Reproduction and population structure of the sea urchin Heliocidaris crassispina in its newly extended range: The Oga Peninsula in the Sea of Japan, northeastern Japan.

Ocean warming has facilitated the range expansion of commercially important sea urchin species to higher latitudes. Heliocidaris crassispina was recorded to extend northward to Toga Bay along the Oga Peninsula, Japan following an increase in seawater temperatures, and replacement of local sea urchin species Mesocentrotus nudus. In order to identify evidence of adaptation occurring in response to a range extension of H.