Clam Ruditapes Decussatus Research Articles

The Effect of Season on the Metabolic Profile of the European Clam Ruditapes decussatus as Studied by ¹H-NMR Spectroscopy.

In this study, the metabolome of Ruditapes decussatus, an economically and ecologically important marine bivalve species widely distributed in the Mediterranean region, was characterized by using proton Nuclear Magnetic Resonance (1H-NMR) spectroscopy. Significant seasonal variations in the content of carbohydrates and free amino acids were observed. The relative amounts of alanine and glycine were found to exhibit the same seasonal pattern as the temperature and salinity at the harvesting site. Several putative sex-specific biomarkers were also discovered. Substantial differences were found for alanine and glycine, whose relative amounts were higher in males, while acetoacetate, choline and phosphocholine were more abundant in female clams. These findings reveal novel insights into the baseline metabolism of the European clam and represent a step forward towards a comprehensive metabolic characterization of the species. Besides providing a holistic view on the prominent nutritional components, the characterization of the metabolome of this bivalve represents an important prerequisite for elucidating the underlying metabolic pathways behind the environment-organism interactions.

Uptake and metabolism of carbamazepine (CBZ) by clam Ruditapes decussatus and its effects in biochemical responses

1. Laboratory experiments were carried out to assess uptake and metabolism of the epilepsy drug, carbamazepine and its consequent biological responses in marine clam (Ruditapes decussatus) a model non-target organism in ecotoxicology.2. Clams were exposed to two nominal concentrations (C1 = 30 μg/L and C2 = 50 μg/L) of CBZ for a maximum period of 14 days. Analysis of CBZ and their metabolites in clam and water after exposure to two nominal concentrations of the pharmaceutical drug were performed using UPLC-HRMS analysis. CBZ accumulation reached an average tissue concentration of 1241.59 ng/g dw and 1664.33 ng/g dw at low and high nominal concentration, respectively.3. Furthermore, a metabolite (3-hydroxy-CBZ) was detected in tissues indicating carbamazepine translocation and metabolism inside clam, suspect screening of CBZ glucuronides was also performed by accurate mass extraction but it could not be detected.4. Activities of antioxidant enzymes superoxide dismutase, catalase and gluthatione-S-transferase generally increased. Change in the contents of glutathione, malondialdehyde and protein carbonyl were also studied.5. Results indicated that the bioaccumulation of CBZ resulted in the changes of the antioxidant defense system and the production of ROS with the oxidative stress, ultimately induced alteration in lipid peroxidation and protein carbonyl.

Combination of polycyclic aromatic hydrocarbons and temperature exposure: In vitro effects on immune response of European clam (Ruditapes decussatus)

Marine organisms are subjected to various biotic and abiotic factors such as changes of temperature and pollutants [e.g. polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and heavy metals, which may affect their defense mechanisms. In this context, the aim was to evaluate the combined effects of temperature (20 and 30 °C) and PAHs (fluorene, phenanthrene and pyrene) at two concentrations (10−5 and 10−3 mg mL−1) on the immune responses of the European clam Ruditapes decussatus were after 24 h of in vitro exposure. Total haemocyte count, cell viability, phenoloxidase, lysozyme, alkaline phosphatase, esterase, antibacterial and agglutinating activities were measured. Exposure to high temperatures resulted in lower phosphatase alkaline activity and higher haemocyte viability and antibacterial and haemagglutinating activities, compared with the values recorded for clams maintained at low temperature. Only pyrene induced a significant decrease in haemocyte lysozyme (at 20 and 30 °C) and esterase (at 30 °C) activities. The total haemocyte count was increased by phenanthrene and pyrene at 20 °C and at 30 °C, respectively. Alkaline phosphatase activity increased when haemocytes were exposed to pyrene at 30 °C but decreased in the presence of fluorene at 20 °C. Furthermore, haemocyte viability was low in the presence of pyrene and fluorene at 20 °C and 30 °C, respectively, but was unaffected by phenanthrene. Antibacterial activity was significantly increased and no-significantly affected by the presence of pyrene and fluorene at 20 °C and 30 °C, respectively. The present study demonstrates the strong effect of PAHs and high temperature on haemocyte viability and other important immune functions, including phosphatase alkaline and antibacterial activities. Furthermore, changes in the immune parameters of European clam resulting from high temperatures may modulate the effects of PAHs and vice versa.

