Tamoxifen stimulates gonad development and somatic growth in the tadpoles of Indian skipper frog, Euphlyctis cyanophlyctis

Background Endocrine disruptors are one of the major threats to aquatic animals affecting their development and physiology. Amphibians are very sensitive to aquatic contaminants as their skin is semi-permeable. Several contaminants easily enter into their body, act as endocrine disruptors, and interfere in sexual development and metamorphosis. Endocrine disruptors have diverse effects in different species mainly due to the variations in developmental patterns. In the present study, I evaluated the endocrine disrupting potential of tamoxifen (anti-estrogen) in the tadpoles of Indian skipper frog Euphlyctis cyanophlyctis with undifferentiated type of gonad differentiation (testis differentiates through an ovarian phase). Methods I exposed the tadpoles to four concentrations of tamoxifen (25, 50, 100, and 200 μg/l) during larval development (Gosner stages 25–42) and studied their metamorphosis, somatic and sexual development. Results Tamoxifen does not influence gonad differentiation and sex ratio (proportion of males and females). However, all the concentrations of tamoxifen stimulated gonad development resulted in testis maturation in males and increased oocytes size in females. Tamoxifen treatments delayed metamorphosis and stimulated somatic growth. Conclusion These results suggest that tamoxifen does not act as an anti-estrogen in E . cyanophlyctis while stimulate sexual development in both males and females through unknown mechanism. These results are useful to understand the mechanism of action of tamoxifen in lower vertebrates and develop E . cyanophlyctis as an indigenous amphibian model for endocrine disruption studies.