ACTH-induced stress response during pregnancy in a viviparous gecko: no observed effect on offspring quality

The typical stress response in reptiles involves the release of corticosterone from the adrenal glands. Elevated maternal concentrations of corticosterone in mammals during pregnancy may have deleterious effects on offspring fitness, and recent work has shown a suppression of the hormonal response to stress during pregnancy in rats. Little is known about the influence of reproductive state on the secretion of corticosterone in viviparous reptiles or on the effects of high levels of corticosterone during reproduction on the developing embryos. We examined whether New Zealand common geckos (Hoplodactylus maculatus), pregnant with embryos at stages 34-35 of development, secrete corticosterone in response to adrenocorticotrophic hormone (ACTH) and whether an ACTH-induced increase in maternal corticosterone affects the outcome of pregnancy. Corticosterone concentrations in pregnant lizards increased more than seven-fold over basal levels following injection of ACTH. However, there were no significant effects of elevated corticosterone on the duration or success of pregnancy, or on various morphological measures, growth, or sprint speed of the offspring. This may reflect a lack of sensitivity of relevant embryonic tissues to corticosterone under the conditions of the present experiment or an ability of the embryos to bind, degrade, or restrict placental transport of corticosterone. Future studies should investigate the possibility of corticosteroid effects on other offspring tissues, including effects in adult life.