Effects of MCPA Herbicide on Hematological Parameters and Ultrastructure of Hematopoietic Tissues of Common Carp (Cyprinus carpio L.)

Common carp juveniles were subjected to 14 day exposure to 100 mu g/l of MCPA (phenoxy acid herbicide) and 30 day depuration. Peripheral blood parameters were analyzed after 1, 3, 7 and 14 days of exposure at 7, 14 and 30 days of depuration. Ultrastructure of hematopoietic tissues of head and trunk kidney and spleen were analyzed after the end of exposure and purification. Results showed that MCPA exposure induced only minor and transient alterations in red blood parameters but more pronounced changes in leukocyte differential count: a significant and persistent depletion of mature neutrophils during both exposure and depuration, and monocytosis during exposure. These changes indicate a possible inflammatory process and immunosuppression caused by this herbicide. Analysis of hematopoietic tissue revealed no major pathologic lesions but some minor ultrastructural anomalies. Hematopoietic precursor cells with blurred ultrastructure, some vacuoles in cytoplasm with different electron density and size, melanomacrophage and myelin-like structures were observed during exposure and particularly during depuration. These changes indicate a weak cytotoxic effect of MCPA on carp hematopoietic system.