近日，华中农业大学鱼类遗传育种与繁育实验室沈志刚副教授团队研究成果以“High-temperature stress will put the thermo-sensitive teleost yellow catfish （Tachysurus fulvidraco） in danger through reducing reproductivity”为题在Ecotoxicology and Environmental Safety发表。研究以黄颡鱼为研究对象，揭示了全球变暖背景下持续上升的高温环境，将通过削弱种群繁殖力，而对性别分化热敏鱼类的种群维持产生潜在威胁。
全球温度升高已成为不争的事实，全球表面平均温度在以每十年提升0.19℃的速度增长，这可能在未来百年内导致数千种物种灭绝。鱼类作为低等脊椎动物，物种数量多，生境分布广，其性别分化最具多样性和复杂性。目前普遍接受的观点是，雌雄异体鱼类的性别是由遗传（GSD）、环境（ESD）或两者的相互作用（GSD+EE）决定的。据报道，环境应激包括极端温度、种群密度、明亮的背景颜色、低溶氧、非中性pH值和食物丰度/质量低等所有环境应激源，普遍性地导致鱼类雄性化或种群雄性比例增加。因此，全球环境变暖可能通过改变性别分化方向，打破种群有效性别比例，从而间接推动热敏鱼类物种灭绝。团队前期研究发现，黄颡鱼属于GSD+EE鱼类，高温能诱导部分XX遗传型雌性个体雄性化，是研究环境与性别分化关联的极好对象。
该研究通过三个方面表明全球变暖（高温环境）会削弱热敏硬骨鱼物种种群持续性。首先，沈志刚团队建立了多个黄颡鱼家系，将不同家系幼鱼在性别分化温度敏感时期暴露于高温环境，模拟极端升温气候。通过性别特异性分子标记与性腺组织学分析，确定了高温普遍诱导各家系XX遗传型雌鱼雄性化，但存在明显的家系差异。其次，通过性腺组织学和计算机辅助精子分析系统，确定了XX伪雄鱼繁殖性能显著低于正常XY雄鱼。最后，团队将XX与XY遗传型个体暴露于环境胁迫中（包括高温、寄生虫和低氧胁迫），发现XY遗传型在环境胁迫下表现出更低的存活率。
此外，该研究还结合数学模型，预测了性别分化热敏鱼类在全球变暖大背景下种群性比的变化规律。
综上所述，全球变暖引发的高温胁迫将从诱导XX遗传型雌鱼雄性化、削弱XX伪雄鱼生殖性能和导致XY遗传型雄性特异性高死亡率这三方面，使性别分化热敏性硬骨鱼类物种长期处于潜在的生存威胁之中。
华中农业大学硕士研究生于跃为论文的第一作者，沈志刚副教授为论文的通讯作者。本研究得到了中央高校基本科研业务费专项资金和湖北省自然科学基金的资助。
【英文摘要】
Recently, concerns for species that sex differentiation is influenced by temperature in the context of global warming have increased because disrupted operational sex ratios could threaten population maintenance. In contrast, little attention has been given to the reproductive ability of populations that experienced elevated temperatures. In this study, we demonstrated that high temperature （HT） would decrease population size via three different aspects of reproductive ability for the first time. We show that, in a thermo-sensitive teleost yellow catfish, a short period of HT （+3 ?C） exposure during the critical period of sex differentiation leads to a different percentage of masculinization of XX genotypic females （1–23%） in wet-lab and natural water bodies. Combining the results of gonadal appearance, histology, sperm parameters, and fertilization rate, we found that XX pseudo- males induced by HT display significantly discounted fertility and reproductive performance compared to XY normal males. We demonstrate that the survival of the XY genotype is lower than XX genotype under environmental stress, including HT, hypoxia, and parasite infection, and the differential survival seems unrelated to male-biased sexual size dimorphism. The mathematical model predicts that the phenotypic female percent will be stabilized at 50% and the population will be sustainably maintained when masculinizing force is less than 0.5, while HT will put the population in danger when the masculinizing force exceeds 0.5. However, when we combine the real-world data of reproductive ability and mathematic model, our results suggest the population size decreases and the long-term survival of the studied species are threatened under the projected pace of increasing temperature. These findings will be useful for understanding the long-term effects of increasing temperature on sex ratio, reproduction and population maintenance in teleost.
论文链接：https://www.sciencedirect.com/science/article/pii/S014765132200478X#bib79
日期：2022-06-13
