Towe A L, Mann M D
Department of Physiology and Biophysics, University of Washington, School of Medicine, Seattle, USA.
J Hirnforsch. 1995;36(2):195-201.
Cranial capacities were measured in two sets of genetically-related pocket gophers, one from desert shrubland, the other from an irrigated alfalfa field. The two sets differed in sex ratio and in age structure, but both showed the strong sexual dimorphism characteristic of pocket gophers. After sorting by trapping site, sex and suture score (age), the covariations between brain weight, body length and cranial basilar length were calculated. The brains of the alfalfa field animals followed the same somatic scaling relations as those of the desert shrubland animals, all the differences in brain weight being explained fully by the sexual dimorphism in the somatic variables. The slopes defined by the means of brain and body weights of females and of males from the two sites were nearly equal, and were the same as the trajectories calculated from a geometric model based on the statistical characteristics of the samples. It is argued that these slopes define how much brain size must increase to serve a body of increased size, with no change in life style. The differences in age structure between males from the two sites provided evidence of a mechanism by which sexual dimorphism might develop and be enhanced in a nutritionally-enriched environment.
对两组具有遗传关系的囊鼠的脑容量进行了测量，一组来自沙漠灌木丛地区，另一组来自灌溉苜蓿地。这两组在性别比例和年龄结构上有所不同，但都表现出囊鼠特有的强烈两性异形特征。按捕获地点、性别和缝合线评分（年龄）进行分类后，计算了脑重、体长和颅底长度之间的协变关系。苜蓿地囊鼠的大脑与沙漠灌木丛地区囊鼠的大脑遵循相同的身体比例缩放关系，脑重的所有差异都完全由身体变量中的两性异形来解释。来自两个地点的雌性和雄性的脑重与体重平均值所确定的斜率几乎相等，并且与根据样本统计特征从几何模型计算出的轨迹相同。有人认为，这些斜率确定了在生活方式不变的情况下，身体尺寸增加时脑容量必须增加多少。两个地点雄性的年龄结构差异提供了一种机制的证据，通过这种机制，两性异形可能在营养丰富的环境中发展并得到增强。
