The introduction of the Manila clam into British coastal waters in the 1980s was contested by conservation agencies. While recognizing the value of the clam for aquaculture, the government decided that it posed no invasive risk, as British sea temperatures would prevent naturalization. This proved incorrect. Here we establish the pattern of introduction and spread of the species over the first 30 years of its presence in Britain. We report archival research on the sequence of licensed introductions and examine their relationship in time and space to the appearance of wild populations as revealed in the literature and by field surveys. By 2010 the species had naturalized in at least 11 estuaries in southern England. These included estuaries with no history of licensed introduction. In these cases activities such as storage of catch before market or deliberate unlicensed introduction represent the probable mechanisms of dispersal. In any event naturalization is not an inevitable consequence of introduction and the chances of establishment over the period in question were finely balanced. Consequently in Britain the species is not currently aggressively invasive and appears not to present significant risk to indigenous diversity or ecosystem function. However it is likely to gradually continue its spread should sea surface temperatures rise as predicted.

An oceanographic cruise conducted during June 2008 in the Gulf of Gabes revealed the existence of different water masses; the Modified Atlantic Waters (MAW) circulated in the upper 100 m in the offshore area, the Mixed Mediterranean Water (MMW) was confined to the inshore region and the Ionian Water (IW) was in deep offshore water. The thermal stratification was indicated by the vertical profiles of temperature generated from a coast-offshore section. Phosphorus limitation was induced by the thermal stratification as shown by the high N/P ratio. Heterotrophic and mixotrophic dinoflagellates were the major contributors to total phytoplankton biomass. Ciliates were less abundant and dominated by tintinnids. Small planktonic copepods (≤1.45 mm) contributed to 93.64% of total copepod abundance in the inshore area as a result of the high density of Oithona similis, Oithona nana, Clausocalanus furcatus and Euterpina acutifrons in this area characterized by warm and salty MMW. In fact, small copepods were significantly correlated to both temperature and salinity. Small copepod fraction prevailed also in the MAW contributing to 71.05% of total copepod abundance as a result of the dominance of O. nana and C. furcatus. Nonetheless, the large copepod Nannocalanus minor was more adapted to the deep IW where it contributed to 44.05% of total copepod abundance. Invasive species were encountered in the offshore region intruded by the Atlantic waters. The Atlantic copepods were scarce and less abundant reflecting the weakening of the Atlantic flow in the eastern basin of the Mediterranean.

The pearl oyster, Pinctada radiata, shows great variation in shell morphology throughout its distribution. This variation can be related to phenotypic plasticity, genetic variability or a combination of both. Using geometric morphometric and microsatellite DNA analyses, two morphologically distinct populations of the pearl oyster were studied in the northern Persian Gulf, i.e. from the Lavan and Hendourabi Islands. Ten landmarks were selected to define the shape of the left shell. In addition, concentration of Zn, Mg, Fe, Cu, Pb, Cd, Mn and Cr of the soft tissues were measured using atomic absorption spectrometry. Six microsatellite loci were used to assess the population genetic structure of the pearl oyster. There were morphometric differences between the populations suggesting the existence of two morphotypes. There was a significant difference between the two populations in concentrations of Fe, Mg, Zn, Cd, Mn and Cr indicating that the specimens from the Lavan Island experience a more stressful environment than those from the Hendourabi Island. Analysis of molecular variance (AMOVA) indicated that the proportion of the genetic variation attributed to differences among populations of the pearl oyster was highly significant for both FST and RST (FST = 0.066, RST = 0.265, P < 0.001). Our findings showed that stressful conditions resulting from heavy metals may have a direct influence on the separation of the populations in Lavan and Hendourabi despite the lack of a physical barrier.

