広島県宮島におけるシロスジフジツボの繁殖生態

摘要

As there are few reports about the reproductive ecology of Fistulobalanus albicostatus which is a native species of Japan, reproduction of this species was investigated at the Suginoura quay of Miyajima, Hiroshima Prefecture, Seto Inland Sea from October 2013 to October 2014.Settlement density and aperture length were measured in an 18×18?cm quadrat. And brooding rate (fraction of individuals bearing fertilized eggs) was examined at the tide level below 119?cm from E.H.W.S every month and water temperature and salinity were concurrently measured. As a result, it was estimated that F. albicostatus produced 4,936,000 nauplii per 100?cm~(2) (15,992,000/18×18) in total from the equation by Iwaki (1981). The value was smaller than that obtained from a population at Matoya Bay, and Machiyaura, in Mie Prefecture by Iwaki (2006). The difference might depend on the difference of the immersed time between the two populations examined.The larval production is smaller than that of recently introduced striped barnacle Amphibalanus amphitrite , but the population size of F. albicostatus seemed to have remained stable surpassed the alien species over the recent 20 years due to its ability to tolerate euryhaline conditions.