Significance of the succession and/or the disappearance of ultraviolet photosensitivity in the Antarctic fish suborder Notothenioidei

本研究旨在探讨硬骨鱼紫外光敏性演替和/或消失的机制。本文以南极海域特有进化的南极鱼类Notothenioidei亚目为研究对象，分析了其视网膜中紫外光视蛋白基因和紫外光视锥细胞的组织学存在。1)紫外锥在更多的地方性家系中存在。在7科棘球蝇科中，有紫外线锥的种与无紫外线锥的种混种。此外，南极最特化的渠道鱼类物种失去了紫外线视锥细胞。因此，推测uv锥是该亚目在物种形成过程中丢失的一个特征。2)紫外视蛋白基因全长1008bp，编码336个氨基酸。对3科9种紫外光视蛋白基因的系统发育分析表明，紫外光视蛋白基因可能与南极鱼的种形成相对应。3)在Channichthyidae Champsocephalus gunnari幼鱼的视网膜中发现了uv锥，并分离到了uv视蛋白基因。因此，在通道鱼中，即使成年鱼缺乏UV-cone，幼鱼也有UV-cone并在其视网膜中表达UV-opsin mRNA。4)蓝视蛋白、绿视蛋白和红视蛋白基因长度分别为1056、1056和1068bp，编码352和356个氨基酸残基。与其他硬骨鱼基因相比，蓝色视蛋白和绿色视蛋白的同源性较低。这可能表明鱼类在适应其栖息地深度或位置的光环境中进化，然后物种特异性地进化出蓝色和绿色视蛋白基因

This study aimed to investigate mechanism of the succession and/or the disappearance of ultraviolet photosensitivity in the teleosts. To achieve this aim, Antarctic fishes suborder Notothenioidei, which accomplished evolution in Antarctic sea endemically, were used for analyzing ultraviolet opsin gene and histological presence of UV-photoreceptor(UV-cone) in their retina.1) The UV-cone presented in more endemic 6 families. In the 7th family Bthydraconidae, speceis having UV-cone and not-having were intermingled. Further, the channichthyid species which are most specialized in Antarctica lost UV-cones. Therefore, it was guessed that the UV-cone is a character being lost during the process of speciation in this suborder.2)The full length UV-opsin gene was 1008bp and encoded 336 amino acids. Phylogenetic analysis of UV-opsin genes among 9 species in 3 families expressed a possibility it correspond to speciation of nototheniid species.3)In the retina of juvenile Champsocephalus gunnari belonging to Channichthyidae, the UV-cone presented and UV-opsin gene was isolated. Therefore, in channichthyiids, it was supposed that even if UV-cone was lack in adult fish, the juvenile fish have the UV-cone and express UV-opsin mRNA in their retina.4)The blue-, green- and red-opsin gene was 1056, 1056 and 1068bp and encoded 352 and 356 amino acid residues, respectively. Lower homology was shown for blue- and green-opsins than red-opsin between other teleost genes. This may indicate that fish evolved adaptively in light environment of their habitat depth or place, and then evolved blue- and green-opsin genes species-specifically