The environment experienced during embryonic development is a rich source of phenotypic variation, as environmental signals have the potential to both inform adaptive plastic responses and disrupt normal developmental programs. Environment-by-embryo interactions are particularly consequential for species with temperature-dependent sex determination, a mode of sex determination common in non-avian reptiles and fish, in which thermal cues during a discrete period of development drive the formation of either an ovary or a testis. Here we examine the impact of thermal variation during incubation in combination with developmental exposure to a common endocrine-disrupting contaminant on fitness-related hatchling traits in the American alligator (Alligator mississippiensis), a species with temperature-dependent sex determination. Using a factorial design, we exposed field-collected eggs to five thermal profiles (three constant temperatures, two fluctuating temperatures) and two environmentally relevant doses of the pesticide metabolite dichlorodiphenyldichloroethylene; and we quantified incubation duration, sex ratios, hatchling morphometric traits, and growth (9–10 days post-hatch). Whereas dichlorodiphenyldichloroethylene exposure did not generally affect hatchling traits, constant and fluctuating temperatures produced diverse phenotypic effects. Thermal fluctuations led to subtle changes in incubation duration and produced shorter hatchlings with smaller heads when compared to the constant temperature control. Warmer, male-promoting incubation temperatures resulted in larger hatchlings with more residual yolk reserves when compared to cooler, female-promoting temperatures. Together, these findings advance our understanding of how complex environmental factors interact with developing organisms to generate phenotypic variation and raise questions regarding the mechanisms connecting variable thermal conditions to responses in hatchling traits and their evolutionary implications for temperature-dependent sex determination.

中文翻译：

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孵化温度和母体资源供应，但不是污染物暴露，具有温度依赖性性别决定的物种中的形状孵化表型

胚胎发育过程中经历的环境是表型变异的丰富来源，因为环境信号有可能通知适应性塑料反应并破坏正常的发育程序。环境与胚胎的相互作用对于具有温度依赖性性别决定的物种尤其重要，这是一种在非鸟类爬行动物和鱼类中常见的性别决定模式，其中离散发育时期的热线索驱动卵巢或卵巢的形成。一个睾丸。在这里，我们研究了孵化过程中的热变化以及发育暴露于常见的内分泌干扰污染物对美洲短吻鳄（密西西比短吻鳄）与健康相关的孵化性状的影响)，一种具有温度依赖性性别决定的物种。使用析因设计，我们将田间采集的鸡蛋暴露于五种温度曲线（三种恒温、两种波动温度）和两种环境相关剂量的农药代谢物二氯二苯二氯乙烯；我们量化了孵化持续时间、性别比例、孵化形态特征和生长（孵化后 9-10 天）。虽然二氯二苯基二氯乙烯暴露通常不会影响孵化性状，但恒定和波动的温度会产生不同的表型效应。与恒温控制相比，热波动会导致孵化持续时间发生细微变化，并产生较短的幼龟，头部较小。更暖和，与较冷的促进雌性的温度相比，促进雄性的孵化温度会导致更大的幼龟具有更多的剩余蛋黄储备。总之，这些发现促进了我们对复杂环境因素如何与发育中的生物体相互作用以产生表型变异的理解，并提出了关于将可变热条件与孵化性状反应联系起来的机制及其对温度依赖性性别决定的进化影响的问题。