Grooved Carpet Shell Clam Ruditapes Research Articles

Genetic structuring in the grooved carpet shell clam Ruditapes decussatus along the Moroccan coasts revealed by microsatellites

The grooved carpet shell clam Ruditapes decussatus is an economically important bivalve species in Morocco. Assessment of genetic diversity and genetic structure is essential for sustainable exploitation and effective management of this bivalve. Ten microsatellite loci were examined at seven localities along the Moroccan coast to determine the genetic diversity and population structure of the natural population of R. decussatus. A total of 280 clams were analyzed. The highest value of heterozygosity and mean number of alleles were found in the Mediterranean population (He: 0.685 and Na: 7.77), this can be considered in breeding and restocking programs. Five out of seven populations of R. decussatus showed signals of recent bottlenecks. Additionally, significant genetic differentiation among populations was detected (Fst =0.03125, p-val =1.021e−26). Bayesian analysis, neighbor-joining, and DAPC revealed the existence of two main groups spread on both sides of the 25th parallel. The AMOVA highlighted a genetic heterogeneity with the Southern and North group. These findings provide valuable information for efficient management and restocking based on aquaculture production for the Ruditapes decussatus inhabiting the Moroccan coasts.

Expression of four new ferritins from grooved carpet shell clam Ruditapes decussatus challenged with Perkinsus olseni and metals (Cd, Cu and Zn)

Iron has a fundamental role in life and in its biochemical reactions but, when in excess, it can promote the formation of free radicals which can lead to cell death. Therefore, managing the levels of iron is essential to regulate the production of oxidative stress related to iron, and ferritins are one of the main protein families involved in this process. Ferritins are ≈480 kDa multimeric proteins composed by 24 subunits, each with 19−26 kDa, which can accumulate up to 4500 iron atoms. Besides their role in managing iron bioavailability, they have also developed a role in organism immunity and defence present throughout evolution. In this work, we identified and characterized, for the first time, four different ferritin subunits in the clam Ruditapes decussatus, a bivalve commercially and ecologically important along the south Atlantic coast and in the Mediterranean basin, which is a major target of the parasitic protozoa Perkinsus olseni, considered one of the main causes of high levels of clam mortality. Following phylogenetic annotation, the four ferritins subunits identified were subdivided into two cytosolic and two secreted forms. All four subunits maintain the canonical ferritin structure with four main helices α (A–D) and a small helix (E), but the secreted ferritins present an additional helix in their N-terminal region (F), located after the signal peptide and with possible antimicrobial properties. Additionally, we identified in ferritin 4 an extra helix α (G) located between helices B and C. These alpha helix domains revealed high degree of similarity with antimicrobial peptides associated with antibacterial and antifungal activities. Analysis of the expression of these subunits showed that ferritins 1 and 2 are ubiquitously expressed while ferritins 3 and 4 are present mainly in visceral mass. Ferritin 1 lacked a putative functional iron response element (IRE) and appeared to be under a tight regulation. Ferritins 2 and 3 showed a strong response to infection by parasite Perkinsus olseni in contrast to ferritin 4, whose main response was related to exposure to a combination of metals. The synergistic effect between metals and infection promoted a general upregulation of the four ferritins. In conclusion, our results suggest that ferritins, besides their function in iron and metals detoxification, may play a determinant role in clam immune response.

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.

Does expansion of the introduced Manila clam Ruditapes philippinarum cause competitive displacement of the European native clam Ruditapes decussatus?

In several estuaries or lagoons of Europe the introduced Manila clam Ruditapes philippinarum has supplanted the native grooved carpet shell clam Ruditapes decussatus by occupying almost entirely its ecological niche and relegating it to restricted areas. However, it is not clear if the nonindigenous clam is the one directly responsible for these predominance patterns. Within this context, the main goal of the present study was to analyze the competitive interaction between the nonindigenous Manila clam and the native carpet shell clam to determine whether this interaction could impact directly growth and mortality of the native clam populations. The effect of exposure to predators on both species was also examined. For this purpose, between May 2010 and May 2011 a field experiment was conducted on an intertidal area in the Bay of Santander (N Spain) where both species coexist without an extreme predominance of the introduced species. Relative density of clam species was manipulated in a randomized block experimental design. The results obtained show that (i) the increased density of Manila clam simulating species expansion scenario does not affect growth or mortality of the native clam; and (ii) for densities of Manila clam substantially higher than observed in the field, predation plays an essential role in regulating both species populations, limiting their density increase. Moreover, Manila clam appears to be more negatively impacted by predation compared to the native clam. Overall, our results indicate that predation has a more significant effect on both populations when compared to competitive interaction.