Species definition is not an easy task, when considering the more than 27 known species concepts. Among them, the morphospecies concept has been one of the most applied since it is based on the use of observable morphological features. Morphometry has been used to delimitate morphospecies or similar taxa complementing the morphological observations and contributing to clarify taxonomic problems. Specimens from the sympatric species Perinereis anderssoni and Perinereis ponteni, collected from the north-eastern to southern coast of Brazil and considered synonymous by some authors, were compared through morphometric analyses for the evaluation of their taxonomic status. Morphometric analysis indicates that notopodial cirri lengths in the median and posterior regions on the body clearly allowed differentiation between the two species. Our results indicate that the number and arrangement of paragnaths demonstrate a pattern of variation that effectively differs and could be used to discriminate these two Perinereis species. This distinction was confirmed by the restricted among-population variability within each species, even when populations that are geographically very distant from each other were considered.

Greenland has more than 200 years of history of studies of the sponge fauna and is the type locality for a number of species. Many of these have not been encountered since, and as the type material has been hard to find or even lost, their taxonomic status has remained uncertain. In this study all species of calcareous sponges previously reported from Greenland are reviewed. The revision is based predominantly on new or unidentified material collected during various expeditions, but also on material used by previous authors. This includes samples from all coasts of Greenland, from the southernmost Kap Farvel area to Peary Land on the northern coast, some of the northernmost records of calcareous sponges ever. Greenland is a transition zone between the western and eastern Atlantic boreal calcareous sponge faunas, being home to species from both sides of the North Atlantic combined with some true Arctic species. There is also a strong link between the Canadian and Greenlandic sponge faunas. Twenty-eight species have been identified, from which six are new to Greenland and one is new to science. New records for Greenland are: Clathrina arnesenae (Rapp, 2006); Clathrina camura (Rapp, 2006); Clathrina pellucida (Rapp, 2006); Sycon abyssale Borojevic & Graat-Kleeton, 1965; Leucandra valida Lambe, 1900; and Sycettusa thompsoni (Lambe, 1900). Clathrina tendali sp. nov. has been described from western Greenland and Leucosolenia corallorrhiza (Haeckel, 1872) and Leucandra penicillata (Schmidt, 1869) have been resurrected. Keys for identification of higher taxa and the different species of Greenlandic Calcarea are provided.

Density distribution of the common infaunal bivalves, Macoma balthica and Cerastoderma edule, was studied along the Murman Coast of the Barents Sea during 2002–2010. In both species, abundance was generally higher in West Murman in contrast to East Murman. Highest density of Macoma balthica reaching 1535 ind. m−2 was observed in the Kola Inlet. Cerastoderma edule was less abundant; its density rarely exceeded 10 ind. m−2 in all but one site, where 282 ind. m−2 was registered. Reconstruction of abundance distribution across the European geographic range of Macoma balthica revealed that it does not match an ‘abundant-centre’ pattern, having features of ramped north. On the other hand, distribution of Cerastoderma edule abundance across the range generally follows an ‘abundant-centre’ pattern but southern edge populations show relatively higher abundances as compared with those at the north edge (the Barents Sea).

Patagonema iubatum gen. nov. sp. nov. is described from a sandy beach at Playa Pozo, Golfo Nuevo, Argentina. It resembles Oncholaimidae (Nematoda: Enoplida) and it is characterized by a buccal cavity comprising a combination of three teeth and three mandibular ridges with small teeth. The new genus is also characterized by the presence of papillose pre-cloacal supplements, cephalated spicula and a gubernaculum with dorsal apophysis and lateral piece, and a new demanian system configuration. Patagonema iubatum sp. nov. has 9–11 papillae-like pre-cloacal supplements, short and cephalated spicula and a gubernaculum with dorsal apophysis and pointed lateral piece. Its position inside Oncholaimidae is discussed.

