abiotic parameters, silt and clay. Condition index was positively correlated with electrical conductivity, whereas it was negatively correlated with dissolved oxygen. It showed a strong positive correlation with salinity. Seasonal fluctuation of condition index in D. scortum was probably related to reproductive activity. The harvesting of wedge clam could be carried out considering the maximum sustainable yield without over-exploitation

For the management of mollusc resources, knowledge of various population parameters and exploitation level of the population of wedge clams are needed. Population dynamics on wedge clam, Donax scortum is still unknown in Asia. FAO-ICLARM Stock Assessment Tools (commonly known as FiSAT) was used for calculating population parameters of this species. The specimens of D. scortum were collected from Padukere sandy beach at monthly intervals from February 2009 to January 2010. Asymptotic length (Lα) was 70.88 mm and growth coefficient (K) was estimated at 0.64 year−1. The sizes attained by D. scortum were 33.51, 51.17, 60.49, 65.40, 67.99 and 69.36 mm at the end of first, second, third, fourth, fifth and sixth years of age, respectively. Density of clams ranged from 2 ind. m−2 (June, July and August) to 8 ind. m−2 (December). Biomass (total weight) of clams ranged between 10.084 g m−2 (August) to 185.100 g m−2 (December). Total mortality (Z) for D. scortum was 3.20 year−1. Natural mortality (M) and fishing mortality (F) were 0.64 year−1 and 2.56 year−1 respectively. Exploitation level (E) was computed as 0.80, indicating that the fishery of D. scortum in the coastal waters of Karnataka is overexploited.

In this paper, metamorphosis of laboratory-reared cyprids of the pedunculate cirripede, Capitulum mitella was successfully induced. A timeline and a detailed description of morphological events during metamorphosis were derived from light microscopy and scanning electron microscopy analyses. The metamorphic process of cyprids involves five main events. (1) Triggering of metamorphosis: after 0–6 h of reagent exposure, the epidermis ventral to the compound eyes gradually invaginates. (2) Invagination and separation of epidermis: after 6–36 h, the invagination bypasses the compound eyes, the cypris epidermis separates slightly from the carapace and the nauplius eye gradually migrates ventrally. (3) Formation of juvenile rudiment: after 36–72 h, the metamorphosing specimen shape slightly resembles that of a juvenile. (4) Shedding of thoracopodal exuvium: after 72–96 h, the cyprid finally sheds the thoracopodal exuvium and metamorphoses into a juvenile barnacle. (5) Early development of juvenile barnacle: the juvenile shed the cirrum cuticle for the first, second, third and fourth time at 1.5–2, 1.5–2, 4–5 and 5–6 days, respectively. The newly formed juvenile completely assumes the shape and armature of all shell-plates found in adult barnacle. Rostro-carnal length of the juvenile is 240–260 μm. Tergum, scutum and upper latus are paired, and carina and rostrum are unpaired. Uniform circular depressions are dispersed on the surface of the tergum, scutum and carina. The rostrum and upper latus, which have the shape of small triangle, are not clear. The entire surface of the peduncle is covered with convoluted cuticular ridges. The metamorphosis of C. mitella is similar to that of Lepas.

Polychaete abundance and assemblage structure were analysed from 144 zooplankton samples taken in eight seasonal campaigns between October 2007 and November 2008 on Babitonga Bay estuary (south Brazil). A total of 16 taxa were found, classified in three categories: (i) larvae (five taxa) dominated by Loimia sp. (Terebellidae) (up to 59 ind 100 m−3); (ii) syllid epitokes (three taxa) dominated by Procerastea sp.2 (up to 11 ind 100 m−3) and Myrianida sp. (up to 6 ind 100 m−3); and (iii) adults of typically benthic species (eight taxa) which were only occasionally sampled in low densities (<1 ind 100m−3). Larvae dominated mostly during spring and summer in the outer sector of the estuary, while syllid epitokes peaked during winter with higher abundances in the inner sector. The assemblage dynamics match the seasonal and spatial changes in the environmental conditions of the estuary. Descriptive variables explained 49.5% of the polychaetes variance according to Redundancy Analysis. Rainfall, temperature and salinity were the variables most influencing the assemblage, with rainfall and temperature regulating seasonal, and mostly salinity regulating spatial patterns, similar to meroplanktonic populations from both temperate and tropical latitudes. Dominant species had different hydrographic preferences, Loimia sp. was more abundant in warmer (>23°C) and saltier (>25) waters, Magelona papillicornis larvae were more abundant in saltier waters with intermediate temperatures (22–23°C), and the syllids were more common and abundant on lower temperatures (<20°C). In addition we highlight the occurrence of several benthic taxa suspended in the water column, probably due to bottom disturbance.

