Gill tissue pathogenicity and hemocyte behavior in the crab paratelphusa hydrodromous exposed to lead chloride

Abstract

Different size groups of Paratelphusa hydrodromous were exposed to sublethal concentrations of 0.2–1.0 mg/L lead chloride solution for 60 days to study the hemogram responses in relation to gill pathogenic changes. The induction of hemocytopenia was a dose‐dependent and time‐related phenomenon. Adult male crabs showed some tolerance to inorganic lead. In granulocytes, long‐term stress provoked intense granulation of the cytoplasm and hypertrophy of the nucleus. The presence of hemocyte infiltrate in gills was a characteristic sign of early inflammatory lesion. Random migration, encapsulation and hemocytosis were seen near the necrosed foci of gills. There were histological evidences in support that intravascular hemolymph clotting was initiated by lysed hyaline hemocytes. The release of filamentous material by the lysed hyaline hemocyte was recognized as an apparent attempt to seal off the hemorrhagic lesion. The granulocyte proliferation was usually indicative of chronic toxicosis and the absence of blood clots was considered to be a stage before the occurrence of mortality. Adherence, agglutination and lysis of hemocytes may have reduced the number of circulating free hemocytes in toxified crabs.