Dispersal for population maintenance in the algae-boring amphipod Ceinina japonica

Abstract

Ceinina japonica, an amphipod of the family Eophliantidae, bores tunnels into laminarian brown algae to construct nests. As for the populations that utilize Undaria pinnatifida, individuals of C. japonica reproduce within the nest, and adults and juveniles coexist for months. The individuals which live inside of the seaweed are protected from predators and utilize resources supplied with the growth of the seaweed. However, U. pinnatifida, an annual seaweed, disappears during the summer. It has been reported that the infestation rates of C. japonica increased in Saccharina japonica var. ochotensis during the period when U. pinnatifida was lost along the coast of Hokkaido. This suggests the seasonal migration of C. japonica and its preferences for laminarian kelps. On the other hand, C. japonica has also been reported as an epifauna on some Sargassum species. Further investigation is needed to determine the identity of the populations occurring in laminarian kelps and on Sargassum seaweeds. In order to elucidate the population maintenance mechanisms of C. japonica, it is necessary to investigate its habitat preferences, adaptation to multiple seaweed species and dispersal patterns.