Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan.
Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan.
Comp Biochem Physiol A Mol Integr Physiol. 2020 Jul;245:110701. doi: 10.1016/j.cbpa.2020.110701. Epub 2020 Apr 13.
The pejerrey is an atherinopsid species from South America that presents a combination of genotypic and environmental (temperature-dependent) sex determination whereby low and high temperatures induce feminization and masculinization, respectively. Masculinization involves a heat-induced stress response leading to increased circulating cortisol and androgens. We tested whether crowding would elicit a similar response as high temperature and affect the sex ratios of pejerrey. Larvae with XX and XY genotypes were reared at 15, 62 and 250 larvae/L in 0.4, 1.6, and 6.4 L containers during a period considered critical for sex determination at 25 °C, a mixed-sex promoting temperature. Fish were analysed at 3-7 weeks for whole-body cortisol and 11-ketotestosterone (11-KT) titer and hydroxy-steroid dehydrogenase (hsd11b2) mRNA transcript abundance, and after completion of gonadal sex differentiation (10-14 weeks) for determination of phenotypic and genotypic sex mismatches. Crowding was associated with depressed growth, higher cortisol and 11-KT titers, increased hsd11b2 transcription, and increased frequency of masculinization compared to intermediate and/or low rearing densities. Perceived crowding (by rearing in containers with mirror-finish, reflecting walls) also caused masculinization. These results suggest the possibility that other environmental factors besides temperature can also affect sex determination in pejerrey and that a stress response leading to increased cortisol and androgen levels, which is potentially perceived by the brain, may be a common feature among different forms of environmental sex determination in this species.
褐首脂鲤是一种来自南美洲的脂鲤科鱼类，具有基因型和环境（温度依赖型）性别决定的组合，即低温和高温分别诱导雌性化和雄性化。雄性化涉及热诱导应激反应，导致循环皮质醇和雄激素增加。我们测试了拥挤是否会像高温一样引起类似的反应，并影响褐首脂鲤的性别比例。具有 XX 和 XY 基因型的幼鱼在 25°C 下被认为是性别决定的关键时期，在 0.4、1.6 和 6.4 L 容器中以 15、62 和 250 尾/L 的密度在 25°C 下饲养，这是一个促进混合性别比例的温度。在 3-7 周时，对所有鱼进行全身皮质醇和 11-酮睾酮（11-KT）滴度以及羟基甾体脱氢酶（hsd11b2）mRNA 转录丰度分析，在完成性腺性别分化（10-14 周）后，确定表型和基因型性别不匹配。与中等和/或低密度饲养相比，拥挤与生长抑制、皮质醇和 11-KT 滴度升高、hsd11b2 转录增加以及雄性化频率增加有关。与具有镜面反射壁的容器中饲养相比，拥挤还会导致雄性化。这些结果表明，除了温度之外，其他环境因素也可能影响褐首脂鲤的性别决定，并且导致皮质醇和雄激素水平升高的应激反应，这可能被大脑感知，可能是该物种不同形式的环境性别决定的共同特征。