Toxicity assessment of ZnO-decorated Au nanoparticles in the Mediterranean clam Ruditapes decussatus

The synthesis of hybrid nanomaterials has greatly increased in recent years due to their special physical and chemical properties. However, information regarding the environmental toxicity associated with these chemicals is limited, in particular in the aquatic environment. In the present study, an experiment was performed in which the marine bivalve (Ruditapes decussatus) was exposed for 14days to 2 concentrations of zinc oxide-decorated Au nanoparticles (Au-ZnONPs: Au-ZnONP50=50μg/L; Au-ZnONP100=100μg/L).The stability and resistance of Au-ZnONPs in the natural seawater were assessed by combining transmission electron microscopy and dynamic light scattering. Inductively coupled plasma-atomic emission spectroscopy revealed uptake of these nanoparticles within clams and their ability to induce metallic deregulation. The results obtained indicate that Au-ZnONPs induce biochemical and histological alterations within either the digestive gland or gill tissues at high concentration. This was deduced from the significant increase in H2O2 level, superoxide dismutase and catalase activities and malondialdehyde content. Furthermore, the toxicity of Au-ZnO nanoparticles was linked with the increase of intracellular iron and calcium levels in both tissues. Histological alterations in gill and digestive gland were more pronounced with Au-ZnONP100 and this is likely related to oxidative mechanisms. Gill and digestive gland are differentially sensitive to Au-ZnONPs if the exposure concentration is higher than 50μg/L.In conclusion, the parameters considered here could constitute reliable biomarkers for evaluation of hybrid nanoparticles toxicity in environmental model organisms. In addition, based on the results obtained, gill and digestive gland of R. decussatus could be proposed as models to detect harmful effects of hybrid nanoparticles.

Mortality event involving larvae of the carpet shell clam Ruditapes decussatus in a hatchery: isolation of the pathogen Vibrio tubiashii subsp. europaeus.

Diseases caused by bacteria belonging to the genus Vibrio are a common, as yet unresolved, cause of mortality in shellfish hatcheries. In this study, we report the results of routine microbiological monitoring of larval cultures of the carpet shell clam Ruditapes decussatus in a hatchery in Galicia (NW Spain). Previous episodes of mortality with signs similar to those of vibriosis affecting other species in the installation indicated the possibility of bacterial infection and led to division of the culture at the early D-veliger larval stage. One batch was cultured under routine conditions, and the other was experimentally treated with antibiotic (chloramphenicol). Differences in larval survival were assessed, and culturable bacterial population in clams and sea water was evaluated, with particular attention given to vibrios. Severe mortalities were recorded from the first stages of culture onwards. The pathogen Vibrio tubiashii subsp. europaeus was detected in both batches, mainly associated with larvae. Moreover, initial detection of the pathogen in the eggs suggested the vertical transmission from broodstock as a possible source. Experimental use of antibiotic reduced the presence and diversity of vibrios in sea water, but proved inefficient in controlling vibrios associated with larvae from early stages and it did not stop mortalities.

The Limpets and Winkles’ Enigma. Premier aperçu sur la malacofaune marine des occupations mésolithiques et néolithiques de la colline Saint-Charles à Marseille (VIIIe millénaire-IVe millénaire av. J.-C.)

