Cytomorphological characterization, classification and counting of haemocytes in freshwater crab, Varuna litterata (Crustacea: Decapoda)

Abstract

: Present study aims to characterize and classify the haemocyte structural types and to determine the total and differential haemocyte counts in freshwater crab, Varuna litterata . Haemolymph was collected from the crabs and subjected to the light microscopy, transmission electron microscopy, and flow cytometric analysis for the cytomorphological characterization and classification. Total and differential haemocyte counts were also carried out. On the basis of various cytomorphological features, haemocytes of V. litterata were classified into hyalinocytes, small granule haemocytes and large granule haemocytes. Hyalinocytes are round, oval, irregular, spindle or ellipsoid shaped cells with low to high nucleo-cytoplasmic ratio and contained a number of cytoplasmic organelles and a few minute-sized granules in the cytoplasm. Small granule haemocytes are large sized ovoid or ellipsoid shaped cells with a relatively high nucleo-cytoplasmic ratio and possessed numerous small sized granules. Large granule haemocytes are comparatively large-size, circular or ovoid shaped haemocytes with a high nucleo-cytoplasmic ratio and contained numerous large round refractile granules and a few small granules. Total haemocyte count of V. litterata is noted as 1.021 x10 6 to 3.108 x10 6 with a mean value of 2.145 ± 0.84 x 10 6 cells ml –1 . The relative percentages of hyalinocytes, small granule haemocytes and large granule haemocytes are accounted as 13.93, 55.24 and 30.83% respectively in the haemolymph. Outcome of this study might provide valuable information regarding the haemocyte profile of V. litterata that would be helpful to carry out further studies on haemocyte structural types to know about their specific functions and immune mechanisms.