Correlation of embryonic temperature sensitivity of sea urchins with spawning season

Abstract

In the coastal waters of Japan, from the subtropical area to the subfrigid area, there are several species of sea urchin with a different biogeographic distribution. The present study investigated the temperature sensitivity, as represented by the range of temperature optima for the embryos, and the dependence of developmental velocity on temperature within that range, for each of eight species of sea urchin, Echinometra mathaei, Diadema setosum, Anthocidaris crassispina, Clypeasterjaponicus, Pseudocentrotus depressus, Hemicentrotus pulcherrimus, Strongylocentrotus nudus and Strongylocentrotus intermedius. For all of these species, the optimal temperature range was confirmed to correspond well with the range of seawater temperature during the spawning season. The distributions of these sea urchins were generally correlated with their embryonic temperature sensitivities but exceptions to this correlation were found. This departure from the correlation as well as the flexibility of embryonic temperature sensitivity are discussed.