La colline Saint-Charles à Marseille a fait l’objet d’opérations d’archéologie préventive de 2000 à 2008 au préalable à une réhabilitation immobilière. Les sondages préliminaires ont montré qu’elle était partiellement occupée durant le Mésolithique I et le Néolithique ancien (VIIIe et VIe millénaires av. J.-C) et probablement entièrement durant le Néolithique moyen et récent (IVe millénaire av. J.-C.). Toutefois, seuls quatre «sites préhistoriques » définis artificiellement par l’emprise des opérations immobilières et pour lesquels les niveaux stratigraphiques étaient bien conservés ont fait l’objet de fouilles. Des structures d’habitat de différentes natures (trous de poteaux, fosses, sols de circulation, plan d’habitat, murs en terre) et du matériel archéologique (lithique, céramique) sur l’ensemble des sites témoignent des occupations successives de cette portion de colline. L’une des caractéristiques majeures de ces habitats et l’objet de cet article est la présence de malacofaune marine dans tous les niveaux archéologiques de la colline à l’exclusion de tous autres vestiges de faune terrestre sauvage ou domestique et de restes végétaux sauvages ou cultivés. L’étude permet d’avancer quelques hypothèses sur les raisons de cette présence exclusive. Elle met en évidence une évolution sur le long terme des espèces en présence. Aux patelles (Patella sp.) et bigorneaux (Phorcus turbinatus) consommés au Mésolithique I, succèdent les coques (Cerastoderma sp.) et les bigorneaux (Phorcus turbinatus) au Néolithique ancien, puis les cérithes (Cerithium vulgatum) et les bigorneaux (Phorcus turbinatus) au Néolithique moyen et enfin les murex (Hexaplex trunculus) et les tritons (Charonia lampas et variegata) au Néolithique moyen-récent. Le choix des espèces et du biotope apparaît orienté pour chaque période et permet de supposer des options préférentielles de cueillette en relation avec une évolution du goût et des techniques de collecte tout au long de l’occupation de la colline. Au Mésolithique et au Néolithique, la faible proportion de coquilles et leur dispersion au sol sur le site de Bernard-du-Bois ne conduisent pas à privilégier l’hypothèse d’un amas coquillier, mais plutôt celui d’un dépôt coquillier. La cueillette de la malacofaune marine du Mésolithique I et du Néolithique ancien semble intégrée de façon opportuniste aux stratégies d’exploitation du territoire et pourrait être rapportée sur la colline à la faveur de déplacements saisonniers en complément d’un autre type de diète alimentaire. Au Néolithique moyen et récent, il s’agit toujours d’un dépôt coquillier. Toutefois, les stratégies de collecte s’orientent vers des coquillages à plus fort rendement alimentaire dont la consommation pourrait compenser en partie une diète carnée d’origine terrestre. Par ailleurs, à partir du Néolithique moyen, sous les effets de la remontée de la mer, la colline passe d’un statut de site «d’arrière-pays » à celui de site côtier. La fréquentation de la colline devient plus pérenne. Durant le Mésolithique I et le Néolithique ancien, la présence de malacofaune marine sur les sites du littoral et sur la colline laisse supposer des liens de complémentarité, internes au bassin de Marseille. Au Néolithique moyen, la colline est intégrée aux réseaux de circulation de matières premières lithiques qui prennent place en dehors du bassin de Marseille (silex bédoulien, roches vertes), mais la nature des contreparties échangées demeure inconnue. Les stratégies économiques mises en place par les groupes humains du Mésolithique et du Néolithique méridional pour la gestion de l’environnement côtier en relation avec les sites de l’arrière-pays au moment du passage à l’Holocène apparaissent variées.

Vibrio barjaei sp. nov., a new species of the Mediterranei clade isolated in a shellfish hatchery

Seven isolates were obtained from different culture stages of carpet shell clam (Ruditapes decussatus) reared in a bivalve hatchery (Galicia, NW Spain). Three groups were differentiated by genotyping techniques and phenotypic profiles and representative trains were selected to further taxonomic studies. These strains were studied by a polyphasic approach and in basis of the phylogenetic analysis based on concatenated sequences of the five housekeeping genes ftsZ, gyrB, pyrH, recA and rpoA formed a tight group into the Mediterranei clade of the genus Vibrio. Percentages of genomic resemblance, including average nucleotide identity, in silico genome-to-genome comparison and wet DNA–DNA hybridization between the type strain and the closest relatives Vibrio mediterranei and Vibrio thalassae were below of the proposed boundaries for the definition of species. The novel isolates could be also differentiated from the related taxa on the basis of several phenotypic traits and fatty acid profiles. Results obtained support the description of a novel species into the Mediterranei clade, for which the name Vibrio barjaei sp. nov. is proposed, with strain 3062T (=CECT 9090T=CAIM 1921TT=LMG 29358T) as the type strain.

Impacts of rearing techniques on growth, survival and bacterial microbiota of carpet shell clam (Ruditapes decussatus) larvae

