Sex determination and differentiation in reptiles is complex. Temperature-dependent sex determination (TSD), genetic sex determination (GSD) and the interaction of both environmental and genetic cues (sex reversal) can drive the development of sexual phenotypes. The jacky dragon (Amphibolurus muricatus) is an attractive model species for the study of gene–environment interactions because it displays a form of Type II TSD, where female-biased sex ratios are observed at extreme incubation temperatures and approximately 50 : 50 sex ratios occur at intermediate temperatures. This response to temperature has been proposed to occur due to underlying sex determining loci, the influence of which is overridden at extreme temperatures. Thus, sex reversal at extreme temperatures is predicted to produce the female-biased sex ratios observed in A. muricatus. The occurrence of ovotestes during development is a cellular marker of temperature sex reversal in a closely related species Pogona vitticeps. Here, we present the first developmental data for A. muricatus, and show that ovotestes occur at frequencies consistent with a mode of sex determination that is intermediate between GSD and TSD. This is the first evidence suggestive of underlying unidentified sex determining loci in a species that has long been used as a model for TSD.

中文翻译：

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Ovotestes 表明爬行动物模型对温度依赖性性别决定的神秘遗传影响

爬行动物的性别决定和分化是复杂的。温度依赖性性别决定 (TSD)、遗传性别决定 (GSD) 以及环境和遗传线索的相互作用（性别逆转）可以推动性表型的发展。巨龙 (Amphibolurus muricatus) 是研究基因-环境相互作用的有吸引力的模型物种，因为它表现出一种 II 型 TSD，在极端孵化温度下观察到雌性偏向的性别比例，并且发生大约 50:50 的性别比例在中间温度。这种对温度的反应被认为是由于潜在的性别决定基因座而发生的，其影响在极端温度下会被覆盖。因此，预计极端温度下的性别逆转会产生在 A. muricatus 中观察到的女性偏向性别比例。卵睾在发育过程中的出现是密切相关的物种 Pogona vitticeps 中温度性别逆转的细胞标志物。在这里，我们提供了 A. muricatus 的第一个发育数据，并表明卵睾发生的频率与 GSD 和 TSD 之间的性别决定模式一致。这是长期被用作 TSD 模型的物种中潜在的未知性别决定基因座的第一个证据。