Meeting Abstract
Environmental pollution and climate change can bias the sex ratios of animal populations in which sexual development in sensitive to environmental contaminants and temperature. Investigating these effects in field studies and ecotoxicological experiments is important but difficult when males and females cannot be distinguished without sacrificing them. We examined the utility of skin coloration as a non-invasive sex marker in juvenile common toads (Bufo bufo) that appear sexually monomorphic. We raised toadlets in the lab, and exposed the tadpoles to one of six treatments: two concentrations of two feminizing pollutants each and two controls. Before the first hibernation, we measured the hue, saturation and brightness of the toadlets’ dorsal skin from photographs, and sexed them by inspecting their gonads. We found significant sexual dichromatism with males being yellower-greener and brighter than females. Although only 34% of males and 85% of females could be categorized correctly from photographs, the ratio of greenish and reddish individuals as categorized subjectively by human vision correlated strongly with the sex ratio of treatment groups. Treatment with 1 µg/L 17α-ethinylestradiol resulted in 100% females, with similar coloration as normal females. Intersex individuals occurred in treatment groups with 3 µg/L glyphosate and 1 ng/L 17α-ethinylestradiol; these animals were less saturated and darker reddish-brown compared to normal individuals. These results suggest that skin coloration may help in assessing phenotypic sex and gonadal abnormalities in common toads.
