Cree Alison, Tyrrell Claudine L, Preest Marion R, Thorburn Dougal, Guillette Louis J
Department of Zoology, University of Otago, Box 56, Dunedin, New Zealand.
Gen Comp Endocrinol. 2003 Dec;134(3):316-29. doi: 10.1016/s0016-6480(03)00282-x.
Hormones in the embryonic environment, including those of the hypothalamo-pituitary-adrenal (HPA) axis, have profound effects on development in eutherian mammals. However, little is known about their effects in reptiles that have independently evolved viviparity. We investigated whether exogenous corticosterone affected embryonic development in the viviparous gecko Hoplodactylus maculatus, and whether pregnant geckos have a corticosterone response to capture and confinement that is suppressed relative to that in non-pregnant (vitellogenic) females and males. Corticosterone implants (5 mg, slow-release) administered to females in mid-pregnancy caused a large elevation of corticosterone in maternal plasma (P<0.001), probable reductions in embryonic growth and development (P=0.069-0.073), developmental abnormalities and eventual abortions. Cool temperature produced similar reductions in embryonic growth and development (P< or =0.036 cf. warm controls), but pregnancies were eventually successful. Despite the potentially harmful effects of elevated plasma corticosterone, pregnant females did not suppress their corticosterone response to capture and confinement relative to vitellogenic females, and both groups of females had higher responses than males. Future research should address whether lower maternal doses of corticosterone produce non-lethal effects on development that could contribute to phenotypic plasticity. Corticosterone implants also led to increased basking in pregnant females (P<0.001), and basal corticosterone in wild geckos (independent of reproductive condition) was positively correlated with body temperature (P<0.001). Interactions between temperature and corticosterone may have broad significance to other terrestrial ectotherms, and body temperature should be considered as a variable influencing plasma corticosterone concentrations in all future studies on reptiles.
胚胎环境中的激素，包括下丘脑 - 垂体 - 肾上腺（HPA）轴的激素，对真兽类哺乳动物的发育具有深远影响。然而，对于它们在独立进化出胎生的爬行动物中的作用却知之甚少。我们研究了外源性皮质酮是否会影响胎生壁虎黄斑肥趾虎的胚胎发育，以及怀孕的壁虎对捕获和禁闭的皮质酮反应是否相对于未怀孕（卵黄生成期）的雌性和雄性受到抑制。在怀孕中期给雌性植入皮质酮（5毫克，缓释）会导致母体血浆中皮质酮大幅升高（P<0.001），可能会使胚胎生长发育减缓（P = 0.069 - 0.073），出现发育异常并最终流产。低温也会使胚胎生长发育出现类似程度的减缓（与温暖对照组相比，P≤0.036），但妊娠最终仍能成功。尽管血浆皮质酮升高具有潜在危害，但怀孕雌性相对于卵黄生成期雌性并未抑制其对捕获和禁闭的皮质酮反应，且两组雌性的反应均高于雄性。未来的研究应探讨较低剂量的母体皮质酮是否会对发育产生非致命影响，从而导致表型可塑性。皮质酮植入还导致怀孕雌性晒太阳增加（P<0.001），野生壁虎的基础皮质酮（与生殖状态无关）与体温呈正相关（P<0.001）。温度和皮质酮之间的相互作用可能对其他陆生变温动物具有广泛意义，在未来所有关于爬行动物的研究中都应将体温视为影响血浆皮质酮浓度的一个变量。
