2018 年 47 巻 p. 101-110
Salinity is an important ecological factor affecting larval survival and development of coastal and estuarine decapod crustaceans. We investigated the low salinity tolerance limits of larvae in the six terrestrial hermit crab species, the coconut crab Birgus latro, and the land hermit crabs Coenobita brevimanus, C. cavipes, C. purpureus, C. rugosus, and C. violascens to infer their early life history strategies. Zoeae and megalopae were exposed to six different salinity levels ranging from 5–30 ppt with intervals of 5 ppt for 24 h, and the median lethal salinity (MLS) was estimated as the salinity at which 50% of test larvae died. The MLS estimates were lowest in the first zoeae, increased during the zoeal stage, and declined in the megalopal stage in all species. Early zoeae and megalopae were euryhaline and later zoeae stenohaline, suggesting that coenobitids exhibit a larval export strategy towards the offshore (oceanic) marine waters. Interspecific variation was evident in the salinity tolerance of the first zoeae, probably reflecting the salinity conditions at the species-specific larval hatching place. In contrast, the low salinity tolerance ability of megalopae did not differ among species, suggesting that coenobitid megalopae might require similar habitats for the settlement and initiation of benthic life.
