俗话说人不可貌相，但有种鱼却喜欢根据外表颜色来选择配偶。研究显示，一个颜色基因的改变足以使一条这种鱼变成“大众情人”或饱受冷遇，这一发现在生物学上具有重要意义。
英国《BMC生物学》杂志29日刊登报告说，日本研究人员对一种鳉鱼进行了实验。这种鱼有多种颜色，其中棕色居多，还有少量的橙色和灰色。观察显示，颜色的不同决定了它们择偶时的不同境遇，橙色鱼较受欢迎，而灰色鱼往往只能找颜色相同的同伴。
研究人员发现，这两种截然不同的境遇实际上只由一个基因决定。这个基因控制着橙色素的数量，如果发生变异，这种鱼可能会变成饱受冷落的灰色。但如果通过人工手段使这个基因过度发挥作用，可培育出具有“超级吸引力”的橙色鱼，它色彩艳丽，广受追捧。这些超级橙色鱼在择偶时也往往互相选择，而对其他鱼视而不见。研究人员认为，如果这种基因变异长期传承下去，将可能导致新物种的形成。
研究人员说，这是第一次发现单个基因可以同时改变生物的第二性征和择偶偏好。过去人们认为生物进化由多个基因相互影响决定，但这一研究表明，也可能存在只有一个基因发生变异，逐渐形成不同物种的情况。（生物谷bioon.com）
生物谷推荐原始出处：
BMC Biology 2009, 7:64doi:10.1186/1741-7007-7-64
Dual control by a single gene of secondary sexual characters and mating preferences in medaka
Shoji Fukamachi , Masato Kinoshita , Kouichi Aizawa , Shoji Oda , Axel Meyer and Hiroshi Mitani
Background
Animals utilize a wide variety of tactics to attract reproductive partners. Behavioral experiments often indicate an important role for visual cues in fish, but their molecular basis remains almost entirely unknown. Studies on model species (such as zebrafish and medaka) allow investigations into this fundamental question in behavioral and evolutionary biology.
Results
Through mate-choice experiences using several laboratory strains of various body colors, we successfully identified one medaka mutant (color interfere; ci) that is distinctly unattractive to reproductive partners. This unattractiveness seems to be due to reduced orange pigment cells (xanthophores) in the skin. The ci strain carries a mutation on the somatolactin alpha (SLa) gene, therefore we expected over-expression of SLa to make medaka hyper-attractive. Indeed, extremely strong mating preferences were detected in a choice between the ci and SLa-transgenic (Actb-SLa:GFP) medaka. Intriguingly, however, the strains showed opposite biases; that is, the mutant and transgenic medaka liked to mate with partners from their own strain, similar to becoming sexually isolated.
Conclusions
This study spotlighted SLa as a novel mate-choice gene in fish. In addition, these results are the first demonstration of a single gene that can pleiotropically and harmoniously change both secondary sexual characters and mating preferences. Although theoretical models have long suggested joint evolution of linked genes on a chromosome, a mutation on a gene-regulatory region (that is, switching on/off of a single gene) might be sufficient to trigger two 'runaway' processes in different directions to promote (sympatric) speciation.
