Effects of water temperature on embryonic development in the northern Pacific asteroid, Asterias amurensis, from the southern coast of Korea

Abstract

Although the starfish, Asterias amurensis, has been known to cause severe damage to benthic shellfish populations through predation, few studies have been made of the basic biology of this species in Korean waters. Laboratory experiments were performed to obtain information on the effects of temperature on the embryonic development during the early life stage of A. amurensis. Developmental time decreased as temperature increased, and the elapsed time to develop to the bipinnaria larva at 10, 15, and 20degreesC was 120, 72, and 60 h, respectively. The average biological minimum temperature was estimated to be 0.97degreesC. The cumulative water temperatures for some developmental stages from 2-cell to bipinnaria larva were calculated. Temperature did not affect the fertilization rate (p = 0.866), while it significantly affected the rate of hatching and larval normality (p<0.001). Between 10 and 15degreesC, there was no significant difference in the rate of hatching (p = 0.157) and larval normality (p = 0.437). However, at 20degreesC, major reduction in rates of hatching and larval normality were found. We therefore suggest that the optimal temperature for embryonic development of A. amurensis is 15degreesC.