Heat shock protein expression in relation to reproductive cycle in land snails: Implications for survival

Land snails are subject to daily and seasonal variations in temperature and in water availability and use heat shock proteins (HSPs) as part of their survival strategy. We tested whether the reproductive cycle of land snails affects the endogenous levels of HSPs, and their involvement in the reproductive process. We examined HSP levels in the foot tissue of two Sphincterochila species, S. cariosa and S. zonata, before and after laying eggs, and analyzed the albumen gland (reproductive organ) of both species and eggs of S. cariosa for the presence and quantity of various HSPs. Our study shows reduction in the expression level of Hsp70 isoforms and Hsp90 in S. zonata foot and of Hsp74 in S. cariosa foot during the period preceding egg laying compared to the post-reproductive stage. Hsp70 isoforms and Hsp25 were highly expressed in both large albumen glands and in freshly laid eggs of S. cariosa, whereas large albumen glands of S. zonata expressed mainly Hsp70 isoforms. We conclude that a trade-off between survival and fertility is responsible for the expression level of HSPs in the foot tissue of Sphincterochila snails. Our study shows that HSPs are involved in the reproductive process. We propose that parental provision of HSPs may be part of a "be prepared" strategy of Sphincterochila snails, and that HSPs may play important roles in the survival strategy of land snails during the early life stages. Our observations also highlight the importance of the reproductive status in study of whole organisms, especially when assessing the HSP response to stress.