蓝光诱导近海硬骨鱼类黑色隐蔽伪装色形成的机理

Countershading is a method of camouflage with a vertical luminance gradient from a dark back to a light belly, is perhaps the most common coloration phenotype in the animal kingdom. In bony fishes, countershading plays an important role in social events, such as predator avoidance and prey capture. Countershading is a type of morphological color patterns, where the areas that are typically exposed to more light are darker with more melanophores in bony fishes. So far, how light help animals to develop countershading is still unclear. In a previous study, we found the formation of melanophores-determined dorso-ventral countershading induced by blue light during the development of Paralichthys olivaceus, a marine benthic bony fish. Since blue light from sea surface can reach to over 200 meter depth, the formation of melanophores-determined countershading in various kinds of bony fishes living in offshore might be induced by blue light. In order to better understand the mechanism of countershading development in marine bony fishes, in this research program, we will investigate the morphological feature of melanophores-determined countershading in common marine bony fishes in China, and propose a hypothesis of “Bluelight- 9cRA-ASIP1” to explain how blue light induces the development of countershading, and test the hypothesis in this research using blue light and various means of genetic interference. The research will uncover the key downstream signals of blue light regulation in development of melanophores-determined dorso-ventral countershading. Moreover, we hope can better understand the evolutionary mechanism of countershading in various kinds of marine bony fishes.

鱼体背部体色深、腹部体色浅，是一种伪装色，称为隐蔽伪装色，对于鱼类的避敌和摄食十分重要。对于鱼类隐蔽伪装色的形成，目前尚缺乏深入的研究。硬骨鱼类的隐蔽伪装色，以背、腹部黑色素细胞多寡呈现的黑色隐蔽伪装色最为普遍。我们发现一种近海底层硬骨鱼类的黑色隐蔽伪装色形成，受蓝光的诱导，由于海面蓝光能渗透到近海各种深度，近海硬骨鱼类黑色隐蔽伪装色的形成可能普遍受蓝光的诱导，因此，深入研究蓝光诱导黑色隐蔽伪装色形成的机理，十分重要。本项目提出了蓝光诱导黑色隐蔽伪装色形成的“蓝光-视黄酸-ASIP1”假说，解释来自海面透射下来的蓝光，如何影响鱼体背、腹部黑色素细胞数量形成的差异，并借助各种技术手段验证，明确“蓝光-视黄酸-ASIP1”调控机制在近海硬骨鱼类黑色隐蔽伪装色形成中的作用，进而在分子层面探究近海硬骨鱼类黑色隐蔽伪装色形成的适应进化机制，以更好地理解其在避敌和摄食方面的重要作用。

通过本项目的开展，明确了“蓝光-视黄酸-ASIP1机制”在斑马鱼黑色隐蔽伪装色形成发挥作用，发现蓝光依赖SWS2调控Raldh2合成视黄酸，诱导黑色素细胞形成，并影响asip1基因的背腹部表达分布；发现蓝光之外，紫光和红光也能通过诱导合成视黄酸调控斑马鱼黑色素细胞形成，紫外诱导视黄酸合成酶基因raldh2的表达，而红光则是通过诱导视黄酸合成酶基因raldh3表达而合成视黄酸，表明不同光线诱导黑色素细胞形成的分子机制存在一定的差异；此外，发现SWS2介导蓝光抑制黄色素细胞的形成，SWS1介导紫光诱导斑马鱼虹彩细胞的形成而抑制黄色素细胞的形成，而红光则不会影响黄色素细胞和虹彩细胞的形成，这些发现加深了人们对光线如何影响体色形成的认识；首次调查了中国近海常见上层鱼类和底层鱼类的隐蔽伪装色程度，发现隐蔽伪装色程度主要基于黑色素细胞和黄色素细胞的数量差异，为深入研究鱼类隐蔽伪装色形成明确了方向；调查了“蓝光-视黄酸-ASIP1”机制在近海硬骨鱼类黑色隐蔽伪装色形成的普适性,发现近海硬骨鱼类黑色隐蔽伪装色形成过程中，除了蓝光以外，还存在其它光线调控视黄酸合成，通过影响POMC/MC1R或ASIP1的机制；此外，基于“光线-视黄酸”诱导黑色素细胞形成的机制，对养殖鲆鲽鱼类体色异常进行了遗传与环境互作的理论解释，建立了预防体色异常的技术应用养殖实践，并加以推广应用，有力服务了鲆鲽鱼类的养殖业。

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