Thermal tolerance of intertidal and subtidal adults and embryos of the marine gastropod Crepipatella peruviana

The calyptraeid gastropod Crepipatella peruviana lives both intertidally and subtidally and broods its embryos within the mantle cavity for several weeks before releasing the offspring as veliger larvae. Adults and advanced embryos collected intertidally and subtidally at Puerto Montt, Chile, were exposed for up to 3 h to elevated temperatures between 29 and 32 degrees C (control temperature was 20 degrees C); we then quantified physiological shifts over the next 24 h and assessed mortality 24 and 48 h after the stress was ended. For both intertidal and subtidal adults, even a 1 h exposure to thermal stress as low as 30 degrees C reduced rates of feeding and oxygen consumption dramatically; those rates did not recover to control levels over the subsequent 24 h, suggesting a high degree of physiological stress. Based on 48 h survival, intertidal adults were significantly more sensitive to thermal stress than were subtidal adults, whereas intertidal advanced embryos were more resistant to thermal stress than their subtidally collected counterparts. Moreover, intertidal advanced embryos were at least as tolerant of thermal stress as intertidal adults were. In contrast, subtidal advanced embryos seemed less tolerant of thermal stress than subtidal adults. For both embryos and adults, regardless of where they were collected, mortality following thermal stress was substantially greater 48 h after the stress period than after 24 h. Future studies will be required to determine the cause of this mortality and the factors responsible for the differences in susceptibility to thermal stress documented in this study.