Atkins Natalia, Swain Roy, Jones Susan M
School of Zoology, University of Tasmania, Tasmania, Australia.
J Exp Zool A Ecol Genet Physiol. 2007 Jul 1;307(7):397-405. doi: 10.1002/jez.394.
Niveoscincus microlepidotus, the southern snow skink, is a biennially reproducing alpine viviparous lizard with an extremely protracted gestation period: embryos are fully developed in autumn, but held over winter so that offspring are born in spring. The obvious benefits for offspring survival of delaying birth until spring have been demonstrated previously. To examine the consequences of deferred parturition for offspring characteristics, we compared neonates obtained in autumn by dissection with neonates born naturally in the spring. Our results demonstrate that deferral of parturition until spring represents a trade-off between key offspring characteristics (spring neonates exhibit lower growth rates, reduced sprint speed after birth, reduced condition and decreased energy reserves) and offspring size [spring neonates are heavier (wet mass) and longer (snout-vent length)]. Furthermore, when females are placed into cold experimental conditions in spring around the time of natural parturition, this species is able to defer parturition for an additional 4 weeks with no significant effect on offspring characteristics. Our results provide further evidence that flexibility in birth date provides a significant advantage to viviparous lizards living in cold climates.
南方雪蜥（Niveoscincus microlepidotus）是一种每两年繁殖一次的高山胎生蜥蜴，妊娠期极长：胚胎在秋季完全发育，但会越冬，以便幼崽在春季出生。先前已证明将出生推迟到春季对幼崽生存有明显益处。为了研究延迟分娩对幼崽特征的影响，我们将秋季通过解剖获得的新生幼崽与春季自然出生的新生幼崽进行了比较。我们的结果表明，将分娩推迟到春季代表了关键幼崽特征（春季新生幼崽生长速度较低、出生后短跑速度降低、身体状况下降和能量储备减少）与幼崽大小（春季新生幼崽更重（湿重）且更长（吻肛长度））之间的权衡。此外，当雌性在春季自然分娩前后被置于寒冷的实验条件下时，该物种能够将分娩再推迟4周，而对幼崽特征没有显著影响。我们的结果提供了进一步的证据，表明出生日期的灵活性为生活在寒冷气候中的胎生蜥蜴提供了显著优势。
