Effects of the insecticide cypermethrin on plasma calcium and ultimobranchial gland of a teleost, Heteropneustes fossilis.

Heteropneustes fossilis were subjected to 5.76 and 1.44 microg/L of cypermethrin for short- and long-term experiments, respectively. Fish were sacrificed at 24, 48, 72, and 96 h in the short-term and 7, 14, 21, and 28 days in the long-term experiment. Plasma calcium levels were determined. Ultimobranchial glands were fixed for histological studies. Plasma calcium levels of fish exhibit a decrease after 48, 72, and 96 h. After 96 h a decrease in the staining response of the cytoplasm of ultimobranchial cells has been noticed. The nuclear volume of these cells undergoes a slight decrease. Chronically exposed fish exhibit a decrease in calcium level on day 7 which persists through 28 days. After 21 days, nuclear volume of the ultimobranchial cells undergoes a decrease and these cells exhibit a slight decrease in the staining response of the cytoplasm. Following 28 days exposure, the nuclear volume undergoes further decrease and degeneration and vacuolization sets in.