High plasticity in cephalopod populations shows dramatic changes in their biological traits. Commercial catches of Mayan octopus (Octopus maya) in six localities of the state of Campeche, Mexico, were sampled monthly for five consecutive fishing seasons (2005–2009) in order to describe variations in population structure and maturation. Octopus maya grows and matures during the fishing season, from August to December. Spent individuals predominate in January and February, revealing a year-long life cycle. However, the presence of a few spent females in all months sampled suggests that a small part of the population shows an extended spawning period. Overall sex ratios did not significantly shift from the expected 1:1 in most samples. Males are mostly mature while the majority of females are immature during the season. Use of illegal fishing gears (spear diving or pots) in central localities accounts for a larger share in mature females. Octopus size showed large interannual and geographic differences. Females mature at a larger size (1024 g body weight, BW; 124 mm mantle length, ML) than males (484 g BW; 91 mm ML). Size at maturity in both sexes varies more between seasons than between localities. Female ML at maturity is larger than the current minimum legal size and implications for current octopus fishing regulations are discussed.

It is necessary to monitor shell-associated polydorid worms owing to the risk that they pose to commercially important molluscs. This requires accurate identification, but is often hampered by morphological similarities among species, insufficient type specimens, and abridged species descriptions. Thus morphological characteristics and molecular sequences of the most harmful polydorid species, Polydora uncinata from Japan and Australia and Polydora hoplura from South Africa were compared to determine whether they represent two morphologically similar, but genetically distinct species, or a single species. A wide range of morphological variation (with respect to size, length of caruncle and pigmentation patterns) was observed in each species and population, and their variations largely overlapped and revealed them to be at the intraspecific level of a single species. This was confirmed by gene sequences of nuclear 18S and 28S rRNA that were completely identical for P. uncinata and P. hoplura. The mitochondrial 16S rRNA and cyt b gene analyses also showed no genetic differences between these two species. The tree topology of the mitochondrial cyt b gene did not reflect geographic differences but instead suggests artificial transportation of the species. We recommend the synonymization of P. uncinata with P. hoplura.

During ArcticNet surveys aboard ‘CCGS Amundsen’ in 2011, several subtidal stations located in Canadian Archipelago were sampled in order to study the composition of their benthic communities. Among the abundant material sampled, several specimens of rare polychaete species were found. Examination of this material showed four species not previously recorded in the area, and a new species described herein. Descriptions of these specimens are given in this work. Ophelina brattegardi Kongsrud et al., 2011 is characterized by a body composed of 27–28 chaetigers, by having the parapodia of the last four chaetigers shifted to the ventral side of the body, and by lacking branchiae in mid-body chaetigers. Macrochaeta polyonix Eliason, 1962 is unique within the genus in having several (instead of one or two) compound neurochaetae in anterior parapodia. Chaetozone acuta Banse & Hobson, 1968 is characterized by having spines from anterior third of the body and arranged in bundles composed of just a few chaetae. Chaetozone jubata Chambers & Woodham, 2003 can be distinguished from similar species by having very long capillary chaetae from chaetiger 2 or 3. Finally, Dialychone hervyae n. sp. is characterized by bearing four pairs of radioles with narrow flanges, by the bilobed tip of its first peristomial ring that projects beyond the collar, and by the paleate thoracic notochaetae bearing long mucros.

Three new species of paramunnid isopods are described: Pentaceration pleonarietis sp. nov., Neasellus argentinensis sp. nov. and N. bicarinatus sp. nov. The three species were collected off Buenos Aires province, the last one was also collected off Chubut province, Argentine Sea. The species belonging to Pentaceration represents the first record of this genus in the Argentine Sea. The diagnostic characters of the genus Neasellus are revised and besides the inclusion of the two new species herein described, a new combination for the species Pelagogonium oculatum Schultz, 1977 is proposed.