ABSTRACT: Warming global temperatures are predicted to reduce population viability in many oviparous ectothermic taxa, with increased embryonic mortality likely to be a main cause. While research on embryonic upper thermal limits is extensive, sea turtle hatchling thermal tolerance has received less attention and our understanding of how incubation conditions influence hatchling thermal tolerance is limited. Here, we report green turtle Chelonia mydas hatchling hydration and thermal tolerance following incubation in dry and wet conditions. We used packed cell volume and total protein as indicators of hydration and measured the critical thermal maximum (CT_max) of hatchlings in air. Neither hydration nor thermal tolerance was directly influenced by moisture treatment. However, hatchlings from moister nests had longer incubation durations (wet: 60.11 d vs. dry: 54.86 d), and, using incubation duration as a proxy for incubation temperature, hatchlings from cooler nests had significantly lower CT_max (wet: 39.84°C vs. dry: 40.51°C). Thus, despite not directly influencing thermal tolerance, moisture treatment influenced nest temperature indirectly; hatchlings that experienced warmer conditions in dry nests had a higher thermal tolerance than hatchlings from cooler and wetter nests. Ectothermic neonates may have greater plasticity in their thermal tolerance than previously thought, but their ability to adapt to increasing temperature is likely limited. Additionally, common management techniques to reduce nest temperatures, such as watering and shading nests, may only reduce embryonic mortality at the cost of decreased hatchling thermal tolerance and increased hatchling mortality during emergence. Nesting-site management interventions designed to reduce embryonic mortality will need to consider mitigation of the possible effects of those interventions on hatchling mortality.

中文翻译：

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孵化环境在确定海龟幼体耐热性中的作用

摘要：据预测，全球气温升高会降低许多卵生外热类群的种群生存力，而胚胎死亡率的升高可能是主要原因。尽管对胚胎温度上限的研究很广泛，但海龟孵化的热耐受性却很少受到关注，而且我们对孵化条件如何影响孵化热耐受性的了解也很有限。在这里，我们报道了在干燥和潮湿条件下孵化后的绿海龟Chelonia mydas孵化后的水合作用和耐热性。我们使用填充的细胞体积和总蛋白作为水合指标，并测量了临界热最大值（CT_最大值））在空气中的孵化。水合作用既不影响水合也不耐热。然而，来自潮湿巢的孵化的孵化时间较长（湿：60.11 d vs干燥：54.86 d），并且使用孵育持续时间作为孵化温度的替代品，来自较冷的巢的孵化的CT _max明显较低。（湿：39.84℃，干：40.51℃）。因此，尽管不直接影响耐热性，但水分处理间接影响了巢温度。在干燥巢中经历温暖条件的孵化器比在凉爽和潮湿的巢中孵化的孵化器具有更高的耐热性。发热的新生儿的热耐受性可能比以前认为的要强，但适应温度升高的能力可能受到限制。另外，降低巢温度的常用管理技术，例如浇水和遮荫巢，只能以降低孵化热耐受性和增加出苗期间孵化死亡率为代价来降低胚胎死亡率。