Abstract: Both visceral organ mass and digestive tract length show phenotypic plasticity in small mammals,which in turn
is related to their living environmental conditions. To further understand the seasonal adaptive strategy for wild Mongolian gerbils (Meriones unguiculatus),we measured the sexual and seasonal variations of the body mass,masses of visceral organs and digestive organs,as well as the length of each portion of the gut from July 2004 to May 2005 at Taipusiqi County, Nei Mongol,China. All specimens were measured 1 - 3 days after they were live-trapped. Both body mass and body length for male gerbils were higher than those of females,but average liver mass for male gerbils was lower than that of females, and no sexual variation was found for other organ masses. For both the sexes,body mass and heart mass was highest in winter, and lowest in summer. For male gerbils,liver mass was higher in summer,and lowest in spring and winter,but no seasonal variation was found in female gerbils. The average testes mass was highest in spring. The mass of both the caecum and small intestine was higher in autumn than in spring,but no seasonal differences were found among other seasons. Average mass of both the stomach and large intestine did not show any seasonal variation. The length of small intestine was longest in winter and shortest in summer. The length of the caecum was shortest in spring,and the length of the arge intestine was longest in spring and shortest in summer. The plastic variations of body mass,and the respective masses of heart,digestive organs and other visceral organs,as well as the lengths of digestive organs,may play important roles in the adaptation of Mongolian gerbils to changing environments.

Key words: Digestive tract, GendeSeasonr, Internal organ, Mongolian gerbils (Meriones unguiculatus), Phenotypic plasticity, Season

摘要： 小哺乳动物内脏器官的重量和消化道的长度具有可塑性,与其所处的环境密切相关。为进一步了解长爪
沙鼠对季节性环境的适应,比较了活捕于内蒙古太仆寺旗的长爪沙鼠的体重、内脏器官的重量及肠道各段长度
的性别和季节变化。结果显示:除体重和体长雄鼠高于雌鼠,肝脏的湿重低于雌鼠外,其他指标均未检测到性
别差异。雌雄鼠的体重和心脏的湿重都在冬季最高,夏季最低;雄鼠肝脏的湿重夏季最高,春季和冬季最低,
雌鼠无季节性变化。睾丸的湿重在春季最高。盲肠和小肠的湿重秋季高于春季,胃和大肠的湿重无季节性差异。
小肠的长度冬季最长,夏季最短;盲肠春季最短,大肠春季最长,夏季最短。体重、心脏、消化器官和其他内
脏器官的重量,以及消化器官长度的可塑性变化等对于长爪沙鼠适应环境具有重要的意义。

关键词: 内脏器官, 消化道, 表型可塑性, 性别, 季节, 长爪沙鼠