Department of Biological Sciences, Clemson University, Clemson, SC, USA.
School of Veterinary Medicine, University of Georgia, Athens, GA, USA.
J Anat. 2021 Sep;239(3):747-754. doi: 10.1111/joa.13449. Epub 2021 Apr 29.
Locomotor force production imposes strong demands on organismal form. Thus, the evolution of novel locomotor modes is often associated with morphological adaptations that help to meet those demands. In the goby lineage of fishes, most species are marine and use their fused pelvic fins to facilitate station holding in wave-swept environments. However, several groups of gobies have evolved an amphidromous lifecycle, in which larvae develop in the ocean but juveniles migrate to freshwater for their adult phase. In many of these species, the pelvic fins have been co-opted to aid in climbing waterfalls during upstream migrations to adult habitats. During horizontal swimming, forces are produced by axial musculature pulling on the vertebral column. However, during vertical climbing, gravity also exerts forces along the length of the vertebral column. In this study, we searched for novel aspects of vertebral column form that might be associated with the distinctive locomotor strategies of climbing gobies. We predicted that stiffness would vary along the length of the vertebral column due to competing demands for stability of the suction disk anteriorly and flexibility for axial thrust production posteriorly. We also predicted that derived, climbing goby species would require stiffer backbones to aid in vertical thrust production compared to non-climbing species. To test these predictions, we used microcomputed tomography scans to compare vertebral anatomy (centrum length, centrum width, and intervertebral space) along the vertebral column for five gobioid species that differ in climbing ability. Our results support our second prediction, that gobies are more flexible in the posterior portion of the body. However, the main variation in vertebral column form associated with climbing ability was the presence of larger intervertebral spaces in Sicyopterus stimpsoni, a species that uses a distinctive inching behavior to climb. These results build on past kinematic studies of goby climbing performance and lend insights into how the underlying vertebral structure of these fishes may enable their novel locomotion.
运动力的产生对生物体形态提出了强烈的要求。因此，新的运动模式的进化通常与帮助满足这些需求的形态适应有关。在鱼类的虾虎鱼谱系中，大多数物种是海洋生物，它们用融合的臀鳍来帮助它们在波涛汹涌的环境中保持稳定。然而，一些虾虎鱼群体已经进化出了洄游的生命周期，幼虫在海洋中发育，但幼鱼在成年期迁移到淡水。在许多这些物种中，臀鳍已经被用于帮助它们在向上游迁徙到成年栖息地的过程中爬上瀑布。在水平游泳时，力是由轴向肌肉拉动脊椎产生的。然而，在垂直攀爬时，重力也会沿着脊椎的长度施加力。在这项研究中，我们寻找了与攀爬虾虎鱼独特运动策略相关的脊椎形态的新方面。我们预测，由于前部吸盘的稳定性和后部轴向推力产生的灵活性之间的竞争需求，脊椎的刚度会沿其长度变化。我们还预测，与非攀爬物种相比，进化后的攀爬虾虎鱼物种需要更坚硬的骨骼来帮助产生垂直推力。为了验证这些预测，我们使用微计算机断层扫描来比较五种在攀爬能力上不同的虾虎鱼物种的脊椎解剖结构（脊椎体长、脊椎体宽和椎间空间）。我们的研究结果支持了我们的第二个预测，即虾虎鱼的身体后部更灵活。然而，与攀爬能力相关的脊椎形态的主要变化是在 Sicyopterus stimpsoni 中存在更大的椎间空间，该物种使用独特的蠕动行为来攀爬。这些结果建立在过去对虾虎鱼攀爬性能的运动学研究的基础上，并为这些鱼类的潜在脊椎结构如何使它们能够进行新的运动提供了新的见解。
