In cetaceans, increased body flexibility is associated with increased maneuverability, this affects the animal’s swimming speed and foraging behavior. A more stable body form is associated with fast swimming and wide turns. One factor that affects the flexibility of a cetacean’s body is the structure and interaction of its vertebrae. Differences in vertebral morphology confer different muscular insertion sites and affect mechanical properties of swimming muscles. We studied vertebral morphology in four closely related and partially sympatric dolphin species from the Southern Hemisphere: Commerson’s dolphin (Cephalorhynchus commersonii), Peale’s dolphin (Lagenorhynchus australis), the dusky dolphin (Lagenorhynchus obscurus) and the hourglass dolphin (Lagenorhynchus cruciger). The former two species are usually considered coastal, associated with complex habitats where foraging strategies require greater maneuverability; they also show plasticity in their prey preferences. The latter two species are considered fast-swimming cooperative feeders, with long distance movements reflecting prey availability in pelagic habitats. We employed three-dimensional (3D) geometric morphometric techniques and multivariate analyses to evaluate differences in vertebral morphology. Our analyses tested whether particular morphologies that limit or enhance flexibility were associated with preferred habitats and feeding strategies. We established links between morphology and behavioral patterns based on the biomechanical significance of specific vertebral morphological features. Principal component analyses (PCA) showed great differentiation between species in all the studied regions along the vertebral column. This was especially evident in the middle area, except in the case of dusky and hourglass dolphins which showed no discernible morphological difference in their mid-column vertebrae. PCA results were supported by statistically significant Mahalanobis distances (MD) between species. Species associated with complex habitats and behaviors possessed morphological features associated with greater flexibility of the column (i.e., spool-shaped vertebrae with short erect processes), whereas cooperative-feeder species possessed features associated with greater stability (i.e., disk-shaped vertebrae with long strongly bent processes). In these closely related and partially sympatric dolphins, vertebral morphology is distinctive and varies with the differential foraging strategies and habitat of each species. These findings reveal morphological plasticity among these dolphin species, highlighting the importance of behavioral complexity and of habitat use in the evolutionary development of morphological adaptations.

中文翻译：

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部分同域海豚的椎骨形态学：一种 3D 方法

在鲸类中，身体灵活性的增加与机动性的增加有关，这会影响动物的游泳速度和觅食行为。更稳定的体型与快速游泳和大转弯有关。影响鲸类身体柔韧性的一个因素是其椎骨的结构和相互作用。椎体形态的差异赋予不同的肌肉插入部位并影响游泳肌肉的机械性能。我们研究了来自南半球的四种密切相关且部分同域的海豚物种的椎骨形态：康姆森海豚 (Cephalorhynchus commersonii)、皮尔海豚 (Lagenorhynchus australis)、暗色海豚 (Lagenorhynchus obscurus) 和沙漏海豚。前两个物种通常被认为是沿海的，与觅食策略需要更大机动性的复杂栖息地相关；它们在猎物偏好方面也表现出可塑性。后两种物种被认为是快速游泳的合作饲养者，其长距离运动反映了远洋栖息地的猎物可用性。我们采用三维 (3D) 几何形态测量技术和多变量分析来评估椎体形态的差异。我们的分析测试了限制或增强灵活性的特定形态是否与首选栖息地和饲养策略有关。我们根据特定椎体形态特征的生物力学意义建立了形态学和行为模式之间的联系。主成分分析 (PCA) 显示沿脊柱的所有研究区域的物种之间存在很大差异。这在中间区域尤其明显，除了暗纹和沙漏型海豚的中柱椎骨没有明显的形态差异。PCA 结果得到了物种之间具有统计学意义的马氏距离 (MD) 的支持。与复杂栖息地和行为相关的物种具有与柱的更大灵活性相关的形态特征（即，具有短直立过程的线轴状椎骨），而合作饲养物种具有与更大稳定性相关的特征（即，具有长的盘状椎骨）。强烈弯曲的过程）。在这些密切相关且部分同域的海豚中，椎骨形态是独特的，并随着每个物种的不同觅食策略和栖息地而变化。这些发现揭示了这些海豚物种之间的形态可塑性，突出了行为复杂性和栖息地利用在形态适应进化发展中的重要性。