A histopathological survey of some commercially exploited bivalve molluscs in northern Patagonia, Argentina

A survey of pathological conditions affecting natural beds of the most economically important bivalve species was performed for first time in the Argentinean Sea. The bivalves studied were Aequipecten tehuelchus (Pectinidae), Mytilus edulis, Aulacomya atra (Mytilidae), Protothaca (=Venus) antiqua (Veneridae), Ostrea puelchana (Ostreidae) and Pododesmus rudis (Anomiidae), all from San José gulf (42°20′S, 64°20′W), in northern Patagonia, Southwest Atlantic Ocean. Samples of about 30 adult individuals from each molluscan species were collected and processed by standard histological techniques. Rickettsia-like organisms were the commonest parasites found, followed by ciliates, Nematopsis-like spores, sporocysts and metacercariae of Trematoda, larval Cestoda, Turbellaria and two crustaceans (an isopod and a pea crab). A protozoan of uncertain taxonomic affinities, similar to that formerly reported as Perkinsus karlssoni in Argopecten irradians, was found in A. tehuelchus. DNA analysis demonstrated that it does not belong to a Perkinsus species. The commercially exploited bivalves here studied seem to be devoid of serious pathogens. None of the parasites appear to be a problem to future farming due either to low infestation levels or low pathological effect. Moreover, none of these parasites is OIE notifiable, although to confirm these initial results it is necessary to perform a more exhaustive survey in several beds from different seasons. In order to manage Argentinean stocks, a continuous, organized survey, satisfying international standards, is strongly recommended.