Effect of cobalt salts on the glycemia and islet histology of Channa punctatus (Bloch).

Channa punctatus responds to the intramuscular administration of cobalt chloride and cobalt nitrate by exhibiting an increase in the blood glucose level. The hyperglycemia persists till 120 h, after which the fish become moribund and ultimately die. Cobalt salts evoke degranulation and vacuolization of the alpha-cells in the initial stage but later the beta-cells are also found to be severely damaged. Cobalt chloride has been found to be more toxic than the cobalt nitrate.