Affiliation:
1. School of Biological Sciences, Illinois State University, Normal, IL 61790, USA
2. Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996-1610, USA
Abstract
Most organisms are exposed to bouts of warm temperatures during development, yet we know little about how variation in the timing and continuity of heat exposure influences biological processes. If heat waves increase in frequency and duration as predicted, it is necessary to understand how these bouts could affect thermally sensitive species, including reptiles with temperature-dependent sex determination (TSD). In a multi-year study using fluctuating temperatures, we exposed
Trachemys scripta
embryos to cooler, male-producing temperatures interspersed with warmer, female-producing temperatures (heat waves) that varied in either timing during development or continuity and then analysed resulting sex ratios. We also quantified the expression of genes involved in testis differentiation (
Dmrt1
) and ovary differentiation (
Cyp19A1
) to determine how heat wave continuity affects the expression of genes involved in sexual differentiation. Heat waves applied during the middle of development produced significantly more females compared to heat waves that occurred just 7 days before or after this window, and even short gaps in the continuity of a heat wave decreased the production of females. Continuous heat exposure resulted in increased
Cyp19A1
expression while discontinuous heat exposure failed to increase expression in either gene over a similar time course. We report that even small differences in the timing and continuity of heat waves can result in drastically different phenotypic outcomes. This strong effect of temperature occurred despite the fact that embryos were exposed to the same number of warm days during a short period of time, which highlights the need to study temperature effects under more ecologically relevant conditions where temperatures may be elevated for only a few days at a time. In the face of a changing climate, the finding that subtle shifts in temperature exposure result in substantial effects on embryonic development becomes even more critical.
Funder
Illinois Lakes Management Association
Phi Sigma Biological Honors Society
American Society of Ichthyologists and Herpetologists
Sigma Xi
Subject
General Agricultural and Biological Sciences,General Environmental Science,General Immunology and Microbiology,General Biochemistry, Genetics and Molecular Biology,General Medicine
Cited by
13 articles.
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