Microcystin-LR Affects Ultimobranchial Gland of Catfish Heteropneustes fossilis

Microcystin-LR (2.5 µg/25 g) was injected intraperitoneally to the fish Heteropneustes fossilis on day 1, 10 and 20 kept in either freshwater or freshwater containing ZnCl₂. The fishes were killed on day 5, 10, 20 and 30 day. The serum calcium levels was estimated and ultimobranchial glands were processed for routine histology. Microcystin-LR administration to fish Heteropneustes fossilis induced hypocalcemia and ultimobranchial gland exhibit decreased nuclear volume of the ultimobranchial cells. Degenerative ultimobranchial gland cells were obtained after day 20. While the fish injected with MC-LR kept in ZnCl₂ has shown no change in serum calcium levels as well as in histology of ultimobranchial gland cells.