Maternal aggression is behavior displayed by post-partum lactating female mice toward unfamiliar conspecifics, presumably as a defense against infanticide. A variety of perinatal stressors can impair maternal care in adulthood. Previous studies on associations between developmental perturbations and maternal aggression have produced mixed results. To address this issue, we employed a proxy for developmental instability, fluctuating asymmetry (FA) to further elucidate the relationship between low temperature stress and maternal aggression. FA, small, random deviations from perfect symmetry in bilateral characters is used as a quantitative measure of stress during ontogeny. Dams were either maintained in standard laboratory temperatures (21 ± 2 °C), or cold temperatures (8 ± 2 °C) during gestation. During lactation, their progeny either remained in the temperature condition in which they were gestated or were transferred to the other temperature condition. Four individual measures of FA, a composite of these measures, and three measures of maternal aggression were assessed in the female progeny in adulthood. Exposure to low temperatures during both pre- and early post-natal development increased composite FA and reduced all three measures of maternal aggression compared to controls. Exposure to low temperatures during the pre- or postnatal period alone did not induce either high FA or altered maternal aggression. Certain measures of FA and nest defense were negatively correlated. Our results suggest that low temperatures experienced during gestation and lactation may have important fitness costs. Low maternal aggression towards infanticidal conspecifics is likely to limit the number of offspring surviving into adulthood. Overall, FA appears to be a reliable indicator of chronic developmental stress with implications for fitness.

中文翻译：

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个体发育过程中的低温会增加家鼠（Mus musculus）的波动性不对称性并减少母性攻击性

母性攻击是产后哺乳期雌性小鼠对不熟悉的同种动物表现出的行为，大概是为了防止杀婴。各种围产期压力可能会损害成年期的孕产妇护理。先前关于发育障碍与母亲攻击性之间关联的研究得出了不同的结果。为了解决这个问题，我们采用了发育不稳定性的替代指标——波动不对称性（FA）来进一步阐明低温应激与母体攻击性之间的关系。FA，双侧性状与完美对称性的小而随机的偏差，被用作个体发育过程中压力的定量测量。母鼠在妊娠期间要么维持在标准实验室温度（21±2°C），要么维持在低温（8±2°C）。在哺乳期间，它们的后代要么保持在妊娠时的温度条件下，要么转移到其他温度条件下。在成年雌性后代中评估了 FA 的四项单独测量、这些测量的综合以及母亲攻击性的三项测量。与对照组相比，产前和产后早期发育期间暴露于低温会增加综合 FA 并减少所有三项母亲攻击性指标。仅在产前或产后期间暴露于低温并不会引起高 FA 或母亲攻击性的改变。FA 的某些测量值与巢穴防御呈负相关。我们的研究结果表明，妊娠和哺乳期间经历的低温可能会产生重大的健康成本。母亲对杀婴同种动物的攻击性较低可能会限制存活到成年的后代数量。总体而言，FA 似乎是慢性发育压力的可靠指标，对健康有影响。