Department of Biosciences, Mokpo National University, Cheonggye, Muan, Jeollanamdo, 58554, South Korea.
Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, South Korea.
Sci Rep. 2023 Mar 14;13(1):4203. doi: 10.1038/s41598-023-31262-y.
Amphibians are famous for their ability to change colours. And a considerable number of studies have investigated the internal and external factors that affect the expression of this phenotypic plasticity. Evidence to date suggests that thermoregulation and camouflage are the main pressures that influence frogs' adaptive colour change responses. However, certain gaps in our knowledge of this phenomenon remain, namely: (i) how do frogs adjust their colour in response to continuously changing external conditions?; (ii) what is the direction of change when two different functions of colour (camouflage and thermoregulation) are in conflict?; (iii) does reflectance in the near-infrared region show thermally adaptive change?; and (iv) is the colour change ability of each frog an individual trait (i.e., consistent within an individual over time)? Using Dryophytes japonicus (Hylidae, Hyla), we performed a series of experiments to answer the above questions. We first showed that frogs' responses to continuously-changing external conditions (i.e., background colour and temperature) were not linear and limited to the range they experience under natural conditions. Second, when a functional conflict existed, camouflage constrained the adaptive response for thermoregulation and vice versa. Third, though both temperature and background colour induced a change in near-infrared reflectance, this change was largely explained by the high correlation between colour (reflectance in the visible spectrum) and near-infrared reflectance. Fourth, within-individual variation in colour change capacity (i.e., the degree of colour change an individual can display) was lower than inter-individual variation, suggesting individuality of colour change capacity; however, we also found that colour change capacity could change gradually with time within individuals. Our results collectively reveal several new aspects of how evolution shapes the colour change process and highlight how variation in external conditions restricts the extent of colour change in treefrogs.
两栖动物以其变色能力而闻名。相当多的研究已经调查了影响这种表型可塑性表达的内部和外部因素。迄今为止的证据表明，体温调节和伪装是影响青蛙适应性变色反应的主要压力。然而，我们对这种现象的某些认识仍然存在差距，即：（i）青蛙如何根据外部条件的不断变化来调整颜色？；（ii）当颜色的两种不同功能（伪装和体温调节）发生冲突时，变化的方向是什么？；（iii）近红外区域的反射率是否显示出热适应性变化？；（iv）每个青蛙的变色能力是否是个体特征（即，在个体内部随时间保持一致）？使用日本树蛙（树蛙科，雨蛙属），我们进行了一系列实验来回答上述问题。我们首先表明，青蛙对不断变化的外部条件（即背景颜色和温度）的反应不是线性的，并且仅限于它们在自然条件下经历的范围。其次，当存在功能冲突时，伪装会限制体温调节的适应性反应，反之亦然。第三，尽管温度和背景颜色都会引起近红外反射率的变化，但这种变化在很大程度上可以用颜色（可见光谱的反射率）和近红外反射率之间的高度相关性来解释。第四，个体内颜色变化能力的变化（即个体可以显示的颜色变化程度）低于个体间的变化，表明颜色变化能力的个体性；然而，我们还发现，颜色变化能力可以在个体内部随时间逐渐变化。我们的研究结果共同揭示了进化塑造变色过程的几个新方面，并强调了外部条件的变化如何限制树蛙的变色程度。
