抄録
Abstract: We examined whether exposure to predators affects the shell preference of the hermit crab Pagurus filholi. First, hermit crabs occupying the shells of three gastropods(Batillaria cumingi, Reticunassa fraterculus, and Homalopoma sangarense)were exposed to the predatory crab Gaetice depressus. B. cumingi shells provided the most protection, and H. sangarense shells provided the least protection against predation. We then used these two shell species for shell preference tests conducted in both the presence and absence of the predator. We placed 20 hermit crabs(10 in B. cumingi shells and 10 in H. sangarense shells)collected from the field into a plastic container that contained 100 empty shells of each species to allow them to select their preferred shell species and size. After this first shell selection, we divided the hermit crabs that occupied each shell species into two groups of approximately equal number. We then introduced two predatory crabs and a crushed piece of P. filholi everyday into one group but not the other. After 10 days we conducted a second shell selection experiment and compared the utilization frequencies of the 1st and 2nd shell selections for each group. Hermit crabs exposed to the predatory crabs increased their preference for B. cumingi shells over H. sangarense shells. On the other hand, crabs not exposed to predatory crabs increased their preference for H. sangarense shells, perhaps because they are lighter than B. cumingi shells. Our results suggest that shell preference of the hermit crab varies depending on environmental factors such as the threat of predation.
