How to build your dragon: scaling of muscle architecture from the world's smallest to the world's largest monitor lizard
How to build your dragon: scaling of muscle architecture from the world's smallest to the world's largest monitor lizard
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DOI：
10.1186/s12983-016-0141-5
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发表时间：
2016-02-18
影响因子：
2.8
通讯作者：
Clemente, Christofer J.
中科院分区：
文献类型：
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作者：
Dick, Taylor J. M.;Clemente, Christofer J.
背景资料：骨骼肌的功能设计是由支持和推进之间相互冲突的选择压力塑造的，随着动物的体型变大，这一点变得更加重要。如果较大的动物是较小动物的几何放大版本，则体型的增加将导致肌肉骨骼应力的增加，这是由于与面积相比，质量的比例更大。在大型动物中，这些压力将危险地接近失败点。本文通过对9种蜥蜴27个个体的22块后肢肌肉结构的研究，从7.6 g的短尾巨蜥到40 kg的科莫多巨蜥，提出了一个关于巨蜥肌肉骨骼结构尺度的综合数据集（varanids），提供了有关系统发育的限制和适应的运动肌肉在四足动物蔓延的信息。肌肉质量，pennation和生理横截面积（PCSA）的缩放结果都表明，较大的varanids增加股骨内收肌，膝屈肌和踝跖屈肌的相对力量产生能力，缩放指数大于几何相似性预测。因此，Varanids通过增加肌肉质量和PCSA来减轻与大小相关的压力增加，而不是像其他动物那样采用更直立的姿势。除了肌肉特性与体重的比例效应外，肌肉结构随后肢姿势变化的变化也很突出。在Varanids中，姿势随栖息地偏好而变化。攀爬蜥蜴的姿态是四肢伸展，而陆生蜥蜴的姿态则更为直立。蔓延的物种需要更大的PCSA和肌肉质量在股骨牵开肌，膝屈肌，踝跖屈肌，以支持body.Conclusions：无论是大小和姿势相关的肌肉变化都表明了增加的作用，在支持推进，导致运动性能的下降，以前已被证明与大小的增加。这些估计表明，巨大的更新世蜥蜴（Varanus megalania priscus）可能无法超越与它共同居住在澳大利亚大陆的早期人类。
Background: The functional design of skeletal muscles is shaped by conflicting selective pressures between support and propulsion, which becomes even more important as animals get larger. If larger animals were geometrically scaled up versions of smaller animals, increases in body size would cause an increase in musculoskeletal stress, a result of the greater scaling of mass in comparison to area. In large animals these stresses would come dangerously close to points of failure. By examining the architecture of 22 hindlimb muscles in 27 individuals from 9 species of varanid lizards ranging from the tiny 7.6 g Varanus brevicauda to the giant 40 kg Varanus komodoensis, we present a comprehensive dataset on the scaling of musculoskeletal architecture in monitor lizards (varanids), providing information about the phylogenetic constraints and adaptations of locomotor muscles in sprawling tetrapods.Results: Scaling results for muscle mass, pennation and physiological cross-sectional area (PCSA), all suggest that larger varanids increase the relative force-generating capacity of femur adductors, knee flexors and ankle plantarflexors, with scaling exponents greater than geometric similarity predicts. Thus varanids mitigate the size-related increases in stress by increasing muscle mass and PCSA rather than adopting a more upright posture with size as is shown in other animals. As well as the scaling effects of muscle properties with body mass, the variation in muscle architecture with changes in hindlimb posture were also prominent. Within varanids, posture varies with habitat preference. Climbing lizards display a sprawling posture while terrestrial lizards display a more upright posture. Sprawling species required larger PCSAs and muscle masses in femur retractors, knee flexors, and ankle plantarflexors in order to support the body.Conclusions: Both size and posture-related muscle changes all suggest an increased role in support over propulsion, leading to a decrease in locomotor performance which has previously been shown with increases in size. These estimates suggest the giant Pleistocene varanid lizard (Varanus megalania priscus) would likely not have been able to outrun early humans with which it co-habitated the Australian landmass with.