Suchergebnisse

Globally, the Manila clam (Ruditapes philippinarum) stands as the second most important bivalve species in fisheries and aquaculture. Native to the Pacific coast of Asia, it is now well-established in North America and Europe, where its on-going management reflects local economic interests. The historic record of transfers spans the 20th century and suggests sequential movement from Japan to North America, as a hitch-hiker on oysters, and then intentional introduction in Europe, but global genetic data are missing. We have studied mitochondrial DNA and microsatellite markers in nine populations from Asia, North America and Europe. The results from the two types of markers indicated a good concordance of present-day genetic structure with the reported history of clam transfers across continents, and no evidence of relevant concealed introductions from continental Asia in Europe and North America. However, European populations showed a loss of genetic variability and significant genetic differentiation as compared to their American counterparts. Our study shows that in spite of the increasing ease for species to spread out of their native range, in the case of the Manila clam this has not resulted in new invasion waves in the two studied continents. ; This study was financed by grants AGL2007-60049/ACU and AGL2013-49144-C3-3-R from the Secretaría de Estado de Investigación (Spanish Government) to C. S. ; Peer reviewed

Comunicación presentada en el Aquaculture Europe 2014, celebrado en Donostia-San Sebastián, España, del 14 al 17 de octubre de 2014 ; The Manila clam is an Asian species that was introduced in Europe in the 1970's due to their advantageous characteristics for cultivation (Flassch and Leborgne, 1992). Currently, the Manila clam makes up the bulk of European production of clams (FAO data for 2012: 31 836 T). The species has spread over wide areas of the European coasts, either by natural reproduction, or aided by man through induced reproduction in hatcheries. A scientifically sound management of Manila clam genetic resources requires the knowledge of the genetic variability of European populations. Genetic studies (Sekine et al., 2006; Mao et al., 2011) indicate that the populations of the native range of the species in Asia are genetically subdivided, so the genetic composition of European populations would be dependent on the geographic area from which the founder stock came from. Published reports (Flassch and Leborgne 1992) claim that the first introduced clams were seeded in NW France and came from the NW Pacific coast, where, in turn, they were accidentally introduced 40 years earlier as a carry over with the seed of Pacific oyster (Crassostrea gigas) imported from Japan. Therefore, it is of great interest to know whether the clams currently living in the European coasts all come from the reported introduction of American/Japanese seed, or whether they are a mixed stock resulting from posterior, non reported introductions by clam farmers. With this aim we have conducted a genetic study of some European Manila clam populations, and compared them with samples taken form the natural range of the species in China and Japan, and from the American area of origin of the reported European founder stock. ; This work was supported by grant AGL2007-60049 from the National Research Plan of the Government of Spain. ; Peer Reviewed

Growth rate is one of the most important traits from the point of view of individual fitness and commercial production in mollusks, but its molecular and physiological basis is poorly known. We have studied differential gene expression related to differences in growth rate in adult individuals of the commercial marine clam Ruditapes decussatus. Gene expression in the gills and the digestive gland was analyzed in 5 fast-growing and five slow-growing animals by means of an oligonucleotide microarray containing 14,003 probes. A total of 356 differentially expressed genes (DEG) were found. We tested the hypothesis that differential expression might be concentrated at the growth control gene core (GCGC), i.e., the set of genes that underlie the molecular mechanisms of genetic control of tissue and organ growth and body size, as demonstrated in model organisms. The GCGC includes the genes coding for enzymes of the insulin/insulin-like growth factor signaling pathway (IIS), enzymes of four additional signaling pathways (Raf/Ras/Mapk, Jnk, TOR, and Hippo), and transcription factors acting at the end of those pathways. Only two out of 97 GCGC genes present in the microarray showed differential expression, indicating a very little contribution of GCGC genes to growth-related differential gene expression. Forty eight DEGs were shared by both organs, with gene ontology (GO) annotations corresponding to transcription regulation, RNA splicing, sugar metabolism, protein catabolism, immunity, defense against pathogens, and fatty acid biosynthesis. GO term enrichment tests indicated that genes related to growth regulation, development and morphogenesis, extracellular matrix proteins, and proteolysis were overrepresented in the gills. In the digestive gland overrepresented GO terms referred to gene expression control through chromatin rearrangement, RAS-related small GTPases, glucolysis, and energy metabolism. These analyses suggest a relevant role of, among others, some genes related to the IIS, such as the ParaHox gene Xlox, CCAR and the CCN family of secreted proteins, in the regulation of growth in bivalves ; This study was financed by grants AGL2010-16743 and AGL2013-49144-C3-3-R from the Dirección General de Investigación Científica y Técnica of the Spanish Government, and co-financed by COMPETE Program and by Portuguese National Funds through PEst-255 C/MAR/LA0015/2011 project and by the Portuguese FCT through UID/Multi/04326/2013 project. The stay of DC and CS in Faro in 2011 was funded by the transnational access program Assemble (Association of European Marine Biology Laboratories). The stays of CS in Padua in 2011 and 2016 were funded by a BEST 2011 fellowship from the Generalitat Valenciana and a fellowship from the Ministry of Education, Culture, and Sports of the Spanish Government, respectively ; Peer reviewed