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The effect of hormone manipulations on sex ratios varies with environmental conditions in a turtle with temperature‐dependent sex determination
Author(s) -
Warner Daniel A.,
Mitchell Timothy S.,
Bodensteiner Brooke L.,
Janzen Fredric J.
Publication year - 2017
Publication title -
journal of experimental zoology part a: ecological and integrative physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.834
H-Index - 11
eISSN - 2471-5646
pISSN - 2471-5638
DOI - 10.1002/jez.2085
Subject(s) - nest (protein structural motif) , sex ratio , biology , offspring , turtle (robot) , aromatase inhibitor , painted turtle , aromatase , zoology , ecology , nesting season , seasonal breeder , predation , pregnancy , population , demography , biochemistry , genetics , cancer , sociology , breast cancer
Exogenous application of steroids and related substances to eggs affects offspring sex ratios in species with temperature‐dependent sex determination (TSD). Laboratory studies demonstrate that this effect is most pronounced near the constant temperature that produces 1:1 sex ratios (i.e., pivotal temperature). However, the impact of such chemicals on sex determination under natural nest temperatures (which fluctuate daily) is unknown, but could provide insight into the relative contributions of these two factors under natural conditions. We applied estradiol (E2) and an aromatase inhibitor (fadrozole) to eggs of the painted turtle ( Chrysemys picta ), a species with TSD, and allowed eggs to incubate under natural conditions during two field seasons (in 2012 and 2013). Exogenous E2, fadrozole, and nest temperature contributed to variation in offspring sex ratio, but the relative contributions of these factors differed between years. In 2012, a much hotter than average season, sex ratios were heavily female biased regardless of nest temperature and chemical treatment. However, in 2013, a milder season, both nest temperature and chemical treatment were important. Moreover, a significant interaction between nest temperature and treatment demonstrated that exogenous estradiol induces female development regardless of nest temperature, but aromatase inhibition widens the range of temperatures that produces both sexes.