In this study, we investigate the impacts of two water treatment regimes, the closed aquaculture system (CAS) and flow-through system (FTS), on the carpet shell clam (Ruditapes decussatus) larval microbiota, growth and survival. A bacteriological barrier (B) was created among breeder stage treated by florfenicol (FF, 8 mg L−1day−1 per 5 days). After spawning, larvae were maintained in five different rearing techniques: CAS; FTS; B + CAS; B + FTS and B + CAS + FF (8 mg L−1 day−1 per 3 days). Significant decrease was observed in both total bacterial count and presumptive Vibrio count (PVC) in FF-treated breeders. Besides, larvae reared in B + FTS showed significantly lower PVC than larvae maintained in other rearing techniques. It was also determined that growth and survival of larvae reared in B + CAS + FF and B + FTS were significantly better than those reared in other systems. One hundred and twelve Vibrio strains, isolated from breeders, eggs and larvae, were subjected to some bacteriological tests (API 20E strips, vibriostatic agent O/129, growth at different temperatures and salinity). Vibrio alginolyticus was the predominant isolated species (36.61 %), followed by V. fluvialis (25 %), V. vunificus (17.86 %), V. cholera (13.39 %) and V. paraheamolyticus (7.14 %). These results may contribute to the understanding of the effect of rearing techniques on the bacterial load, survival and growth of early life stages of R. decussatus larvae.

Effects of an invasive mussel, Arcuatula senhousia, on local benthic consumers: a laboratory 13C‐labeling study

Filter-feeding bivalves play an important ecological role in aquatic systems through benthic–pelagic coupling. However, the mechanisms by which invasive mussels influence the food uptake by local consumers are little known. We tested the interactive effects of the invasive mussel Arcuatulasenhousia and the native clam Ruditapes decussatus on the uptake of 13C-enriched microalgae, Isochrysis sp., by two polychaetes, the surface deposit feeder Cirriformia tentaculata and the sub-surface deposit feeder Phylo foetida. Polychaetes were exposed to two different densities of A.senhousia and R. decussatus used alone or together. In each treatment, the 13C-concentration throughout the sediment horizon (0–0.5, 0.5–2.5 and 2.5–5 cm) was also quantified. Results showed that, irrespective of bivalve densities, the 13C-uptake by C. tentaculata was lower in the presence of the two bivalves together than in the presence of one bivalve species (either A. senhousia or R. decussatus). This was consistent with decreased 13C-concentrations in the 0–0.5 cm sediment layer in the treatment with the two bivalves together. Contrary to C. tentaculata, no changes were observed among treatments in the 13C-uptake by P. foetida. This possibly reflected a limited 13C-enrichment of the lower sediment layers. Our main findings are: (1) A.senhousia reduces the 13C-uptake by R. decussatus, and (2) A.senhousia reduces the availability of phytoplankton-derived C for deposit feeders by impairing the feeding, incorporation and bio-deposition of R. decussatus. We conclude that the interaction of A.senhousia with native bivalves needs to be taken into consideration in future food web studies.

Response of the carpet shell clam (Ruditapes decussatus) and the Manila clam (Ruditapes philippinarum) to salinity stress

AbstractEnvironmental stressors are known to play an important role in determining the distribution and abundance of intertidal species. Marine molluscs are particularly susceptible to changes in water temperature and salinity in inter-tidal zones.

Assessing the geographic scale of genetic population management with microsatellites and introns in the clam Ruditapes decussatus.

The clam Ruditapes decussatus is commercially important in southwestern Europe, suffering from population decline and hybridization with exotic Manila clam (R. philippinarum). Previous studies with intronic markers showed a genetic subdivision of the species in three races (Atlantic, West Mediterranean, and Adriatic‐Aegean). However, detailed population genetic studies to help management of the main production areas in the southwest of Europe are missing. We have analyzed eight Atlantic and two Mediterranean populations from the Spanish coasts using 14 microsatellites and six intronic markers. Microsatellites confirmed the Atlantic and West Mediterranean races detected with introns and showed that genetic variability was higher in Mediterranean than in Atlantic populations. Both marker types showed that genetic differentiation of Atlantic populations was low and indicated that populations could be managed at the regional level in the case of Cantabrian and Gulf of Cadiz areas, but not in the case of Rias Baixas and the Mediterranean. This study shows the interest of including different types of markers in studies of genetic population structure of marine organisms.

