Meeting Abstract

129.5  Tuesday, Jan. 7 14:30  The insulin-like signaling pathway (IIS) as a regulator of life histories in Western terrestrial garter snakes ADDIS, E.A.*; REDING, D.M; SCHWARTZ, T.S.; PALACIOS, M.G.; BRONIKOWSKI, A.S.; Gonzaga University; Luther College; University of Alabama, Birmingham; CENPAT-CONICET; Iowa State University addis@gonzaga.edu

Western terrestrial garter snakes (Thamnophis elegans) living around Eagle Lake, California have evolved two distinct ecotypes, differing in growth, maturation and reproduction rates, lifespan and skin morphology. While these ecotypes nicely conform to life history theory of trade-offs between lifespan and reproductive output, little is known about the underlying mechanisms. Studies in model organisms have hinted at a role of the insulin-like signaling (IIS) pathway in regulating these trade-offs. We raised neonates from birth of both ecotypes under two rearing conditions that differed in thermal availability for 1.4 years. At the end of the rearing period, we tested for differences among four constituents of the IIS pathway in these snakes in response to our 2 x 2 design (ecotype x thermal availability): insulin-like growth factor 1 and 2 (IGF-1 and IGF-2) and associated receptors (IGF-1R and IGF-2R) correlating with growth. We analyzed protein levels of IGF-1 and IGF-2 and mRNA levels of IGF-1, IGF-2, IGF-1R, IGF-2R among the brain, liver, and muscle for significant ecotype, thermal availability and ecotype x thermal availability interactions. The effects of ecotype and treatment varied across tissue types, genes, and protein expression. IGF-1 and IGF-2 mRNA levels were highest in the liver and IGF-1R and IGF-2R mRNA levels were highest in the brain; muscle levels were intermediate. Unexpectedly, both circulating protein and mRNA levels of IGF-2 were higher than those of IGF-1. Birth size (SVL) and sex also affected mRNA and protein levels. In this talk, we will explore the implications of these results.