A new species from the subfamily Comesomatinae is described from the back-reef platforms of the central part of the Maldivian archipelago. Paracomesoma susannae sp. nov. is characterized by a large-sized body, very long cephalic sensilla (72–91 µm long), lateral differentiation of punctuations, and, in the males, 19–22 minute precloacal supplements, relatively short spicules (2.3–2.9 anal body diameter) and a hook-like structure in the distal end of the gubernaculum. Paracomesoma susannae sp. nov. is the only species so far described of the genus which appears to have such a low ratio of the outer labial and cephalic sensilla (about 0.02). An emended diagnosis of P. paralongispiculum is proposed, along with an updated and modified key to all the valid species of the genus Paracomesoma.

A comparison is made of sponge diversity and abundance in nine cold-water coral reef locations situated in four regions of the north-east Atlantic, Rockall Bank (two reef locations, both deep, oceanic), Porcupine Bank (two locations, both deep, oceanic), Mingulay (two reef locations, both shallow, near-shore), Skagerrak (three reef locations, all shallow, near-shore). Literature data from two reefs were used to supplement our own data from seven reef locations. Geographical distance between the regions may be summarized as Rockall Bank < Porcupine << Mingulay <<< Skagerrak. The first three regions are all situated west of the British Isles, and prevailing current patterns and bottom conditions would make direct larval transport between all three a distinct possibility. The fourth region, Skagerrak, is situated away from the Atlantic regions, with larval contact hampered by long distances over predominantly shallow sedimented sea bottoms. Accordingly, we expected the largest taxon turnover to be between the three Atlantic regions and the Skagerrak localities. However, cluster analysis and multidimensional scaling clearly show, that shelf reefs at Mingulay were faunistically closer to the geographically- distant shelf reefs at Skagerrak than to the geographically closer bathyal reefs of the Porcupine–Rockall area. Further research is necessary to determine whether depth is a proxy for other abiotic factors such as oceanic circulation or trophic conditions.

Size frequency distribution, catch per unit effort (CPUE) and biomass of blue swimming crab Portunus segnis were studied in the northern Persian Gulf. A total of 1689 male and 1824 female crabs were collected by swept area method on a monthly basis from May 2010 to September 2012. The populations of male and female crabs were dominated by adult crabs (carapace width >100 mm) from December to May. The juvenile crabs were dominant from June to October and the averages of CPUE did uptrend from June to October. The CPUE increased in full moon and the highest value was observed in shallow coastal areas below 10 m and significantly decreased as depth increased. The maximum CPUE was recorded at 415 and 450 engine powers and the vessel speeds of about 2.5 and 2.8 knots. The monthly biomass estimations showed an upward trend from June to October within the study period, so that the maximum biomass was 110 tonnes in October 2011. Given the CPUE trend and biomass estimation, the results of the present study suggest that October is the optimum time as open fishery season for blue swimming crab in the northern Persian Gulf and the highest CPUE is achievable in shallow coastal areas at less than 10 m depth.

A new species of Ampharetidae, Anobothrus amourouxi sp. nov., has been identified from bathyal depths of the Capbreton Canyon, Bay of Biscay (NE Atlantic Ocean). This new species is characterized by inner branchiae with transversal ciliated ridges, notochaetae from modified eighth thoracic unciniger with hirsute tips, uncini from thoracic unciniger with 6–7 teeth in lateral view arranged in two vertical rows in frontal view, fused segments II + III with paleae from SII and reduced notopodia without chaetae from SIII. An identification key for all hitherto described species of the genus Anobothrus is provided.

The Mediterranean Sea is currently under siege by a conspicuous alien pressure, and, within some families (e.g. the Ostreidae), the number of native species seems to be remarkably outnumbered by that of the alien ones. We wanted to test the reliability of the molecular data currently available on the small alien oysters recently invading the Mediterranean Sea. Samples from Greece and Turkey, encompassing the known species-specific morphological variation, were sequenced for the markers with the widest taxonomic coverage in the group of small oysters (i.e. the 16S rDNA and the COI). The sequences obtained have been compared with those available in GenBank, and a possible identification at the species level has been finally tested in a DNA-barcoding fashion. The present results clearly demonstrated that our samples belong to a single, morphologically highly variable species. Their 16S sequences were closely related to a sequence registered under the name Dendostrea folium, with a genetic distance which does not warrant conspecificity. Additionally, a remarkable number of sequences retrieved from the GenBank (of both genes) did not form a monophyletic group according to the published classification of the vouchers, suggesting—at least in part—an origin from specimens not properly identified. Both genes seem promising for use as DNA-barcode, although the COI will probably prove more effective. Therefore, we urge the availability of a baseline of oyster pedigreed DNA barcode sequences in the public databases, to allow the use of such genetic data to reliably monitor bio-invasions in the Mediterranean Sea.

