Progressive development of circulating polyploid cells in Mytilus with hemic neoplasia

Abstract

The progressive development of hemic neoplasia in Mytilus is described using a flow cytometric method. Two experiments were conducted to determine the DNA content and evolution of the disease in individual Mytilus . In mussels with progressive hemic neoplasia, an increase in an apparently polyploid population occurred in conjunction with a decrease in the proportion of G sub(1a) cells. The formation of a second apparently polyploid population of circulating cells occurred and increased over time. The presence of these cell populations with these two ploidy levels represented a single population of autonomously replicating polyploid hemocytes in circulation. These polyploid circulating cell populations correspond to morphological changes in circulating cells which are described from hemocytological preparations. A second, rarer form of the disease, characterized by an increase of tetraploid neoplastic cells in circulation was observed. The 2 forms of the disease may represent alternative chromosomal lesions resulting from 2 alternative modes of integration of a foreign genome into the host genome. The significance of these findings on the observation of progression of the disease and on hypothetical etiologies is discussed.