Meeting Abstract
23.1 Friday, Jan. 4 Insulin-like signaling and life history trade-offs in garter snakes with divergent life histories ADDIS, E.A.*; REDING, D.M.; SCHWARTZ, T.S.; PALACIOS, M.G.; BRONIKOWSKI, A.S.; Gonzaga University; Iowa State University; Iowa State University; CENPAT-CONICAT; Iowa State University addis@gonzaga.edu
Life history theory, and specifically of the pace of life hypothesis, postulates the existence of trade-offs with organisms falling at the “slow” end of the continuum exhibiting low annual reproduction, slow growth and long lifespan while organisms at the “fast” end have higher reproduction, faster growth and shorter lifespans. While the existence of the pace of life continuum has been documented in a myriad of species, from nematodes to mammals, little is know about the physiological mechanisms underlying these demographic and physiological trade-offs. The insulin-like signaling (IIS) pathway is an evolutionarily conserved molecular network that has been is involved in the pace of life trade-offs in model organisms. Key components of the IIS pathway include insulin-like growth factor 1 and 2 (IGF-1, IGF-2) and associated receptors (IGF-1R, IGF-2R). In this study, we explore the role of these components of the IIS pathway in growth of two genetically divergent ecotypes of the western terrestrial garter snake, Thamnophis elegans, which exhibit these slow and fast paces of life. We used a common-garden design in which snakes from each ecotype were placed in one of two daily temperature treatments from birth: 16 hours of voluntary heat exposure with eight hours at 20°C or eight hours of voluntary heat exposure with 16 hours at 20°C. We compare growth rates with plasma levels of IGF-1 and IGF-2 at three time points during rapid juvenile growth and gene expression levels of IGF-1, IGF-2, IGF-1R, and IGF-2R at 1.2 years of age. Lastly, we discuss the relevance of these results in relation to the life history and environmental differences in these divergent ecotypes of the garter snakes.