Beneficial effects of carpet shell clam (Ruditapes decussatus) depuration during short periods of conditioning in shellfish hatchery: Role of the temperature and phytoplankton on reduction and diversity of vibrios

Broodstock conditioning in hatcheries is the step previous to spawning and its optimization may be a key to the success of larval cultures. Cleaning and brushing of the broodstock and the utilization of antibiotics to reduce their vibrios load are used regularly as routine prophylactic measures prior to spawning induction. The development of protocols to reduce these bacteria using cheap and harmless techniques is of utmost importance for commercial bivalve production in hatcheries. With this aim, we have evaluated initially different conditionings (A–D) during short periods (a total of four weeks): first two weeks under gradient temperature (increasing +0.3°Cday−1 from 14.5°C to 20°C), without (A) or with phytoplankton (B), and constant temperature (20°C) without (C) or with phytoplankton (D). Afterwards, all conditionings were kept at 20°C and fed for two more weeks. Furthermore, broodstock optimal feeding time was re-evaluated during a second trial series. In all conditionings, bacterial loads were determined in terms of marine heterotrophic bacteria (MHB) and presumptive vibrios (PV). Broodstock under the optimal short period of conditioning (conditioning C) obtained the best gonadal development and a significant reduction in PV load at a lower expense. A total of 61 PV were isolated from all conditionings and identified by sequencing the 16S rRNA gene. Splendidus clade was dominant in the samples coming from natural beds. Diversity of vibrios changed throughout the conditionings in the hatchery favoured by exogenous factors whose effect was mainly observed at the end of the trials: Splendidus clade was also dominant in the broodstock conditioned at gradient temperature and Mediterranei and Harveyi clades were prevalent at constant temperature. Moreover, the percentage of transformation to D-larvae was estimated and the vertical transmission of vibrios from broodstock to eggs and D-larvae was suggested. Implementation of conditioning C reduces considerably the Vibrio load of clams without using antibiotics, and thus it represents a novel, cheap, environmental friendly and harmless methodology that can be easily transferred to commercial hatchery. Statement of relevanceRoutine prophylactic measures for bivalve broodstock arriving hatchery facilities include its cleaning/brushing and the frequent use of antibiotics to reduce its bacterial load, particularly Vibrio, as step previous to spawning induction. The depuration protocol proposed reduces significantly Vibrio load without using antibiotics and represents a novel, cheap, environmental friendly and harmless methodology that can be easily transferred to commercial hatcheries.

Recirculation nursery systems for bivalves

In order to increase production of bivalves in hatcheries and nurseries, the development of new technology and its integration into commercial bivalve hatcheries is important. Recirculation aquaculture systems (RASs) have several advantages: high densities of the species can be cultured resulting in a cost-effective production system; optimal temperature maximizes production and allows rapid turnover of the product; stable water quality improves growth rate and minimizes stress and potential loss by diseases. Pilot RAS systems were developed for seed rearing of oysters (Crassostrea gigas), scallops (Pecten maximus), mussels (Mytilus edulis) and clams (Ruditapes decussatus). Optimal feed addition and waste matrix were determined. Based on this, system flow rates were designed. Seed growth in the pilot RAS systems was compared at different renewal rates and with growth in flow-through systems (FTS). All four species can be reared in RAS and showed similar growth in RAS and in FTS or in RAS with a higher renewal rate. RAS can keep O2, nitrogen and pH within the desired range. Temperature was generally higher in RAS than in FTS, probably due to heat induced by the pump circulating the water. The supply of sufficient amount of food in combination with a desire to reduce the renewal rate calls for use of concentrated feed in RAS.

Combined effects of metal contamination and abiotic parameters on biomarker responses in clam Ruditapes decussatus gills: an integrated approach in biomonitoring of Tunis lagoon.

The spatial and seasonal alteration in a battery of biomarkers responses (enzymatic activity of glutathione-S-transferase, catalase and acetylcholinesterase and lipid peroxidation) were investigated to assess the metal derived effects in clam (Ruditapes decussatus) gills, collected from Tunis lagoon (Tunisia). Trace metals (Ag, As, Cd, Cu, Hg, Mn, Ni, Pb, V and Zn) concentrations were assessed seasonally in sediments and tissues of R. decussatus from three different sites (S1, S2 and S3). Bioaccumulation factor (BAF) analysis showed a spatio-temporal variation of metal uptake rates in clams through sediments. Likewise, the multibiomarker approach enabled a time-site trend differentiation between sites with distinctive degrees of anthropogenic contamination. Site S2 was identified as the most impacted region due to the presence of different contamination sources (shipping and industrial activities). The results suggest that biomarker's seasonal variation arises from a complex interaction between environmental conditions (e.g. temperature, salinity) and probably biological factors (mainly the reproduction process) along with anthropogenic pressure. The general biological response measured with the IBR index at all the sampling sites revealed the highest metabolic stress in summer. The combined effects of metal contamination and increased temperature and salinity in summer appear to induce the highest metabolic adaptation response. The selected biomarkers provided an integrated response, which is useful for the assessment of the combined effects of metal contamination and abiotic parameters in clams and the environmental status of coastal lagoon ecosystem.

