Ecological and population genetic clarification of geographic variation in reproductive cycle of sea urchin

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Reproductive cycle of the sea urchin Strongylocentrotus intermedius differs among sea areas in Hokkaido. This study aims to clarify genetic differences in the populations among sea areas. The reproductive cycle in the Pacific Ocean in Tohoku coincided with that in the Sea of Japan in Hokkaido. There was no significant difference in the mitochondrial DNA sequences among the sea areas, although each different reproductive cycle is closely associated with ocean current, water temperature and distribution of Saccharina kelps established since 10, 000 years ago. A rearing experiment of the sea urchins derived from the Pacific Ocean in southern Hokkaido showed their extremely low growth rate due to high water temperature, suggesting no juvenile recruitment to southern regions from central Miyagi Prefecture.