Department of Biological Sciences, DePaul University, Chicago, Illinois, United States of America.
PLoS One. 2019 Jul 29;14(7):e0219677. doi: 10.1371/journal.pone.0219677. eCollection 2019.
Environmental changes can modify the phenotypic characteristics of populations, which in turn can influence their evolutionary trajectories. In ectotherms like fishes, temperature is a particularly important environmental variable that is known to have significant impacts on the phenotype. Here, we raised specimens of the surface ecomorph of Astyanax mexicanus at temperatures of 20°C, 23°C, 25°C, and 28°C to examine how temperature influenced vertebral number and body shape. To increase biological realism, specimens were also subjected to two water turbulence regimes. Vertebral number was counted from x-rays and body shape variation was analysed using geometric morphometric methods. Temperature significantly impacted mean total vertebral number, which increased at the lowest and highest temperatures. Fish reared at lower temperatures had relatively more precaudal vertebrae while fish reared at higher temperatures had relatively more caudal vertebrae. Vertebral anomalies, especially vertebral fusions, were most frequent at the extreme temperature treatments. Temperature significantly impacted body shape as well, with fish reared at 20°C being particularly divergent. Water turbulence also impacted body shape in a generally predictable manner, with specimens reared in high turbulence environments being more streamlined and having extended dorsal and anal fin bases. Variation in environmental variables thus resulted in significant changes in morphological traits known to impact fish fitness, indicating that A. mexicanus has the capacity to exhibit a range of phenotypic plasticity when challenged by environmental change. Understanding the biochemical mechanisms underlying this plasticity and whether adaptive plasticity has influenced the evolutionary radiation of the Characidae, are major directions for future research.
环境变化可以改变种群的表型特征，进而影响它们的进化轨迹。在像鱼类这样的变温动物中，温度是一个特别重要的环境变量，已知它对表型有重大影响。在这里，我们将 Astyanax mexicanus 的表面生态型标本在 20°C、23°C、25°C 和 28°C 的温度下进行饲养，以研究温度如何影响椎骨数量和体型。为了增加生物学的真实性，标本还受到两种水湍流状态的影响。通过 X 射线对椎骨数量进行计数，并使用几何形态测量方法分析体型变化。温度显著影响平均总椎骨数量，最低和最高温度下数量增加。在较低温度下饲养的鱼类具有相对较多的前躯椎骨，而在较高温度下饲养的鱼类具有相对较多的尾椎骨。在极端温度处理下，椎骨异常，尤其是椎骨融合，最为常见。温度也显著影响体型，在 20°C 下饲养的鱼类体型特别不同。水湍流也以一种可预测的方式影响体型，在高湍流环境中饲养的标本更具流线型，并且延长了背鳍和臀鳍的基部。因此，环境变量的变化导致了形态特征的显著变化，这些特征已知会影响鱼类的适应性，这表明 A. mexicanus 在面临环境变化时具有表现出一系列表型可塑性的能力。了解这种可塑性的生化机制，以及适应性可塑性是否影响了 Characidae 的进化辐射，是未来研究的主要方向。
