COMPARATIVE-STUDY OF PHAGOCYTOSIS IN NORMAL AND DISEASED HEMOCYTES OF THE BIVALVE MOLLUSK MYA-ARENARIA

Large numbers of the soft-shelled clam Mya arenaria from New Bedford Harbor, Massachusetts, exhibit a blood cell disease referred to as hematopoietic neoplasia (HN). Diseased hemocytes differ morphologically from normal hemocytes by their high nucleocytoplasmic ratio. The phagocytic activity, one of the internal defense mechanisms, was compared in the two populations. Surface receptors, essential for recognition during phagocytosis, were demonstrated for both populations using Con A staining. Adherence and uptake were measured after in vitro incubation with yeast. Examination of hemocytes with scanning electron microscopy showed that yeast cells adhered only to the surface of normal hemocytes, and not to diseased hemocytes. Quantitative analysis of adherence and uptake of yeast by hemocytes showed that diseased hemocytes were unable to adhere and ingest yeast. This is thought to be caused by differences in cytoskeletal organization. Finally, the activity of four lysosomal enzymes was used to evaluate intracellular degradation in normal and diseased hemocytes. Histochemical analyses showed diseased hemocytes to have higher than normal acid phosphatase, nonspecific esterases and β-glucuronidase activity. These results indicate that enzyme activity cannot be directly correlated to intracellular degradation. However, it is possible that stress on the lysosomal system may activate certain enzymes. © 1992.