DDT-like effects as a result of corticosterone treatment in an anuran amphibian: Is DDT a corticoid mimic or a stressor?

Exposure of tadpoles to dichlorodiphenyl trichloroethane (DDT) induces pathological development of the upper mandible. In the current study, we report a similar pathological development after tadpoles of the Senegal walking frog (Kassina senegalensis: Hyperolidae) were treated with the steroid hormone, corticosterone (CORT) for 5 d at 1.1 μM. Corticosterone-treated tadpoles developed a “hole” in the snout (mandibular fenestration) with complete loss of the upper keratinized beak, denticles, and oral papillae. Histological analysis revealed a loss of connective tissue, epidermis, and dermis, but remaining dermis, dermal skin glands, and epidermis appeared normal. Analysis of cleared and stained specimens showed that there was no loss of chondrocranial elements but that the cornu trabeculae was eroded, and the cartilago infrarostralis was repositioned and reshaped. The similarities in the effects of CORT reported in the current study and the previously reported effects of DDT suggest that DDT “mimics” CORT or that DDT acts as a “stressor” causing an increase in endogenous CORT. These data are important in defining the effects and mechanisms of pesticide action on anuran larval development.