根田鼠母体捕食应激效应与Trivers-Willard 模型的关系

本研究了根田鼠母体捕食应激对其子代出生、断乳和成体体重、窝性比及死亡率的作用，检验Trivers—Willard模型的2个前提条件、母体应激激素在母体投资中的作用，以及母体捕食应激效应与该模型的关系。将妊娠根田鼠母体暴露于其捕食艾鼬，母体应激子代的出生和断乳体重均显降低；到成体，雄性体重有此效应，而雌性体重则接近对照。出生窝性比无变化，但成体窝性比向雌性偏斜。不同年龄阶段的死亡率无显变化，但累计死亡率明显增大。处理雄性子代在断乳和成体时的皮质酮含量显增高，而雌性子代则无显变化，从而验证了Trivers-Willard模型的2个前提条件，提出应激母体激素参与母体对子代的投资观点，并认为，母体捕食应激使根田鼠子代成体窝性比向雌性偏斜的生理投资符合进化稳定对策。

Effects of Maternal Stress Induced by Predation Risk on Postnatal Body Mass Growth and Sex Ratio in Root Voles (Microtus oeconomus)

Pattern of sex ratio variation and maternal investment in the literature are often inconsistent. This could be due to intra-and inter-species variations in social system and the assumptions of the Trivers-Willard model not fulfilled in some studies. The present study was designed to test the main assumptions underlying Trivers-Willard model and whether the model could be explained the effects of maternal stress on growth and development of offspring and their sex ratio variation at weaning and adulthood in root voles. Pregnant mothers of root voles were exposed to a living steppe for 4 h daily. At birth and weaning, body mass of male and female offspring from stressed mothers were lighter than that of both offspring from unstressed mothers. Among them, female offspring could compensate for early growth disadvantage after weaning when they were allowed to unlimited access to food after weaning, whereas male offspring could maintain lower body mass into adulthood. Difference between treatment and control in birth sexual ratio per litter was not found. But litter sexual ratio in prenatal stressed offspring was strong skewed toward female at adulthood. Differences between males from stressed and unstressed mothers in mortality were also not found at weaning or adulthood. But mortality during from birth to adulthood in parental stressed male offspring was significantly increased compared with the control. We suggest that maternal stressful hormones secreted during gestation take part in sex-biased maternal investments effectively and directly and the consequences of the maternal investments accord with predication of Trivers-Willard mode.