高原鼢鼠四肢骨的进化适应性分析

通过对比分析了高寒草甸生态系统的高原鼢鼠(Myospalax baileyi)、高原鼠兔(Ochotona curzoniae)及根田鼠(Microtus oeconomus)的四肢骨,结果表明,地下啮齿动物高原鼢鼠的四肢骨比地面种类高原鼠兔和根田鼠的对应骨骼粗壮,显示其较强的挖掘能力。与挖掘效率相关的尺骨挖掘动力臂系数,高原鼢鼠为0.3617,而高原鼠兔和根田鼠不到0.17。高原鼢鼠与其他两物种的四肢骨重量分布也明显不同:高原鼢鼠的前肢骨重量超过后肢骨,而高原鼠兔及根田鼠则正好相反;高原鼠兔及根田鼠的桡尺骨重量在四肢骨中最低,而高原鼢鼠的桡尺骨重量在四肢骨中则最高。这些特征反映了地下啮齿动物为了适应地下生活方式,其四肢骨骼系统已经发生了显著变化,这对于研究地下啮齿动物的进化适应性问题具有重要意义。

Evolutionary Adaptation Analysis on Limb Bones of Myospalax baileyi

The limb bones of Myospalax baileyi,Ochotona curzoniae and Microtus oeconomus were compared.Each of the four limb bones of subterranean M.baileyi including radius-ulna(not concrescenced),humerus,femur and tibiofibula was more thickset than the corresponding limb bone of other two 'up ground' rodent species O.curzoniae and M.oeconomus.It indicated the higher digging ability of M.baileyi.The length of 'power arm index'(from the center of incisura semilunaris to the upper end of ulna)which means,to some degree,the digging efficiency of M.baileyi reached to 0.361 7;while for O.curzoniae and M.oeconomus this value was no more than 0.17.Moreover,the weight of each piece of limb bone significantly differed between subterranean species and up ground species:for M.baileyi,forelimb bones were heavier than the hindlimb bones,and radius-ulna became the heaviest among the four limb bones,while the hind limb bones of O.curzoniae and M.oeconomus were heavier than their fore limb bones.These results evidently indicated that,in order to adapt to the subterranean environment,the subterranean rodent species(at least for M.baileyi)had remarkably modified their limb bone system,which might shed light on our understanding of the evolutionary adaptations of subterranean rodent species.