This study examines the effect of water temperature on the formation of shell sculpture in young molluscs of the genus Hiatella. The larvae of H. arctica and H. gallicana were maintained under laboratory conditions at different temperature regimes. The animals were reared from late veligers to juveniles with a shell length of 700 μm. The results of the experiment showed that the shell sculpture, which is a diagnostic species character, was developed to various degrees at different temperatures. The larvae of each species grew to juveniles with variously pronounced shell sculptures ranging from a complete absence of sculpturing to its maximum development. The individuals with smooth shells like those of H. gallicana were the most abundant among the molluscs reared at +5°С. At +12°С, all molluscs formed ridges and two rows of long spines in the posterior portion of the shell, which is typical for H. arctica. At +8°С, the molluscs developed various intermediate forms of shell sculpture. It was, therefore, demonstrated that the development and prominence of shell sculpture is determined by environmental temperature. These results are discussed with regards to the validity of using shell sculpture as a taxonomic character for species in the genus Hiatella.

The occurrence of the alien species Anadara kagoshimensis is reported for the first time in the Ría de Arousa (Galicia, NW Spain) during 2013. Living specimens of this species have been recognized by morphological analysis. The cytochrome c oxidase subunit I gene has been partially sequenced and Maximum likelihood and Bayesian analyses carried out to confirm its identification. This new record reaffirms the presence of A. kagoshimensis, previously reported as Anadara inaequivalvis, along the Atlantic European coast extending the known distribution range in Spanish waters to the south.

The small-sized copepod community structure (<1  mm) and its response to environmental variability was examined during an annual cycle in Kalloni Gulf, a semi-enclosed coastal system in the NE Aegean Sea. Α 90 µm net was used in order to adequately sample the smaller copepod fractions. In the copepod ecology the spatial patterns dominated over the seasonal. Total copepod abundance increased towards the inner gulf area while diversity indices followed the opposite trend. The inner gulf copepod assemblage area was affected by the increasing magnitude of eutrophication, characterized by high abundance values, low species richness and dominance of a single species (e.g. Oithona nana). A clear seasonal succession of species was observed, ordered by temperature, salinity, chlorophyll a, heterotrophic bacterial biomass, organic and inorganic nutrients. Freshwater inputs and the subsequent nutrient inflow was a dominant phenomenon enhancing copepod production and negatively affecting the biodiversity of the assemblage. The great contribution of copepod larval stages in the total community and their year-round presence indicate the continuous production of copepods during the annual cycle, highlight the importance of the smaller size fraction and encourage the use of finer mesh-size nets when assessing the structure and dynamics of copepod communities.

This is the first study performed to determine the health status of the geoduck Panopea abbreviata in the San José and San Matías Gulfs (North Patagonia, Argentina). The study was based on 120 geoducks collected (30 specimens in each season) at Fracasso Beach (42°25′S 64°07′W) (San José Gulf) and 30 specimens collected during the austral summer at Puerto Lobos (42°00′S 65°05′W) (San Matías Gulf). The parasites found (prevalence in parentheses) were: prokaryotic inclusions (32.2%) were recorded in the epithelium of the digestive gland and gill filaments; ciliates (79%) mainly found in gills; Porospora-like gregarines (15.2%) in the connective tissue between inner and outer mantle epitheliums; the turbellarian Paravortex panopea (27.1%) in the intestine lumen; the nemertean Malacobdella arrokeana (98.3%) in the pallial cavity; and the green alga Coccomyxa parasitica (51%) parasitizing the haemocytes in the connective tissue of the distal end of the siphon. The highest mean parasitic abundance value was found in the late austral spring (November), coinciding with the lowest values of the condition index of the host. The populations of P. abbreviata from San José Gulf seemed to be devoid of severe pathogens.

