Department of Life Science, National Taiwan Normal University, Taipei, 116, Taiwan.
Department of Animal Science and Technology, National Taiwan University, Taipei, 106, Taiwan.
Sci Rep. 2018 Oct 30;8(1):16055. doi: 10.1038/s41598-018-34284-z.
Expression of nuptial color is usually energetically costly, and is therefore regarded as an 'honest signal' to reflect mate quality. In order to choose a mate with high quality, both sexes may benefit from the ability to precisely evaluate their mates through optimizing visual systems which is in turn partially regulated by opsin gene modification. However, how terrestrial vertebrates regulate their color vision sensitivity is poorly studied. The green-spotted grass lizard Takydromus viridipunctatus is a sexually dimorphic lizard in which males exhibit prominent green lateral colors in the breeding season. In order to clarify relationships among male coloration, female preference, and chromatic visual sensitivity, we conducted testosterone manipulation with mate choice experiments, and evaluated the change of opsin gene expression from different testosterone treatments and different seasons. The results indicated that males with testosterone supplementation showed a significant increase in nuptial color coverage, and were preferred by females in mate choice experiments. By using quantitative PCR (qPCR), we also found that higher levels of testosterone may lead to an increase in rhodopsin-like 2 (rh2) and a decrease in long-wavelength sensitive (lws) gene expression in males, a pattern which was also observed in wild males undergoing maturation as they approached the breeding season. In contrast, females showed the opposite pattern, with increased lws and decreased rh2 expression in the breeding season. We suggest this alteration may facilitate the ability of male lizards to more effectively evaluate color cues, and also may provide females with the ability to more effectively evaluate the brightness of potential mates. Our findings suggest that both sexes of this chromatically dimorphic lizard regulate their opsin expression seasonally, which might play an important role in the evolution of nuptial coloration.
求偶色的表达通常需要消耗大量能量，因此被视为反映配偶质量的“诚实信号”。为了选择高质量的配偶，雌雄两性都可以通过优化视觉系统来准确评估配偶，而视觉系统的部分调节又受到视蛋白基因修饰的影响。然而，陆地脊椎动物如何调节其颜色视觉敏感性的研究还很少。绿点草蜥（Takydromus viridipunctatus）是一种具有性二态性的蜥蜴，在繁殖季节雄性表现出明显的绿色侧色。为了阐明雄性颜色、雌性偏好和色觉敏感性之间的关系，我们进行了睾酮处理与配偶选择实验，并评估了不同睾酮处理和不同季节对视蛋白基因表达的变化。结果表明，接受睾酮补充的雄性表现出明显增加的求偶色覆盖范围，并在配偶选择实验中受到雌性的偏爱。通过使用定量 PCR（qPCR），我们还发现，较高水平的睾酮可能导致雄性中视蛋白类似物 2（rh2）的增加和长波敏感（lws）基因表达的减少，这种模式也在接近繁殖季节的成熟野生雄性中观察到。相比之下，雌性在繁殖季节表现出相反的模式， lws 增加，rh2 减少。我们认为这种改变可能有助于雄性蜥蜴更有效地评估颜色线索，也可能为雌性提供更有效地评估潜在配偶亮度的能力。我们的研究结果表明，这种具有颜色二态性的蜥蜴的雌雄两性都具有季节性调节视蛋白表达的能力，这可能在求偶色的进化中发挥重要作用。
