五种鼠的脑和头骨形态及其生态关系

Brain and Skull Morphology in Five Species of Rodents and Their Ecological Relationship

通过测量棕色田鼠 (Microtusmandarinus)、沼泽田鼠 (Microutusfostis)、甘肃鼢鼠 (Myospalaxcan sus)、大仓鼠 (Cricelulustriton)、黑线姬鼠 (Apodomusagraius)的头骨和脑外部形态 ,计算其长度与体长的比值、脑重与体重的比值及其发头化指数。发现棕色田鼠和甘肃鼢鼠的颧宽与体长之比、齿列长与体长之比显著大于大仓鼠和黑线姬鼠 ,这些特征和各自的食物类型紧密相关。棕色田鼠脑颅测量值和体长之比、脑重和体重之比较大 ,甘肃鼢鼠以上值较小。发头化指数由大到小依次为 :棕色田鼠、沼泽田鼠、黑线姬鼠、大仓鼠、甘肃鼢鼠、小白鼠、大白鼠。棕色田鼠脑除嗅球外无性二型 ,而且大脑测量值相对较大。以上脑特征可能和棕色田鼠单配制婚配制度有关。而甘肃鼢鼠大脑较小的原因可能和其多配制婚配制度及其独居生活有关。甘肃鼢鼠和棕色田鼠的小脑测量值与体长之比小于沼泽田鼠、大仓鼠、黑线姬鼠 ;甘肃鼢鼠的视神经很细 ,棕色田鼠视神经较细 ,而其他 3种鼠视神经都较粗 ;甘肃鼢鼠的嗅球较大 ;这些特征与它们分别适应于地下和地上生活方式有关。

Brain and skull measures and brain weights of five species, Microtus mandarinus,M fostis,Myospalax cansus,Cricelulus triton ,and Apodomus agraius were surveyed.Ratios of measurements and body length,ratios of brain weight and body weight,and cephalization index ( k ) were calculated.Ratios of cranium measures and body length (RCM),ratios of brain weight and body weight (RBRW) of Microtus mandarinus are larger than other species.RCM and RBRW of Myospalax cansus are minor.The sequence of k from large to small in five species is Microtus mandarinus,Apodomus agraius,M fostis,Cricelulus triton ,and Myospalax cansus .Having no sexual differences in brain measures and having larger brain in mandarin vole may consist with its monogamous mating system.Smaller brain in Myospalax cansus may be related with its polygamous mating system and solitariness.Ratios of zygomatic width and body length (RZW) and ratios of length of upper molar row and body length (RMRL) in Microtus mandarinus and Myospalax cansus are larger than others.This is because the formers feed on leaves,stalks or roots of plant which consist of more cellulose and Apodomus agraius and Cricelulustriton of the others mainly feed on seeds. Microtus mandarinus and Myospalax cansus have smaller cerebellums,more slender optical nerve and larger olfactory bulbs than Apodomus agraius,M fostis and Cricelulus triton .These maybe relevant to adaptation and evolution of their living underground or on the floor.