Abstract
Attempts to understand the degeneration of the eyes in cave fish has largely been explained by either various extents of gradual degeneration, ranging from partial to total loss, observed in various species or by acceleration of loss caused by dark environments. However, neither the theory of biological evolution developed by Charles Darwin nor the neutral theory of molecular evolution formulated by Kimura Motoo adequately explains these phenomena. Recent trends in utilizing multidisciplinary research, however, have yielded better results, helping reveal a more complex picture of the mechanisms of degeneration. Here, we summarize the current progress of the research via morphology and anatomy, development biology, animal behavior science and molecular genetics, and offer some perspectives on the ongoing research into the development and degeneration of eyes in cave fish.
Highlights
Attempts to understand the degeneration of the eyes in cave fish has largely been explained by either various extents of gradual degeneration, ranging from partial to total loss, observed in various species or by acceleration of loss caused by dark environments
Neither the theory of biological evolution developed by Charles Darwin nor the neutral theory of molecular evolution formulated by Kimura Motoo adequately explains these phenomena
We summarize the current progress of the research via morphology and anatomy, development biology, animal behavior science and molecular genetics, and offer some perspectives on the ongoing research into the development and degeneration of eyes in cave fish
Summary
Attempts to understand the degeneration of the eyes in cave fish has largely been explained by either various extents of gradual degeneration, ranging from partial to total loss, observed in various species or by acceleration of loss caused by dark environments. We summarize the current progress of the research via morphology and anatomy, development biology, animal behavior science and molecular genetics, and offer some perspectives on the ongoing research into the development and degeneration of eyes in cave fish. 生物学领域的早期研究大多是以描述、记录、 归类的方法对实验材料进行外部形态观察及内部 构造解剖开始。在最初洞穴鱼类眼部退化的形态解 剖学研究中, 科学家们借助低倍光学显微镜观察认 为长期在暗环境中生活的这些鱼类的眼部结构高 度退化且视觉和感光功能完全丧失。随着形态解剖 学研究技术的不断进步, 早期的低倍光学显微镜粗 略观察渐渐被高倍光学显微镜、荧光显微镜、相差 显微镜、电子显微镜等精确观察所取代(Yang, 1992), 观察的对象也由表及里, 深入到细胞器的层面(Liu & Zheng, 1997)。借助高倍光学显微镜科学家们揭示 了洞穴鱼眼部构造的真实情况, 虽然洞穴鱼类眼部 被表皮覆盖 , 被脂肪填充 (Nguyen-Legros et al, 1987), 但视网膜仍有残留(Zilles et al, 1983)。随后 的超薄切片显微观察结果指出,洞穴鱼的视网膜中 没有可辨色的视锥细胞, 但可感光的视杆细胞有所 残留(Kos et al, 2001), 这与正常鱼类的视网膜同时 含有视杆和视锥细胞的情况相异 (Li & Tao, 2002)。除依赖残存的视杆细胞进行感光外, 洞穴鱼 还借助松果体中残留的感光细胞对光做出一定反 应。松果体是哺乳动物脑内的一种重要神经内分泌 转换器(Fan et al, 2001)。硬骨鱼的松果体不但具有 内分泌功能, 还具有感光作用, 因此,又被称作顶 眼或者退化的第三只眼(Wang et al, 1994)。通过高倍 光学显微镜的精细观察发现洞穴鱼类的松果体也 存在不同程度的退化, 但显微镜下仍可以分辨出残 存的感光细胞(Besharse & Hollyfield, 1976; McNulty, 1978)。进一步利用电子显微镜对洞穴鱼与地表硬骨 鱼松果体感光细胞的超微形态结构进行解剖比较 发现, 洞穴鱼类松果体中的感光细胞外节的结构与 地表生活的硬骨鱼存在明显区别 (Herwig, 1976; Kos & Bulog, 2000)。除了眼部构造的变化, 洞穴鱼 类颅面中与眼部相关联的一些骨骼结构, 如围眶骨 系也发生了 改变而异于 地表的硬骨 鱼类(Jeffery, 2008; Yamamoto et al, 2003)。然而, 无论是最初通过 光学显微镜看到洞穴鱼退化的眼部被膜覆盖, 还是 后期通过电子显微镜揭示洞穴鱼退化眼部的细胞 组成异常, 以及与眼部感光有关联的嗅球细胞比地 表普通鱼类增多等现象, 都是洞穴鱼类眼部退化的 表象观察结果, 尚属于定性的形态解剖研究。近几 年, 形态解剖学发展出一种全新的形态计量术。该 技术运用数学原理, 利用图像分析仪对生物组织和 细胞进行二维或三维的形态学测量, 从而使得形态 解剖学研究由定性阶段发展到了定量阶段 (Peng, 2009)。形态计量等定量型的新技术的运用必将推动 洞穴鱼类眼部退化的形态解剖学研究向更科学、更 精准的方向发展。 Developmental mechanisms for retinal degeneration in the blind cavefish Astyanax mexicanus [J].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
