Morphological and cytochemical studies of peripheral blood cells of Schizothorax prenanti

The morphological and cytochemical studies of peripheral blood cells of Schizothorax prenanti were studied by light and electron microscopy. Erythrocytes, thrombocytes and three types of leucocytes, lymphocytes, neutrophils and monocytes, were distinguished and characterized. In addition to mature erythrocytes, immature and dividing erythrocytes were observed. A few organelles such as mitochondria were distributed in the cytoplasm of erythrocytes. Lymphocytes with heavily clumped heterochromatic nucleus and minimal cytoplasm were classified into small and large lymphocytes. Three different populations of granules, with distinctive ultrastructural aspect, were observed in neutrophils. Monocytes were the fewest leucocytes possessing rich organelles, phagocytized materials and vacuoles. Thrombocytes with various types were the most abundant blood cells among leucocytes and contained a prominent nucleus with dense bands of heterochromatin and many cytoplasmic vacuoles. Periodic acid-Schiff staining was positive in neutrophils, monocytes, lymphocytes and thrombocytes, but not in erythrocytes. Peroxidase-positive staining was observed in neutrophils and monocytes, but not in erythrocytes, lymphocytes and thrombocytes. Only neutrophils were positive for oil red O. Except for erythrocytes, the other blood cells stained positively for acid phosphatase. Only neutrophils and monocytes were positive for α-naphthyl acetate esterase. None of the cells studied were positive for alkaline phosphatase. The morphologic and cytochemical features of blood cells of S. prenanti are similar to those of other fish. This investigation may be helpful as a tool to monitor the health status of cultured S. prenanti and will grant early detection of clinical pathology.