The effect of maternal environment on the stress response during the embryonic development of a freshwater gastropod: a common garden experiment testing the difference in effect from maternal and developmental environments

The effect of maternal and developmental environment on the onset and level of stress response was investigated in the freshwater gastropod Radix balthica using a common garden experiment. Embryos from two maternal environments (M1APW and M2ASW) were reared in both the same environment as their mothers and in an altered saline environment. Onset of initial foot attachment (IFA) which determines the start of crawling behaviour (stress proxy used) was identified between maternal and developmental environments. Crawling activity pre and post stress exposure was measured, which gave the rate of change in time spent crawling between the two. In order to asses crawling performance according to different maternal environments, the thermal sensitivity was measured in response to ramping temperatures. Results showed no difference in the onset of IFA between maternal environment and between developmental environments. A subtle difference was found in time spent crawling pre-stress exposure in saline (ASW) embryos from ASW-exposed mothers with embryos spending less time crawling compare to other embryos. Results also suggested that developmental environment had a strong selection effect on the rate of change in time spent crawling between pre and post stress exposure as well as for time spent crawling during acute stress exposure. ASW developmental environment was the reason for differences found in crawling performance, as embryos kept in ASW environment from both pond water (APW) and ASW maternal environments had increased thermal sensitivity as opposed to APW embryos from each maternal environment. This study demonstrates that developmental environment may play a crucial role during ontogeny and might overcome maternal environment in terms of stress response