Flow cytometric DNA content analysis of neoplastic cells in haemolymph of the cockle Cerastoderma edule

Epizootiological outbreaks of disseminated neoplasia (DN) have been reported in association with mass mortalities in various bivalve species including the cockle Cerastoderma edule. A flow cytometric (FCM) procedure to study DNA content was successfully adapted and tested in haemolymph cells (haemocytes and neoplastic cells) of the cockle. The FCM results were similar to those obtained by histological analysis (DN diagnosis and haemolymph cell features). FCM analysis revealed differences in DNA content among normal haemocytes (diploid) and neoplastic cells. Four types of cells with abnormal DNA content were found in the haemolymph of affected animals: hypodiploid, hyperdiploid, triploid-sesploid and pentaploid. Our results suggest that the flow cytometric DNA content analysis can be applied to identify neoplastic cell types and to study the association between different cell types and the DN progression or remission in this edible and commercially important bivalve species.