石龙子尾部褪色进化驱动力及其行为应性研究

Biological explanation on bright body coloration in animals and its evolutionary force have long attracted the attention of the biologists and evolutionary ecologists. The evolutionary mechanisms of animals’ body color have been hot topics and severe debatable issues for decades. Conspicuous colors in juvenile tails, then fade during maturation are widespread in genus Plestiodon. But we recently found that the blue tail of Chinese four-lined skink (Plestiodon quadrilineatus) is still retained until the maturation, which is different to other skinks in the genus Plestiodon. Based on the previous observation on the significant different ontogenetic changes in tail color of skink, we try to answer the following questions: How do the ontogenetic changes in tail color pass between generations? What do the females mating with males having bright coloration will benefit from? Why do two species with closed genetic relationship adopt different behavioral strategy, and which factors drive its evolution on ontogenetic changes in tail color? In this project, we will select Blue tail skink (P. elegans) and Chinese four-lined skink (P. quadrilineatus) as the study animals: 1) to investigate the mechanisms of blue color production and maintenance by the methods of microtomy and microexamination. 2) to provide a quickly, accurate, and non-invasive method for color quantification using of digital cameras and fiber spectrometer, then promote its potential application on the related color researches in the reptiles. 3) to investigate the relationship between lipid content, predation pressure and tail color in two control experiments, find out the factors influencing the ontogenetic changes in tail color, and test the hypotheses that “the functions of predation pressure and energy storage are evolutionary forces to the ontogenetic changes in tail color in Plestiodon” .

动物鲜艳体色的生物学意义及其进化驱动力，一直以来都是进化生物学研究中的热点问题。前期观察发现石龙子幼体阶段都有着明亮的蓝色尾部，但成体后多数石龙子尾部的蓝色会褪去，但四线石龙子成体后继续保留蓝色尾部。蓝色尾部带来的高适合度表现在哪些方面呢？为什么同属亲缘关系相近的两个物种在尾部褪色过程中采取不同的行为对策，内在的调控机制及其行为适应性是什么？本项目选取蓝尾石龙子和四线石龙子作为研究对象：1）通过切片和扫描电镜方法，解释石龙子尾部的成色原理；2）通过数码拍照和光纤光谱法对尾部颜色进行定量，尝试找出一种快速，准确，非损伤的体色定量方法，推动颜色定量技术在爬行动物行为学中的应用；3）通过行为控制实验探讨石龙子尾部色彩褪色、能量分配和捕食风险之间的关系，并验证假说“尾部能量储存的比重和捕食风险是同属物种在尾部褪色上采取不同行为对策的进化驱动力”。

石龙子属的物种幼体时期都有着明亮的蓝色尾部，成体后多数石龙子尾部的蓝色会褪去，但四线石龙子成体后继续保留蓝色尾部。为了了解其尾部成色机制，我们通过扫描电镜发现黄色和蓝色的尾部真皮层中黑色素和黄色素细胞密度存在差异，此外由虹彩细胞形成光栅结构的厚度和长度也会造成光的折射率发生改变，因此石龙子尾部的色彩是由真皮层中的光栅结构和色素细胞共同形成的混合色。此外，我们通过数码拍照和光纤光谱法对尾部色彩进行了定量，发现光源种类和入射角度会影响色彩定量的准确性，在入射角度45°D65光源时两种方法在色彩定量上具有较好的一致性。最后我们通过行为控制实验证实两种石龙子成体后都存在两性异性现象，但发育周期和生长速度上存在明显差异。因此认为在生长和繁殖上采取不同的对策，权衡能量获取，风险躲避，以及繁殖投入是造成两种石龙子行为差异的原因，进而导致两性异性和尾部褪色差异。