MRNA-Seq and microarray development for the Grooved carpet shell clam, Ruditapes decussatus: a functional approach to unravel host -parasite interaction

BackgroundThe Grooved Carpet shell clam Ruditapes decussatus is the autochthonous European clam and the most appreciated from a gastronomic and economic point of view. The production is in decline due to several factors such as Perkinsiosis and habitat invasion and competition by the introduced exotic species, the manila clam Ruditapes philippinarum. After we sequenced R. decussatus transcriptome we have designed an oligo microarray capable of contributing to provide some clues on molecular response of the clam to Perkinsiosis.ResultsA database consisting of 41,119 unique transcripts was constructed, of which 12,479 (30.3%) were annotated by similarity. An oligo-DNA microarray platform was then designed and applied to profile gene expression in R. decussatus heavily infected by Perkinsus olseni. Functional annotation of differentially expressed genes between those two conditionswas performed by gene set enrichment analysis. As expected, microarrays unveil genes related with stress/infectious agents such as hydrolases, proteases and others. The extensive role of innate immune system was also analyzed and effect of parasitosis upon expression of important molecules such as lectins reviewed.ConclusionsThis study represents a first attempt to characterize Ruditapes decussatus transcriptome, an important marine resource for the European aquaculture. The trancriptome sequencing and consequent annotation will increase the available tools and resources for this specie, introducing the possibility of high throughput experiments such as microarrays analysis. In this specific case microarray approach was used to unveil some important aspects of host-parasite interaction between the Carpet shell clam and Perkinsus, two non-model species, highlighting some genes associated with this interaction. Ample information was obtained to identify biological processes significantly enriched among differentially expressed genes in Perkinsus infected versus non-infected gills. An overview on the genes related with the immune system on R. decussatus transcriptome is also reported.

Differential distribution pattern of native Ruditapes decussatus and introduced Ruditapes phillippinarum clam populations in the Bay of Santander (Gulf of Biscay): Considerations for fisheries management

The aim of the present study is to provide a first characterization of the grooved carpet shell clam Ruditapes decussatus (native) and the Manila clam Ruditapes phillippinarum (nonindigenous) populations in the Bay of Santander in order to improve the management of these commercially exploited resources. For this purpose a field survey was carried out in different fishing areas where samples were taken on transects, following artisanal shellfisher exploitation techniques. Biometric relationships, size frequency distributions, densities and stocks were evaluated for different fishing zones. In addition, a hydrodynamic model was applied in order to understand larval transport and recruitment patterns associated to the tidal currents and water flow. Within this context, the first evaluation of the clam populations in the Bay of Santander showed: (a) that fishing activity is performed on individuals under the minimum legal size (40 mm) and in closed areas, (b) a significant differences on density by zone (c) a distribution pattern with areas where both species coexist and areas where one of them dominates, (d) R. decussatus occurs at relatively low density in stations near the culture parks and (e) a limited recruitment in the inner parts of Cubas tidal fresh for R. phillippinarum and in the southern zones for R. decussatus. Based on this study, some managing guidelines are presented mainly focused on avoiding the overfishing of the native clam R. decussatus.

Study of perkinsosis in the grooved carpet shell clam Ruditapes decussatus in Galicia (NW Spain). III. The effects of Perkinsus olseni infection on clam reproduction

This study evaluated the effects of the protistan parasite Perkinsus olseni on the reproduction of the grooved carpet shell clam Ruditapes decussatus from Ria de Arousa, Galicia (NW Spain). Clams collected during a one-year period were processed by histology, and their histological sections were examined for gonadal stage, volume fraction of the gonadal components, and infection by P. olseni. R. decussatus had an annual cycle with four gonadal periods: rest (November–January), gametogenesis (February–March), ripeness (April–August) and reabsorption (September–October). The effects of the disease on the gonadal cycle occurred mainly during the gametogenesis and ripeness periods. P. olseni inhibited the gonadal development during the gametogenesis months, delaying the process until the ripeness period, and reduced the percentage of ripe individuals during the ripeness months. The inflammatory reaction caused by P. olseni infection affected the volume fraction (VF) of the gonadal components by increasing the VF occupied by hemocytes, and so reducing the VF of gametes, intrafollicular empty space, follicular walls, and connective tissue. However, no significant effect of infection on gonadal index, fecundity or spawning efficiency was obtained. Therefore, infected R. decussatus may recover from the delay of late gametogenesis, produce gametes and spawn without affecting spawning efficiency or fecundity.

Seasonal Variations in Gross Biochemical Composition, Percent Edibility, and Condition Index of the ClamRuditapes decussatusCultivated in the Ria Formosa (South Portugal)

The grooved carpet shell clam Ruditapes decussatus (L. 1758) is one of the most popular and profitable molluscs exploited in rearing plots in the Mediterranean. However, annual catch has been declining steadily since the early 1990s. To understand the seasonality of its nutritional value, thus providing an improved basis for economic valuation of the resource, gross biochemical composition, percent edibility, and condition index were investigated during a year with monthly periodicity in a commercially exploited population of the clam R. decussatus in the Ria Formosa, a temperate mesotidal coastal lagoon located in the south of Portugal. Our results show that total and nonprotein nitrogen covaried during the year, resulting in a protein content that peaked in the warmest months. Although complementary in summer, carbohydrate and lipid contents showed irregular annual trends. The observed seasonality was comparable with that shown by studies elsewhere at similar latitudes, and is underpinned by the reproductive cycle of the species. Our results show the clams to be at their prime nutritional value at the beginning of summer, when protein content peaks.