Fishman R, Vortman Y, Shanas U, Koren L
The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
Hula Research Center, Department of Animal Sciences, Tel-Hai College, Upper Galilee 1220800, Israel.
R Soc Open Sci. 2018 Sep 5;5(9):171636. doi: 10.1098/rsos.171636. eCollection 2018 Sep.
Population sex ratios naturally fluctuate around equality. It is argued that the production of an equal number of male and female offspring by individual parents should be favoured by selection, if all costs and benefits are equal. Theoretically, an even sex ratio should yield the highest probability for a fetus to be adjacent to a fetus of the opposite sex . This may cause developmental costs or benefits that have been overlooked. We examined the physiological and developmental parameters associated with sex ratios in the nutria (), an invasive wildlife species with a strong reproductive output. Using hair testing, we found that litters with even sex ratios had the highest average cortisol levels. Fetuses neighbouring the opposite sex exhibited longer trunks than those neighbouring the same sex, which might imply better lung development. Our results are the first, to our knowledge, to link intra-utero sex ratios and fetal cortisol and suggest that fetal cortisol might be a mechanism by which even sex ratios are maintained via developmental advantages.
种群的性别比例自然地围绕着平衡状态波动。有人认为，如果所有成本和收益相等，个体亲本生育数量相等的雄性和雌性后代应该会受到自然选择的青睐。从理论上讲，性别比例均衡应该会使胎儿与异性胎儿相邻的概率最高。这可能会导致一些被忽视的发育成本或收益。我们研究了与海狸鼠（一种具有强大繁殖能力的入侵性野生动物）性别比例相关的生理和发育参数。通过毛发检测，我们发现性别比例均衡的窝仔平均皮质醇水平最高。与异性相邻的胎儿比与同性相邻的胎儿躯干更长，这可能意味着肺部发育更好。据我们所知，我们的研究结果首次将子宫内性别比例与胎儿皮质醇联系起来，并表明胎儿皮质醇可能是一种通过发育优势维持性别比例均衡的机制。
