Responses of the ultimobranchial gland to vitamin D3 treatment in freshwater mud eel, Amphipnous cuchia, kept in different calcium environments.

Freshwater mud eel, Amphipnous cuchia, were injected intraperitoneally daily with 100 ng of vitamin D3/100 g body weight and maintained in media containing either no calcium or different calcium concentrations. The eels were killed after 1, 3, 5, 10 and 15 days following the treatment and their serum calcium levels were measured. The ultimobranchial glands were fixed and processed using the routine paraffin method for histological studies. The results of the present study indicate that vitamin D3 can induce hypercalcaemia in eels kept in different calcium environments. Also, the ultimobranchial glands became hyperactive following vitamin D3 treatment. It is concluded that in mud eels, the gland has a calcium-regulating function.