MICROSCOPIC STRUCTURE AND CYTOCHEMICAL CHARACTERISTICS OF PERIPHERAL BLOOD CELLS IN MEGALOBRAMA AMBLYCEPHALA

The microscopic structure and cytochemical characteristics of peripheral blood cells in Megalobrama amblycephala were observed by routine Wright staining and cytochemical staining. Six types of cells were distinguished in the peripheral blood cells in Megalobrama amblycephala: erythrocytes, lymphocytes, monocytes, neutrophils, eosinophils and thrombocytes. The lymphocytes are the most abundant blood cells except erythrocytes, followed by thrombocytes, monocytes, neutrophils and eosinophils. The mature erythrocytes are mostly oval with smooth surface, oval or round nuclei whose chromatin is denser. The lymphocytes are usually round, with less cytoplasm, and the nucleus is usually eccentrically located. The monocytes are mostly round, the nucleus is round or oval, and vacuoles can be observed in the cytoplasm. Neutrophils are nearly round, and their nuclei are usually eccentrically located, lobed, kidney or oval shaped, with clear nucleoplasm boundaries. Eeosinophils are usually round, with reniform or oval nuclei, and the cytoplasm is filled with purple granules. Thrombocytes have various forms, most of which are oval, spindle, long-rod shaped or teardrop shaped, and their nucleo-cytoplasmic ratio is large. The lymphocytes were positive for periodic acid-Schiff reaction (PAS), weakly positive for naphythol AS-D chloroacetate esterase (AS-DCE) and α-naphthol ace-tate esterase (ANAE), and negative for Sudan black B (SBB), acid phosphatase (ACP), alkaline phosphatase (AKP) and peroxidase (POX). The monocytes were strongly positive for POX and ACP, while PAS, positive for SBB, AS-DCE and ANAE were and negative for AKP. Except weakly positive for PAS and ANAE, the cytochemical staining pattern of neutrophils were the same as those of monocytes. Eosinophils showed strong positive for POX and ANAE, positive for SBB and ACP, weak positive for PAS and AS-DCE, and negative for AKP. The thrombocytes were weakly posi-tive for PAS, AS-DCE and ANAE and negative for SBB, ACP, AKP and POX. The microstructural and cytochemical characteristics of peripheral blood cells in Megalobrama amblycephala were similar to those of other fishes, but also had obvious species specificity. The results of this investigation can be used as a basis for monitoring the health status of Megalobrama amblycephala and provide basic data for its farming and pathological diagnosis.