2021 Volume 76 Pages 1-12
Although sexual segregation (sexual difference in resource use) is versatile in many animal taxa, studies have mostly concentrated on vertebrates. To observe sexual segregation in marine invertebrates, I focused on the sexual differences in shell utilization patterns of hermit crabs. I first reviewed hermit crab biology mainly relating to shell use, including shell acquisition, competition, shell preferences, and influences on fitness components (growth, survival, and fecundity).Then, I considered ecological and evolutionary factors for different shell utilization patterns between sexes observed in Pagurus filholi inhabiting Kattoshi, Hakodate Bay. I integrated the reports on shell species preferences, competitive abilities, and the effects of different shell species on fitness components in P. filholi. Competitive ability for the shells showed no sexual difference. The different shell preferences between sexes were consistent with the field pattern of shell use of the sexes. Females preferred shells which provided them with high fecundity and survival from predators, whereas males preferred shells with high growth potential. As body size is important to males to acquire female mates, high growth is significant for male fitness. Conversely, female fitness greatly depends on the number of eggs produced during their lifetime. In summary, the sexual difference in shell use of P. filholi is mainly determined by different shell preferences by sex, which are ultimately driven from different priorities between sexes to maximize fitness.
