The Effects of Atrazine and Temperature on Turtle Hatchling Size and Sex Ratios

Abstract

Temperature influences some hormone-governed developmental processes, as do environmental contaminants known as endocrine-disrupting compounds. Although many vertebrates exhibit developmental sensitivity to temperature or contaminants, little research has focused on the potential interaction of these two external influences during development. Here, embryos of the red-eared slider turtle (Trachemys scripta elegans) are used to model the potential interaction of increased temperature and the herbicide atrazine. The atrazine level selected (0.5 parts per billion) was based on common environmental concentrations and is within the range of federally approved drinking-water levels. Sex ratio was the endpoint of population effect in this study, with an increase in females construed as an effect of either temperature, atrazine, or the two together. Mass, carapace length and width, and plastron length were also assessed as endpoints of individual effects of exposure. Results show that increased temperature or atrazine alone do not affect sex ratio, but that the two interact to significantly increase the female fraction. Plastron length, carapace length and width, and mass were higher in atrazine-exposed turtles kept at the lower temperature, a result with fitness implications.