The veined rapa whelk is one of the most important invasive species in the Black Sea ecosystem since the 1940s. Following its introduction to the Black Sea, it destroyed most of the bivalve populations, mainly the Mediterranean mussel and oysters. However, the veined rapa whelk has commercial importance for the Black Sea fisheries as an alternative product. In this study, we aimed to determine some population parameters of the veined rapa whelk based on indirect ageing through length–frequency data by using the Bhattacharya method. We collected 1704 specimens by dredging along the coasts of Samsun Province in the Central Black Sea in 2011 from June to November. The age of the population varied from 0 to 6. Von Bertalanffy growth parameters were estimated as L∞ = 112.35 mm, k = 0.310, t0 = −0.486 and W∞ = 243.94 g. Mean length and weight, length–weight relationship, mortality and exploitation rates were derived as L = 56.80 ± 0.36 mm, W = 45.67 ± 0.89 g, W = 0.0006 L2.719, Z = 0.96, M = 0.57, F = 0.39 and E = 0.40, respectively.

Crabs are thought to play a vital role in structuring gastropod populations. Studies quantifying the frequencies with which crabs attack gastropods in natural settings are, however, scarce. Although a wide variety of techniques exist with which predator–prey interactions can be investigated (e.g. laboratory experiments, exclusion caging, tethering and population surveys), there is a need for methods that can provide large amounts of quantitative data, particularly documenting the frequency with which crabs attack gastropods. This study examines the utility of using wax replicas of gastropods to determine crab attack frequencies. Replicas of Chlorostoma funebralis, Nucella ostrina and Nucella lamellosa were bolted to mesh screens and deployed in the rocky intertidal. Crabs attacked wax replicas of gastropods, leaving characteristic marks in the wax. In most cases, the appendage used in the attack could be identified from the marks (i.e. chelae vs walking legs). The effectiveness of this technique was verified using surveys of repair scar frequencies of the gastropod populations; patterns in attack frequency, determined from the number of marked wax replicas, were consistent with those of repair frequency, in that both were greater at the wave protected, quiet water locality. This study confirms the value of wax replicas in investigations of crab predation to determine the frequency and type of attack, and illustrates the potential of this method for quantifying predation intensity. The development of techniques that quantify the magnitude and exact nature of the effects of crab predation on intertidal communities is pivotal, given the intensity of commercial fishing of some species of crabs.

Knowledge of the population dynamics and productivity of exploited species is essential to achieve the sustainable development of fisheries, and to ensure sustainable, long-term use of these resources. The venerid clam Anomalocardia brasiliana is harvested as a fishery resource from the French West Indies to Brazil. Yet, the exploitation of this species is not backed by management or regulations based on scientific knowledge. This can result in reduced (or even depleted) A. brasiliana density and biomass. Here, we examined the population dynamics of A. brasiliana over the course of 1 year at Cidade Beach, a sheltered sandy beach located in south-eastern Brazil. Sampling was done monthly from March 2007 to February 2008. The sampled population was predominantly juvenile. Growth and recruitment were continuous, indicating no major fluctuation in limiting factors, such as temperature, salinity and food. Nevertheless, the abundance and the turnover rate (P/B ratio) of A. brasiliana at Cidade were much smaller than the values observed in other areas of occurrence. The mortality was more intense in young individuals, and the peak of individual production occurred in individuals with a 25 mm shell length, suggesting that individuals smaller than this size should not be exploited.