Response of Ultimobranchial and Parathyroid Glands of the Indian Skipper Frog, Euphlyctis cyanophlyctis to Cadmium Toxicity

Background: Cadmium toxicity has been shown in aquatic animals but the effect on frog’s endocrine glands is not known. We investigated the effects of cadmium on ultimobranchial and parathyroid glands of Indian skipper frog, Euphlyctis cyanophlyctis. Methods: Frogs were exposed to cadmium chloride for short and long terms and sacrificed after 24, 48, 72 or 96 h (short-term) and after 5, 10, 15 and 30 days (long-term). Results: After 48h of cadmium exposure, serum calcium levels decreased and persisted for 96h. After 96h of exposure, weak staining of the ultimobranchial cells was noted, and the nuclear volumes decreased. The histological structures of parathyroid cells remained unchanged. Frogs exposed to cadmium exhibited decreased serum calcium levels from day 10 to day 30.  After 15 days of cadmium exposure, ultimobranchial cells exhibited a decline in staining response and the nuclear volume also decreased. The follicular epithelia of the ultimobranchial glands appeared to be reduced at certain areas. After 30 days of cadmium exposure, the nuclear volume was further decreased and the follicular epithelia shrunk and appeared as a single layer. Cellular degeneration and vacuolization were also noticed in the gland. After day 15 of cadmium exposure, the nuclear volume of the parathyroid cells increased with elongated and hyperchromatic appearance. These changes were exaggerated on day 30 of cadmium exposure and few cell lyses appeared among parathyroid cells. Conclusions: Cadmium adversely affected the calcium regulating glands, ultimobranchial and parathyroid glands of the Indian frogs, Euphlyctis cyanophlyctis.