Cytochemical characterization of peripheral blood cell populations of two Cyprinidae, Carassius auratus and Ctenopharyngodon idellus.

Fish are the most diverse species of all vertebrate groups, and their blood cells have shown variable characteristics in terms of morphology. Cytochemical staining for enzyme activity in blood leukocytes will help assess the immune function of fish. We characterize blood cells from crucian carp (Carassius auratus) and grass carp (Ctenopharyngodon idellus) by using a Diff-Quick stain as well as different cytochemical methods. Blood specimens obtained from crucian carp and grass carp were evaluated after cytochemical staining for acid phosphatase (ACP), alkaline phosphatase (ALP), naphthol AS chloroacetate esterase (AS-DNCE), naphthyl acetate esterase (NAE), α-naphthyl butyrate esterase (NBE), peroxidase (MPO) and periodic acid-Schiff's reaction (PAS) using commercial kits. Blood cell types were evaluated based on their morphological characteristics and the presence or absence of specific chromogen. The expression pattern of enzymes was similar between the two Cyprinidae and was also broadly consistent with other fish species. However, there were some interesting differences detected between crucian carp and grass carp, including naphthol AS chloroacetate esterase activity in monocytes, peroxidase activity and location in thrombocytes. The ACP, ALP and MPO expressions of different leukocytes of the two Cyprinidae were evaluated by Image Pro Plus and were analysed for statistical significant differences. This investigation provides basic haematology and enzyme activity analyses for crucian carp and grass carp and serves as an approach to evaluating the immune response of fish.