UMR 7179 CNRS/MNHN, Département Adaptations du Vivant, Bâtiment d'Anatomie Comparée, 55 rue Buffon, 75005 Paris, France.
Centre for Invasion Biology, Stellenbosch University, Stellenbosch, South Africa.
J Exp Biol. 2023 Dec 15;226(24). doi: 10.1242/jeb.246545. Epub 2023 Dec 7.
The physical properties of the environment impose strong selection on organisms and their form-function relationships. In water and on land, selective pressures differ, with water being more viscous and denser than air, and gravity being the most important external force on land for relatively large animals such as vertebrates. These different properties of the environment could drive variation in the design and mechanics of the locomotor system of organisms. Animals that use multiple environments can consequently exhibit locomotion conflicts between the demands imposed by the media, leading to potential trade-offs. Here, we tested for the presence of such locomotor trade-offs depending on the environment (water or land) in a largely aquatic frog, Xenopus laevis. We focused on terrestrial and aquatic exertion capacity (time and distance swum or jumped until exhaustion) and aquatic and terrestrial burst capacity (maximal instantaneous swimming velocity and maximal force jump) given the ecological relevance of these traits. We tested these performance traits for trade-offs, depending on environments (water versus air) and locomotor modes (i.e. exertion and burst performance). Finally, we assessed the contribution of morphological traits to each performance trait. Our data show no trade-offs between the performance traits and between the environments, suggesting that X. laevis is equally good at swimming and jumping thanks to the same underlying morphological specialisations. We did observe, however, that morphological predictors differed depending on the environment, with variation in head shape and forelimb length being good predictors for aquatic locomotion and variation in hindlimb and forelimb segments predicting variation in jumping performance on land.
环境的物理特性对生物及其形态-功能关系施加了强大的选择压力。在水中和陆地上，选择压力不同，水的粘性和密度大于空气，而重力是陆地相对较大的动物（如脊椎动物）最重要的外力。这些环境的不同特性可能会导致生物运动系统的设计和力学发生变化。因此，使用多种环境的动物可能会在媒介施加的需求之间表现出运动冲突，从而导致潜在的权衡。在这里，我们在一种主要生活在水中的青蛙 Xenopus laevis 中测试了环境（水或陆地）对运动的影响是否存在这种权衡。我们关注的是陆地和水中的体力消耗能力（游泳或跳跃直到力竭的时间和距离）和水中和陆地的爆发能力（最大瞬间游泳速度和最大力跳跃），因为这些特征与生态有关。我们根据环境（水与空气）和运动模式（即体力消耗和爆发性能）测试了这些性能特征之间是否存在权衡。最后，我们评估了形态特征对每种性能特征的贡献。我们的数据表明，性能特征之间以及环境之间都没有权衡，这表明 X. laevis 由于具有相同的基础形态特化，因此在游泳和跳跃方面都同样出色。然而，我们确实观察到形态预测因子因环境而异，头部形状和前肢长度的变化是水中运动的良好预测因子，后肢和前肢节段的变化则预测了陆地跳跃性能的变化。
