Transgenerational effects of maternal corticosterone across early life in a viviparous snake

Abstract

Glucocorticoids (GCs) are central mediators of vertebrate responses to intrinsic and extrinsic stimuli. Among the sources of variation in circulating GCs are transgenerational effects mediated by mothers. Here we studied potential maternal effects mediated by GCs on offspring phenotype in a live-bearing reptile, the western terrestrial garter snake (Thamnophis elegans). We evaluated the association between baseline corticosterone (CORT) levels during gestation (i.e., preparturition) in field-captured mothers and 1) reproductive success and offspring sex ratios, 2) birth phenotypic traits of offspring born under common-garden laboratory conditions, and 3) neonate (age 3 months) and juvenile (age 12 months) traits of offspring raised under two thermal regimes (‘warm’ and ‘cool’) during their first year of life. Reproductive success and offspring sex ratios were not associated with preparturition maternal CORT, but pregnant snakes with higher CORT levels gave birth to smaller, lighter offspring, which tended to grow faster to age three months. Neonate baseline CORT varied with preparturition maternal CORT in a sex-specific manner (positive trend for females, negative for males). Maternal CORT effects on offspring phenotype were no longer detectable in juveniles at age one year. Instead, juvenile phenotypes were most influenced by rearing environment, with offspring raised under the cool regime showing higher baseline CORT and slower growth than those raised under warmer conditions. Our findings support the notion that offspring phenotype might be continuously adjusted in response to environmental cues —both pre- and post-natal— and that the strength of maternal CORT effects declines as offspring develop and experience unique environmental challenges. Our results contribute to a growing literature on transgenerational effects of hormones and help to fill a gap in our knowledge of these effects in ectothermic amniotes.