繁殖模式由卵生到卵胎生的进化转变是受自然选择驱动的，直接影响物种的繁殖、形态、生理和行为等方面，要求动物在形态和生理上发生相应的变化。因此有鳞类卵生进化研究一直是学术界关注的热点问题。尽管该研究领域已在形态和生理方面开展了大量研究，但这种变化背后潜在的分子机制尚不清楚，迫切需要选取合适的动物模型开展深入研究。本项目拟以三组同属但不同繁殖模式的石龙子为材料，通过实验操纵缩短或延长卵滞留时间，检测各胚胎时期新生卵胚胎时期与卵壳或胚胎膜以及卵黄内钙含量关系，比较同属不同繁殖模式石龙子新生卵胚胎和幼体的干重比，在转录组水平分别比较三组同属不同繁殖模式石龙子在未怀卵、怀卵和产后状态输卵管组织的基因表达差异，筛选与石龙子胚胎钙供应相关的调控基因并进一步比较其在不同时期的表达量变化。研究结果旨在探讨不同繁殖模式石龙子在胚胎不同发育时期钙供应差异及其内在的分子机制，为阐述卵胎生的渐进式进化提供实验证据。

Viviparity is a reproductive mode evolving from oviparity through gradual increases in the length of intrauterine development until parturition. This transition requires dramatic changes to reproductive morphology and physiology, and is among the most fundamental evolutionary transitions. The primary pattern of embryonic nutrition for squamates is lecithotrophy. The evolution of viviparity presents an opportunity for an additional source of embryonic nutrition through delivery of uterine secretions. The assumptions that nutrients for oviparous embryos are mobilized from yolk, and that this source is not disrupted in the transition to viviparity, are supported for most nutrients. In contrast, calcium, an essential nutrient for embryonic development, is mobilized from both yolk and eggshell by oviparous embryos and reduction of eggshell calcium is correlated with viviparity. If embryonic fitness is compromised by disruption of a primary source of calcium, selection may not favor evolution of viviparity, yet viviparity has arisen independently in many squamate lineages. Studies of fetal nutrition in reproductively bimodal species suggest a resolution to this paradox. If uterine calcium secretion occurs during egg retention, calcium placentotrophy evolves prior to viviparity as a replacement for eggshell calcium and embryonic nutrition will not be compromised. This hypothesis is integrated into the current model for evolution of viviparity to address the unique attributes of calcium nutrition. The sequence of events requires a shift in timing of uterine calcium secretion and the embryonic mechanism of calcium retrieval to be responsive to calcium availability. Regulation of uterine calcium secretion and the mechanism of embryonic uptake of calcium are important elements to understanding evolution of viviparity. Although much is known about the morphological and physiological changes involved in reptilian pregnancy, there has been little examination of the underlying genetic mechanism. Nowadays, advances in next-generation transcriptome sequencing allow detailed analysis of gene expression in non-model organisms, which provides the snapshots of nearly all the genes expressed in a tissue and allows direct comparisons of molecular function amongst squamate lineages. Here we will use three pairs of congeneric skinks with different reproductive modes to study calcium dynamics in eggshell and yolk at different embryonic stages. We will compare the transcriptomic data of the uterus tissues from non-pregnant, pregnant and postpartum females to elucidate the molecular mechanisms of calcium provision during pregnancy. This study aims to address questions of regulation of uterine calcium secretion and the mechanism of embryonic uptake of calcium which are important elements to understanding evolution of viviparity, and data generated from this study will provide the clue for the gradual evolutionary transition from oviparity to viviparity in squamate reptiles.