我国洞穴鱼研究既有一般共性问题也有个性问题。中国特有金线鲃属鱼类是世界上洞穴鱼物种最多的一个属，其洞穴物种中独特的额部隆起、及头背交界处向前突起的“头角”结构是其它洞穴鱼所没有的；曾推测头角可能是正向洞穴适应特征。头部是全身骨骼最复杂之处，包含了丰富的分类与进化信息。由于野外种群小、个体数量少、受标本限制难以常规方法研究，因此不但对金线鲃头角结构所知甚少，而且大多数洞穴物种头部骨骼等都未见报导；这些形态特征对洞穴环境的适应演化研究更有待深入。同步辐射显微CT是新影像技术，具有高空间分辨、高密度分辨率、无损检测等优点，特别适用于珍稀标本。本项目拟以此为主要方法，获取金线鲃头部骨骼三维数字影像，在分子系统发育关系框架下比较不同洞穴物种、以及洞穴和地表物种间头部形态特征，探讨其洞穴适应演化含义。

The diversity and endemicity of Chinese cavefish lead to their distinctive scientific questions. The cyprinid genus Sinocyclocheilus is endemic to China with more than 50 valid species, and almost all of which live in caves for at least part of their life cycles. The troglobitic Sinocyclocheilus species are well-known for their conspicuous morphological modifications in head, such as the upheaval of forehead, and the forward protruding horn-like structure which has been speculated as a potential constructive troglomorphic trait. Head is one of important subjects of the comparative anatomy of teleost, however, there are few reports on the morphology of head skeleton of Sinocyclocheilus cavefish. The limited availability of the rare specimens impedes the investigation of the head morphology using traditional anatomic approach, which in turn retards the study of cave-adaptive traits (troglomorphism) of the cephalic region of Sinocyclocheilus. X-ray microtomography is a non-invasive technique that allows performing high quality three-dimensional rendering and virtual dissection of the subjects without damaging the specimens. This project will employ conventional and synchrotron X-ray microtomography to obtain three-dimensional digital images of cephalic and related regions, and to compare the cephalic skeleton of hypogean and surface species, and to identify their evolutionary pattern (homology versus homoplasy) in the molecular phylogeny context.