Vanthournout B, Deswarte K, Hammad H, Bilde T, Lambrecht B, Hendrickx F
Terrestrial Ecology Unit, Department of Biology, Ghent University, Ledeganckstraat 35, 9000 Ghent, Belgium Department of Bioscience, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark
Laboratory of Immunoregulation and Mucosal Immunology, Department for Molecular Biomedical Research, VIB, Ghent 9050, Belgium.
Biol Lett. 2014 May;10(5):20140159. doi: 10.1098/rsbl.2014.0159.
Producing equal amounts of male and female offspring has long been considered an evolutionarily stable strategy. Nevertheless, exceptions to this general rule (i.e. male and female biases) are documented in many taxa, making sex allocation an important domain in current evolutionary biology research. Pinpointing the underlying mechanism of sex ratio bias is challenging owing to the multitude of potential sex ratio-biasing factors. In the dwarf spider, Oedothorax gibbosus, infection with the bacterial endosymbiont Wolbachia results in a female bias. However, pedigree analysis reveals that other factors influence sex ratio variation. In this paper, we investigate whether this additional variation can be explained by the unequal production of male- and female-determining sperm cells during sperm production. Using flow cytometry, we show that males produce equal amounts of male- and female-determining sperm cells; thus bias in sperm production does not contribute to the sex ratio bias observed in this species. This demonstrates that other factors such as parental genes suppressing endosymbiont effects and cryptic female choice might play a role in sex allocation in this species.
长期以来，产生等量的雄性和雌性后代一直被认为是一种进化上稳定的策略。然而，许多分类群都记录了这一普遍规律的例外情况（即雄性和雌性偏差），这使得性别分配成为当前进化生物学研究的一个重要领域。由于存在众多潜在的性别比例偏差因素，确定性别比例偏差的潜在机制具有挑战性。在矮蜘蛛吉氏艾蛛（Oedothorax gibbosus）中，感染细菌内共生菌沃尔巴克氏体（Wolbachia）会导致雌性偏差。然而，谱系分析表明，其他因素也会影响性别比例的变化。在本文中，我们研究了这种额外的变化是否可以通过精子产生过程中雄性和雌性决定精子细胞的不平等产生来解释。通过流式细胞术，我们发现雄性产生等量的雄性和雌性决定精子细胞；因此，精子产生的偏差并不是导致该物种观察到的性别比例偏差的原因。这表明其他因素，如抑制内共生菌效应的亲本基因和隐秘的雌性选择，可能在该物种的性别分配中发挥作用。
