环境变化对扬子鳄种群性比影响的分子机制

Chinese alligator is a first-class endangered wild animal endemic to China, which possesses about 100 individuals in the wild, and has become the most endangered species of 23 crocodilians in the world. To protect Chinese alligator, Chinese government built a 34.2-hectare wetland reserve in Changxing County of Zhejiang Province and developed an ex-situ protection population. Over the past 30 years, the Changxing ex-situ population has been raised in semi-wild conditions and retains the abilities of natural hunting and reproduction, which help the population expand from the initial 11 founders to current 3117 alligators. However, as the number of Changxing Chinese alligators has increased, the population has gradually exhibited the problem of sex ratio distortion resulted from alterations of living and reproduction conditions from wild to semi-captivity, which greatly hampered population sustainable development. On the other hand, Chinese alligator is a special reptile showing temperature-dependent sex determination (TSD), namely the incubation temperature of the developing embryos decides the sexes, implying that sex ratio of Chinese alligator should be closely related to the temperature. As a result, this project intends to (1) screen TSD-related genes by transcriptome-based differential expression analysis of different stages of embryos, which were obtained from female and male supporting incubtaion temperatures, respectively; (2) construct heat maps of these TSD-related genes under different temperature conditions to identify the temperature-dependant on-off switches for each TSD-related gene; (3) investigate the relation between the temperature of hatching nests and sex ratio of the population; (4) reveal the moleacular mechanism of environmental changes altering sex ratio of Chinese alligator population; (5) finally put forward advice for the managers to correct the distorted sex ratio in order to ensure sustainable development of the Chinese alligator population.

扬子鳄是我国特有的国家一级重点保护的野生动物，野外种群的数量仅100余条，是全球现生的23种鳄类中最为濒危且受到的生存威胁最大的物种。为拯救扬子鳄，我国政府相关部门在浙江省长兴县建立了扬子鳄的人工迁地保护种群。30多年来，扬子鳄在面积约34.2公顷的湿地保护区，始终保持着"自然捕食"和"自然繁育"的野生生活方式，种群的数量已从奠基时的11条扩增至了3117条。然而，随着个体数量的增多，性比失调的问题逐渐凸显出来，并严重阻碍了种群的可持续发展！鉴于扬子鳄是温度决定性别的一类特殊爬行动物，本项目拟以"温度决定性别相关基因的筛选及其开启温度的确认"和"孵化巢环境温度变化与种群性比之间的相关性"为切入点，通过系统深入的研究工作，揭示环境变化对扬子鳄种群性比影响的分子机制这一科学问题，以期为相关部门制定扬子鳄的保护策略提供科学依据。

扬子鳄是我国特有的国家一级重点保护的野生动物，野外种群的数量仅100余条，是全球现生的23种鳄类中最为濒危且受到的生存威胁最大的物种。为拯救扬子鳄，我国政府相关部门在浙江省长兴县建立了扬子鳄的人工迁地保护种群。30多年来，扬子鳄在面积约34.2公顷的湿地保护区，始终保持着"自然捕食"和"自然繁育"的野生生活方式，种群的数量已从奠基时的11条扩增至了3117条。然而，随着个体数量的增多，性比失调的问题逐渐凸显出来，并严重阻碍了种群的可持续发展！鉴于扬子鳄是温度决定性别的一类特殊爬行动物，本项目拟以"温度决定性别相关基因的筛选及其开启温度的确认"和"孵化巢环境温度变化与种群性比之间的相关性"为切入点，通过系统深入的研究工作，揭示环境变化对扬子鳄种群性比影响的分子机制这一科学问题，以期为相关部门制定扬子鳄的保护策略提供科学依据。. 本研究运用组学技术和荧光原位杂交（FISH）方法，从分子水平上（1）证明了扬子鳄是一没有性染色体和雌性默认性别的爬行动物，（2）揭示了扬子鳄温度决定性别的分子机制。通过对27年的繁殖纪录进行统计分析，确认了野生扬子鳄正常的种群性比值为1:4.507，发现孵化巢选址和孵化巢郁闭度是造成扬子鳄种群性比异常的主要环境因子。本项目还利用全自动温湿度检测仪对扬子鳄鳄卵孵化的巢穴进行了整个孵化期的全天候温度监测，并构建了扬子鳄受精卵孵化温度与种群性比之间相关性的函数模型。