Vibrio bivalvicida sp. nov., a novel larval pathogen for bivalve molluscs reared in a hatchery

Three isolates were obtained from cultures of carpet shell clam (Ruditapes decussatus) reared in a bivalve hatchery (Galicia, NW Spain) from different sources: healthy broodstock, moribund larvae and the seawater corresponding to the larval tank. All isolates were studied by a polyphasic approach, including a phylogenetic analysis based on concatenated sequences of the five housekeeping genes ftsZ, gyrB, pyrH, recA and rpoA. The analysis supported their inclusion in the Orientalis clade of the genus Vibrio, and they formed a tight group separated from the closest relatives: Vibrio tubiashii subsp. europaensis, Vibrio tubiashii subsp. tubiashii and Vibrio orientalis. The percentages of genomic resemblance, including average nucleotide identity, DNA–DNA hybridization and in silico genome-to-genome comparison, between the type strain and the closest relatives were below values for species delineation and confirmed the taxonomic position of the new species, which could be differentiated from the related taxa on the basis of several phenotypic and chemotaxonomic features, including FAME and MALDI-TOF-MS. The pathogenicity of the new species was demonstrated in larvae of R. decussatus, Ruditapes philippinarum, Ostrea edulis and Donax trunculus. The results demonstrated that the strains analyzed represented a novel species in the Orientalis clade of the genus Vibrio, for which the name Vibrio bivalvicida sp. nov. is proposed, with 605T (= CECT 8855T=CAIM 1904T) designated as the type strain.

The endocrine-disrupting effect and other physiological responses of municipal effluent on the clam Ruditapes decussatus.

In order to document the potential endocrine disrupting and toxic effect of the municipal wastewater effluents discharged into the Sfax coastal area (South of Tunisia), specimens of clam R. decussatus were collected from a reference site and were in vivo exposed to treated sewage effluent for 30 days. To this end, estrogenic and androgenic activities were measured in the gills to assess potential accumulation and regulation of active compounds. After effluent exposure androgenic activity in organic extracts increased up to fivefold compared to controls and remained elevated, while estrogenic activity was not significantly affected by exposure. As a consequence, remarkable disruptions in the gametogenesis activity, glycogen content, and Vitellogenin-like protein levels in male clams were observed. A parallel analysis of heavy metals in clam tissues was determined. A significant uptake of Ni, Zn, and Pb in soft tissues of exposed clams was observed. The significant increase of malondialdehyde (MDA) concentrations as a function of exposure time implies that clams have been exposed to an oxidative stress probably due to the presence of high metal concentrations in sewage effluent. Correlation analysis has revealed a statistically significant and positive relationship between MDA levels and metal concentrations in clams' tissues. The acetylcholinesterase activity was not significantly affected by exposure. Altogether, these results showed that a short-term exposure to a mixture of chemical compounds released by the Sfax wastewater treatment plant induce adverse physiological and reproductive effects in R. decussatus. Further studies are underway in order to evaluate its long-term impacts on aquatic wildlife in the gulf of Gabes area.

Effects of clam rake harvesting on the intertidal Ruditapes habitat of the English Channel

Abstract Recreational and professional clam fishing was an important activity on the extensive intertidal zone of the western Cotentin coast (western English Channel). A variety of fishing gear was used to harvest the target species: the European clam Ruditapes decussatus (Linnaeus, 1758) and the introduced Manila clam R. philippinarum (Adams and Reeve, 1850). In this study, we studied the effect of rake harvesting during the spring tides of February–March 2014, following an experimental design with a control station and three stations impacted by rake harvesting in three sediment types: sandy, gravelly, and mixed gravelly rocky habitats. No significant sediment and macrofauna changes occurred at the three sites after rake harvesting. Nevertheless, the number of clams decreased significantly after raking on the gravelly habitat, whereas in the other two habitats, sediment transport in this high-energy hydrodynamic environment was able to transfer clams and other macrofauna species across the fishing sites, thus minimizing the effects of rake harvesting. Therefore, although the effect of rake harvesting appeared limited during winter, the regional impact (high fishing pressure along 60 km of coast) and increase of recreational fishers during summer needed to be studied in the future.

