Parry Juliet W L, Carleton Karen L, Spady Tyrone, Carboo Aba, Hunt David M, Bowmaker James K
Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom.
Curr Biol. 2005 Oct 11;15(19):1734-9. doi: 10.1016/j.cub.2005.08.010.
Cichlid fish of the East African Rift Lakes are renowned for their diversity and offer a unique opportunity to study adaptive changes in the visual system in rapidly evolving species flocks. Since color plays a significant role in mate choice, differences in visual sensitivities could greatly influence and even drive speciation of cichlids. Lake Malawi cichlids inhabiting rock and sand habitats have significantly different cone spectral sensitivities. By combining microspectrophotometry (MSP) of isolated cones, sequencing of opsin genes, and spectral analysis of recombinant pigments, we have established the cone complements of four species of Malawi cichlids. MSP demonstrated that each of these species predominately expresses three cone pigments, although these differ between species to give three spectrally different cone complements. In addition, rare populations of spectrally distinct cones were found. In total, seven spectral classes were identified. This was confirmed by opsin gene sequencing, expression, and in vitro reconstitution. The genes represent the four major classes of cone opsin genes that diverged early in vertebrate evolution. All four species possess a long-wave-sensitive (LWS), three spectrally distinct green-sensitive (RH2), a blue-sensitive (SWS2A), a violet-sensitive (SWS2B), and an ultraviolet-sensitive (SWS1) opsin. However, African cichlids determine their spectral sensitivity by differential expression of primarily only three of the seven available cone opsin genes. Phylogenetic analysis suggests that all percomorph fish have similar potential.
东非大裂谷湖泊中的丽鱼科鱼类以其多样性而闻名，为研究快速进化的物种群视觉系统的适应性变化提供了独特的机会。由于颜色在配偶选择中起着重要作用，视觉敏感度的差异可能会极大地影响甚至推动丽鱼科鱼类的物种形成。栖息在岩石和沙地栖息地的马拉维湖丽鱼科鱼类具有明显不同的视锥细胞光谱敏感度。通过结合分离视锥细胞的显微分光光度法（MSP）、视蛋白基因测序以及重组色素的光谱分析，我们确定了四种马拉维湖丽鱼科鱼类的视锥细胞组成。MSP表明，这些物种中的每一种主要表达三种视锥色素，尽管不同物种之间存在差异，从而产生三种光谱不同的视锥细胞组成。此外，还发现了光谱不同的视锥细胞的罕见种群。总共鉴定出七个光谱类别。这通过视蛋白基因测序、表达和体外重组得到了证实。这些基因代表了在脊椎动物进化早期就分化的四种主要视锥视蛋白基因类别。所有四个物种都拥有一个长波敏感（LWS）、三种光谱不同的绿敏感（RH2）、一个蓝敏感（SWS2A）、一个紫敏感（SWS2B）和一个紫外敏感（SWS1）视蛋白。然而，非洲丽鱼科鱼类主要通过仅七种可用视锥视蛋白基因中的三种的差异表达来确定其光谱敏感度。系统发育分析表明，所有鲈形目鱼类都具有类似的潜力。
