Pierce S E, Lamas L P, Pelligand L, Schilling N, Hutchinson J R
Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02139, USA.
Departamento de Clinica, Faculdade de Medicina Veterinária, Universidade de Lisboa, Av. da Universidade Técnica, 1300-345, Lisboa, Portugal.
Integr Org Biol. 2020 May 27;2(1):obaa015. doi: 10.1093/iob/obaa015. eCollection 2020.
Salamanders and newts (urodeles) are often used as a model system to elucidate the evolution of tetrapod locomotion. Studies range from detailed descriptions of musculoskeletal anatomy and segment kinematics, to bone loading mechanics and inferring central pattern generators. A further area of interest has been muscle activity patterns, measured through electromyography (EMG). However, most prior EMG work has primarily focused on muscles of the forelimb or hindlimb in specific species or the axial system in others. Here we present data on forelimb, hindlimb, and epaxial muscle activity patterns in one species, , during steady state walking. The data are calibrated to limb stride cycle events (stance phase, swing phase), allowing direct comparisons to homologous muscle activation patterns recorded for other walking tetrapods (e.g., lizards, alligators, turtles, mammals). Results demonstrate that has similar walking kinematics and muscle activity patterns to other urodele species, but that interspecies variation does exist. In the forelimb, both the and are active for 80% of the forelimb swing phase, while the is active at the swing-stance phase transition and continues through 86% of the stance phase. In the hindlimb, both the and are active for 30% of the hindlimb swing phase, while the is active 65% through the swing phase and remains active for most of the stance phase. With respect to the axial system, both the anterior and posterior display two activation bursts, a pattern consistent with stabilization and rotation of the pectoral and pelvic girdles. In support of previous assertions, comparison of muscle activity timings to other walking tetrapods revealed broad-scale similarities, potentially indicating conservation of some aspects of neuromuscular function across tetrapods. Our data provide the foundation for building and testing dynamic simulations of fire salamander locomotor biomechanics to better understand musculoskeletal function. They could also be applied to future musculoskeletal simulations of extinct species to explore the evolution of tetrapod locomotion across deep-time.
蝾螈和小鲵（有尾目）常被用作阐明四足动物运动进化的模型系统。研究范围从肌肉骨骼解剖学和节段运动学的详细描述，到骨负荷力学以及对中枢模式发生器的推断。另一个感兴趣的领域是通过肌电图（EMG）测量的肌肉活动模式。然而，大多数先前的肌电图研究主要集中在特定物种的前肢或后肢肌肉，或其他物种的轴向系统。在这里，我们展示了一种蝾螈在稳态行走过程中前肢、后肢和轴上肌的肌肉活动模式数据。这些数据根据肢体步幅周期事件（支撑期、摆动期）进行了校准，从而可以直接与其他行走四足动物（如蜥蜴、短吻鳄、海龟、哺乳动物）记录的同源肌肉激活模式进行比较。结果表明，该蝾螈与其他有尾目物种具有相似的行走运动学和肌肉活动模式，但种间差异确实存在。在前肢，肱三头肌长头和肱三头肌外侧头在80%的前肢摆动期活跃，而肱三头肌内侧头在摆动 - 支撑期过渡时活跃，并持续整个支撑期的86%。在后肢，股二头肌长头和股二头肌短头在30%的后肢摆动期活跃，而半腱肌在摆动期的65%活跃，并在大部分支撑期保持活跃。关于轴向系统，前轴上肌和后轴上肌都显示出两个激活爆发，这种模式与肩带和腰带的稳定及旋转一致。为支持先前的论断，将该蝾螈肌肉活动时间与其他行走四足动物进行比较，发现了广泛的相似性，这可能表明四足动物在神经肌肉功能的某些方面具有保守性。我们的数据为构建和测试火蝾螈运动生物力学的动态模拟提供了基础，以便更好地理解肌肉骨骼功能。它们还可应用于未来对已灭绝物种的肌肉骨骼模拟，以探索四足动物运动在漫长时间里的进化。
