On the ultrastructure and classification of hemocytes of freshwater crab Cylindrothelphusa steniops (Crustacea: Decapoda)

Abstract

The present study employs light and electron microscopy methods to elucidate the morphological and ultrastructural details of hemocyte profile of the freshwater crab Cylindrotelphusa steniops. Hemocytes were classified based on the cell shape, nucleus characteristics, appearance of cytoplasmic organelles, pseudopodia, presence and nature of granules. We identified four cell types which include agranulocyte (Ag), granulocyte I (GI), granulocyte II (GII), and semigranulocytes (SGC). Agranulocytes were oval or irregular shaped cells, devoid of granules in their cytoplasm. They had prominent pseudopodia and phagosome-like structures in the cytoplasm, suggesting a phagocytic function. Granulocytes I are usually round to oval and rich in cytoplasmic organelles like RER, mitochondria, ribosomes, multifarious granules and small vesicles, pointing towards synthetic and secretory functions. Granulocytes II are elongated or oval, cytoplasm contained organelles like mitochondria, RER, ribosomes, vacuoles, Golgi bodies with inflated cisternae and distinctly large, dense granules. Semigranulocytes are round to oval cells with ribosomes, vacuoles, RER cisternae, mitochondria and small dense granules throughout the cytoplasm. Moreover, SGC with a large vacuole and endocytosed materials were observed, probably involved in endocytosis of foreign materials. We propose that the information generated from the present study will be useful for the aquacultural practises of freshwater decapod crustaceans.