Comparison of Gametogenic Cycles of the Endemic European Carpet Shell Clam (Ruditapes decussatus) and the Introduced Manila Clam (Ruditapes philippinarum) from a Temperate Coastal Mediterranean Lagoon in the Dardanelles, Turkey

In this study, the gametogenic cycle of the newly introducedManila clam Ruditapes philippinarum was described for the first time for Turkish waters and compared with that of the native European grooved carpet shell clam Ruditapes decussatus coexisting in Çardak Lagoon (Çanakkale, Turkey) in the Dardanelles. A total of 480 individuals were sampled for each species between January andDecember 2011. Both species exhibited similar distinct seasonal changes in gonad activity and completed their gametogenic cycles. In both species, gonads advanced very fast after winter reaching ripe stage in April and May in theManila clams and carpet shell clams, respectively. In Manila clams, spawning commenced in April and continued until October. In carpet shell clams, spawning started in May, but the main spawning event occurred in June and continued until July with a discontinuation in August and a marginal spawning taking place in September and possibly in October. Gonad index (GI) values were indicated similarities in gonad development between males and females of both species with apparent synchronism between sexes during early development, first maturation and early spawning until July. We report for the first time the reproduction of the Manila clam in Turkish waters and show that optimal conditions for gametogenesis and spawning exist for this exotic species from March until October in the Dardanelles. This information will be useful for clam fishery management especially in areas where carpet shell clam and the Manila clam are known to coexist.

Perkinsosis in the clams Ruditapes decussatus and R. philippinarum in the Northeastern Atlantic and Mediterranean Sea: A review

Perkinsosis is a disease of gastropod and bivalve molluscs caused by protozoan parasites of the Perkinsus genus. These parasites have been responsible for mass mortalities worldwide, with a significant impact in both fisheries and aquaculture, and resulting in severe economic losses. This review focuses mainly on current knowledge of diagnostic methods and on the distribution of Perkinsus spp. in the Northeastern Atlantic and Mediterranean Sea, which infect the grooved carpet shell clam Ruditapes decussatus and the Japanese carpet shell clam Ruditapes philippinarum. The association between perkinsosis and high mortality rates of R. decussatus and R. philippinarum in southern European countries such as Portugal and Italy is discussed as is the role of environmental factors in those mortality outbreaks. The putative introduction of Perkinsus olseni into the Northeastern Atlantic and Mediterranean Sea is also discussed, as are management strategies that could be used to mitigate the impact of perkinsosis in production of R. decussatus and R. philippinarum.

Effects of 2-(4-Methoxyphenyl)-5, 6-trimethylene-4H-1, 3, 2-oxathiaphosphorine-2-sulfide on biomarkers of Mediterranean clams Ruditapes decussatus

The effects of exposure to a novel synthetic organophosphorus compound, 2-(4-Methoxyphenyl)-5, 6-trimethylene-4H-1, 3, 2-oxathiaphosphorine-2-sulfide (OMTOS) concentrations (Control=0, C1=0.01, C2=0.1, C3=1 and C4=10μg/L) were investigated in the clam Ruditapes decussatus. Vitellogenin (Vg)-like protein levels in haemolymph from males and females were investigated. Concentrations of 1μg/L and 10μg/L significantly decreased Vg levels in male haemolymph after 7 days, whereas significant variations were only found in females treated with 10μg/L. On the other hand, superoxide dismutase (SOD), catalase (CAT) and acetylcholinesterase activities (AChE) in whole soft tissue were measured after 2, 4 and 7 days of exposure to the same series of concentrations. After 2 days of exposure, 0.1, 1, and 10μg/L of OMTOS increased SOD activity significantly, but this decreased with 10μg/L after 4 and 7 days. No changes in CAT activity were observed after 2 days compared to controls. OMTOS significantly reduced AChE activity after 4 and 7 days in treated clams with the highest concentration 10μg/L, but it did not induce significant variations at the other concentrations tested. Our study demonstrates that OMTOS alters biochemical parameters in R. decussatus, even at low concentrations, and suggests differing modes of action of the contaminant. Using clams is a powerful tool to provide valuable insights into possible mechanisms of environmental toxicity of novel synthetic organic products both in non-target organisms and the marine ecosystem. Additionally, our results highlight that biomarker responses facilitate elucidation of putative mechanisms of action of OMTOS in non-target species.