Prenatal maternal stress is associated with behavioural and epigenetic changes in Japanese quail.

Prenatal maternal stress (PMS) influences many facets of offspring's phenotype including morphology, behaviour and cognitive abilities. Recent research suggested that PMS also induced epigenetic modifications. In the present study, we analysed, in the Japanese quail, the effects of PMS on the emotional reactivity and cognitive abilities of the F1 offspring. We also investigated in the hippocampus, the paraventricular hypothalamic nucleus and subnuclei of the arcopallium/amygdala the level of two histone post-translational modifications, H3K4me2 and H3K27me3, known to be impacted by stress. We found that PMS does not affect F1 quail's learning abilities but increases their emotional reactivity. Moreover, we demonstrated that PMS induced an increased density of H3K27me3 positive cells, in the hippocampus, paraventricular hypothalamic nucleus and dorsal nucleus of the amygdala, but not variations of H3K4me2. As these brain regions are involved in the control of vertebrates' emotional responses, the effect of PMS on the epigenetic mark H3K27me3 could possibly be a mechanism involved in the behavioural effects we observed in F1 quail.

Mother-chick interactions are affected by chicks' sex and brood composition in Japanese quail.

Sex is a trait which leads mothers to invest asymmetrically in their young, especially in species with a strong dimorphism. Authors usually consider that members of the largest sex require the most investment by mothers. In other cases, mothers care preferentially for members of the sex that increase their fitness, e.g. males, in numerous species. In quail, a precocial bird, mother seems to take more care of their males which are more sensitive to their separation. This study investigates the influence of chicks' sex and brood's sexual composition on the maternal behavior of quail. We evaluated three batches of mothers, composed of (a) unisex broods of males (MM), (b) unisex broods of females (FF), and (c) mixed sex broods (Mx). We recorded mother-chick interactions during 11 days of mothering. We found that MM mothers spent more time warming their chicks and FF mothers were more active. Moreover, females rejected more aggressively and earlier their female chicks than their male chicks. Finally, Mx chicks, whatever their sex, interacted more with their mothers. Our results highlight a greater quantity and quality of maternal care towards male. Mothers invest more in male chicks. We discussed results in terms of each sex's needs.

Maternal care affects chicks' development differently according to sex in quail.

Maternal behavior is known to influence the behavioral development of young. Recently, it was demonstrated that maternal behavior also differed according to sex of chicks and brood sex composition. So, here, we explored if these factors influenced behavioral development of quail chicks when they were brooded, and what characteristics of chicks and foster females could best explain this development. We studied three sets of chick pairs brooded by foster females: unisex male, unisex female, and mixed broods. We found that both emotivity profile and sociality depended on the sex: females were more reactive and less social than males. Females' emotivity profile was correlated with brood composition and foster female activity during maternal care. In males, only sociality was correlated with foster females' scores of aggressive rejection. Our results evidence that male and female chicks respond differentially to maternal behavior. This is discussed in terms of ecological and physiological constraints on development according to sex.

Brood size can influence maternal behaviour and chick's development in precocial birds.

Mothers have a crucial influence on offspring development. Variations of maternal behaviour can be due to numerous parameters, for instance costs are related to the size of a brood/litter, which in turn can influence the level of mothers' investment in each offspring. Here we investigated the influence of brood size on the behaviour of Japanese quail mothers and chicks during the mothering period and on offspring development. We compared two types of broods: small broods of three chicks (N=9) and large broods of six chicks (N=9). Behavioural tests assessed chicks' social and emotional traits. Mothers of large broods emitted more maternal vocalisations at the beginning of the mothering period, but at the end they assumed more non-covering postures and trampled chicks more than mothers of small broods. Chicks in large broods huddled up more whereas chicks in small broods rested alone more frequently. Moreover, the social motivation of chicks in large broods was higher than that of chicks in small broods, although their emotional reactivity levels were similar. Our results evidence the importance of brood size for maintaining family cohesion and the influence of brood size on chicks' interactions with their siblings. We evaluated the influence of mothers and siblings on chicks' behavioural development.