三种啮齿类动物前肢挖掘效率分析

以甘肃鼢鼠(Myospalax cansus)、棕色田鼠(Lasiopodomys mandarinus)和小鼠(Mus musculus)为对象,对其尺骨、桡骨和肱三头肌结构进行了比较,并通过力学模型,对这三种生活类型鼠类前肢的挖掘效率进行分析。结果显示,甘肃鼢鼠肘关节位置大幅度前移,尺骨鹰嘴特化突出,形成更加省力的骨学杠杆基础,其中甘肃鼢鼠的鹰嘴尺骨比例达0.40;棕色田鼠和小鼠的鹰嘴尺骨比例分别约为0.19和0.18。此外,甘肃鼢鼠提供挖掘动力的肱三头肌近体端长头覆盖整个肩胛骨下缘,外侧头和内侧头覆盖桡神经沟到肱骨肘关节髁附近区域,远体端扁腱附着于尺骨鹰嘴,整块肌肉非常发达,棕色田鼠和小鼠均无此特化现象。说明甘肃鼢鼠前肢结构更加适应地下掘土生活,其挖掘效率远大于棕色田鼠和小鼠。

Analysis of Digging Efficiency of the Forelimbs of Three Rodents

In order to study the adaptive evolution of the fossorial life of rodent, three different phenotypic rodents including typical subterranean rodent Myospalax cansus, semi-subterranean rodent Lasiopodomys mandarinus and surface-dwelling rodent Mus musculus were selected to analysis their digging efficiency in this study. We constructed their digging efficiency through a simple dynamic model by comparing the morphological characters of ulna, radius and triceps brachii which provide the digging impetus. The result demonstrates that the elbow joint of Myospalax cansus shifts forward a lot, and its ulna olecranon especially extrude, which response for forming a more advantageous dynamics lever and contributing to a better digging efficiency than L. mandarinus and Mus musculus. Agree with the results, the olecranon proportion of Myospalax cansus is about 0.4, L. mandarinus and Mus musculus 0.19 and 0.18 respectively. In addition, the long head of the Myospalax cansus's triceps brachii overlays the whole inferior border of the scapula, the lateral head and medial head start from sulcus of radial nerve and almost overlay humerus, and the triceps brachii attaches to ulna olecranon by a tendon. The whole muscle of Myospalax cansus is well developed, which is significantly stronger than L. mandarinus's and Mus musculus's. The results indicated that Myospalax cansus adapts to the fossorial life better because of the specialization of its forelimbs.