Martin Meg L, Warburton Natalie M, Travouillon Kenny J, Fleming Patricia A
School of Veterinary and Life Sciences, Murdoch University, Murdoch, Western Australia, Australia.
Department of Terrestrial Zoology, Western Australian Museum, Welshpool, Western Australia, Australia.
J Morphol. 2019 Mar;280(3):423-435. doi: 10.1002/jmor.20954. Epub 2019 Feb 1.
Many mammals dig, either during foraging to access subsurface food resources, or in creating burrows for shelter. Digging requires large forces produced by muscles and transmitted to the soil via the skeletal system; thus fossorial mammals tend to have characteristic modifications of the musculoskeletal system that reflect their digging ability. Bandicoots (Marsupialia: Peramelidae) scratch-dig mainly to source food, searching for subterranean food items including invertebrates, seeds, and fungi. They have musculoskeletal features for digging, including shortened, robust forelimb bones, large muscles, and enlarged muscle attachment areas. Here, we compared changes in the ontogenetic development of muscles associated with digging in the Quenda (Isoodon fusciventer). We measured muscle mass (m ), pennation angle, and fiber length (FL) to calculate physiological cross-sectional area (PCSA; a proxy of maximum isometric force) as well as estimate the maximum isometric force (Fmax) for 34 individuals ranging in body size from 124 to 2,390 g. Males grow larger than females in this bandicoot species, however, we found negligible sex differences in mass-specific m , PCSA or FL for our sample. Majority of the forelimb muscles PCSA showed a positive allometric relationship with total body mass, while m and FL in the majority of forelimb muscles showed isometry. Mechanical similarity was tested, and two thirds of forelimb muscles maximum isometric forces (Fmax) scaled with isometry; therefore the forelimb is primarily mechanical similar throughout ontogeny. PCSA showed a significant difference between scaling slopes between main movers in the power stroke, and main movers of the recovery stroke of scratch-digging. This suggests that some forelimb muscles grow with positive allometry, specially these associated with the power stroke of digging. Intraspecific variation in PCSA is rarely considered in the literature, and thus this is an important study quantifying changes in muscle architectural properties with growth in a mammalian model of scratch-digging.
许多哺乳动物都会挖掘，要么是在觅食时获取地下食物资源，要么是为了建造洞穴以供栖身。挖掘需要肌肉产生巨大力量，并通过骨骼系统传递到土壤中；因此，穴居哺乳动物往往具有肌肉骨骼系统的特征性改变，以反映它们的挖掘能力。袋狸（有袋目：袋狸科）主要通过抓挠挖掘来获取食物，寻找包括无脊椎动物、种子和真菌在内的地下食物。它们具有用于挖掘的肌肉骨骼特征，包括缩短、粗壮的前肢骨骼、大块肌肉和扩大的肌肉附着区域。在此，我们比较了南方袋狸（Isoodon fusciventer）与挖掘相关肌肉的个体发育变化。我们测量了肌肉质量（m ）、羽状角和纤维长度（FL），以计算生理横截面积（PCSA；最大等长力的指标），并估计34个体型从124克到2390克的个体的最大等长力（Fmax）。在这个袋狸物种中，雄性比雌性体型更大，然而，我们发现样本中质量特异性的m 、PCSA或FL的性别差异可忽略不计。大多数前肢肌肉的PCSA与总体重呈正异速生长关系，而大多数前肢肌肉的m 和FL呈等速生长。我们测试了机械相似性，三分之二的前肢肌肉最大等长力（Fmax）呈等速生长；因此，前肢在整个个体发育过程中主要是机械相似的。PCSA在抓挠挖掘的动力冲程主要推动者和恢复冲程主要推动者之间的缩放斜率上存在显著差异。这表明一些前肢肌肉以正异速生长，特别是那些与挖掘动力冲程相关的肌肉。文献中很少考虑PCSA的种内变异，因此这是一项重要研究，量化了在抓挠挖掘的哺乳动物模型中肌肉结构特性随生长的变化。
