Maternal corticosterone increases thermal sensitivity of heart rate in lizard embryos

While it is well-established that maternal stress hormones, such as corticosterone (CORT), can induce transgenerational phenotypic plasticity, few studies have addressed the influence of maternal CORT on pre-natal life stages. We tested the hypothesis that experimentally increased CORT levels of gravid female eastern fence lizards (Sceloporus undulatus) would alter within-egg embryonic phenotype, particularly heart rates. We found that embryos from CORT-treated females had heart rates that increased faster with increasing temperature, resulting in higher heart rates at developmentally-relevant temperatures but similar heart rates at maintenance-relevant temperatures, compared to embryos of control mothers. Thus, maternal CORT appears to alter the physiology of pre-natal offspring, which may speed development and decrease the amount of time spent in eggs; the most vulnerable stage of life.