Several New World atheriniforms have been recognized as temperature‐dependent sex determined (TSD) and yet possess a genotypic sex determinant (amhy ) which is primarily functional at mid‐range temperatures. In contrast, little is known about the sex determination in Old World atheriniforms, even though such knowledge is crucial to understand the evolution of sex determination mechanisms in fishes and to model the effects of global warming and climate change on their populations. This study examined the effects of water temperature on sex determination of an Old World atheriniform, the cobaltcap silverside Hypoatherina tsurugae , in which we recently described an amhy homologue. We first assessed the occurrence of phenotypic/genotypic sex mismatches in wild specimens from Tokyo Bay for three years (2014–2016) and used otolith analysis to estimate their birth dates and approximate thermal history during the presumptive period of sex determination. Phenotypic sex ratios became progressively biased towards males (47.3%–78.2%) during the period and were associated with year‐to‐year increases in the frequency of XX‐males (7.3%–52.0%) and decreases in XY/YY‐females (14.5%–0%). The breeding season had similar length but was delayed by about 1 month per year between 2014 and 2016, causing larvae to experience higher temperatures during the period of sex determination from year to year. Larval rearing experiments confirmed increased likelihood of feminization and masculinization at low and high temperatures, respectively. The results suggest that cobaltcap silverside has TSD, or more specifically the coexistence of genotypic and environmental sex determinants, and that it affects sex ratios in wild populations.

中文翻译：

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表皮/基因型的性别不匹配和温度依赖性的性别决定是在旧大陆的atherinid（钴帽银side Hypoatherina tsurugae）的野生种群中进行的。

几种新大陆的动脉粥样硬化形式已被公认为是温度依赖性性别决定的（TSD），但具有主要在中温下起作用的基因型性别决定因素（amhy）。相比之下，尽管旧知识在了解鱼类中性别决定机制的演变以及对全球变暖和气候变化对其种群的影响进行建模方面至关重要，但对旧世界斑状鱼类的性别决定知之甚少。本研究对性别决定一个旧世界atheriniform的cobaltcap银汉水温度的影响Hypoatherina tsurugae，在我们最近描述的amhy同系物。我们首先评估了三年（2014-2016年）东京湾野生标本中表型/基因型性别不匹配的发生，并使用耳石分析法估计了他们在性别确定的假设期间的出生日期和近似的热史。在此期间，表型性别比逐渐偏向男性（47.3％–78.2％），并且与XX-男性的频率逐年增加（7.3％–52.0％）和XY / YY女性的频率下降有关（14.5％–0％）。繁殖季节的长度相似，但在2014年至2016年之间每年延迟约1个月，这导致幼虫在确定性别的期间每年经历更高的温度。幼体饲养实验证实，在低温和高温下女性化和男性化的可能性增加，分别。结果表明，钴银苷具有TSD，或更具体地说是基因型和环境性别决定因素的共存，并且它会影响野生种群中的性别比。