Low temperatures during ontogeny increase fluctuating asymmetry and reduce maternal aggression in the house mouse, Mus musculus

Abstract

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.

A subpopulation of embryonic microglia respond to maternal stress and influence nearby neural progenitors

“…We chose cold stress as a physiologically relevant model since the hypothalamus plays a prominent role in thermoregulation (Bachtell et al, 2003;Kasahara et al, 2013;Laperrousaz et al, 2018) and cold exposure has been shown to elevate corticosterone levels and alter microglial physiology in adult mice (Xu et al, 2019). Moreover, cold exposure during the pre-and/or postnatal period can impact aggressive behaviors controlled by hypothalamic circuits (Benderlioglu and Dow, 2017;Hohmann et al, 2013), suggesting that cold stress can alter hypothalamic development and function.…”

“…The hypothalamus is essential for maintaining homeostatic processes, such as fluid-balance, body temperature, energy regulation, metabolism, physical activity, diurnal activity, reproduction, parturition, and lactation (Berthoud, 2002;Hill et al, 2008;Li et al, 1998;Nesan and Kurrasch, 2016;van Dijk et al, 2011). Less appreciated but equally important, the hypothalamus also influences emotional outputs, such as aggression and defensiveness, as well as other social behaviors (Bandler et al, 2000;Benderlioglu and Dow, 2017;Hohmann et al, 2013). The release of trophic hormones, which serve to connect the nervous system to the peripheral endocrine system, enables the hypothalamus to regulate homeostasis, and this is especially true for stress (F€ uzesi et al, 2016;Kim et al, 2019).…”