Tamechika Masami M, Yamada Hiroyuki, Ijiri Shigeho, Yusa Yoichi
Laboratory of Marine Biology, Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Japan.
Faculty of Science, Ehime University, Matsuyama, Japan.
J Evol Biol. 2025 Feb 27;38(3):417-429. doi: 10.1093/jeb/voaf007.
Sex allocation theory predicts the adaptive allocation of resources to male versus female reproduction in simultaneous hermaphrodites in response to individual characteristics or environmental factors. Because parasites uptake resources from their hosts, their presence could affect the sex allocation of the hosts. We investigated the effects of infestation status and infestation intensity by the rhizocephalan barnacle Boschmaella japonica on reproduction, including sex allocation, of the host intertidal barnacle Chthamalus challengeri. Feeding activity was also examined as a factor related to resource intake. Both male and female reproductive investment decreased with increasing parasite infestation, and the sex allocation of large-infested hosts was more male-biased than that of large uninfested hosts. Moreover, in contrast to the model prediction that male investment does not change under resource limitation, male investment decreased in infested hosts whose resources were taken by parasites. This reduction in male investment could be explained by changes in mating group size, since infested hosts have shorter penises and consequently are able to access fewer mating partners.
性分配理论预测，在同时具有雌雄两性的雌雄同体生物中，资源会根据个体特征或环境因素适应性地分配到雄性和雌性繁殖中。由于寄生虫从宿主摄取资源，它们的存在可能会影响宿主的性分配。我们研究了根头藤壶日本博氏藤壶的侵染状态和侵染强度对潮间带藤壶挑战者小藤壶宿主繁殖（包括性分配）的影响。摄食活动也作为与资源摄取相关的一个因素进行了研究。随着寄生虫侵染程度的增加，雄性和雌性的生殖投资均下降，重度侵染宿主的性分配比未受侵染的大型宿主更偏向雄性。此外，与资源限制下雄性投资不变的模型预测相反，在资源被寄生虫摄取的受侵染宿主中，雄性投资减少。雄性投资的这种减少可以通过交配群体大小的变化来解释，因为受侵染的宿主阴茎较短，因此能够接触到的交配伙伴较少。
