Mothers front-load their investment to the egg stage when helped in a wild cooperative bird

In many cooperative societies, including our own, helpers assist with the post-natal care of breeders' young, and may thereby benefit the post-natal development of offspring. Here we present evidence of a novel mechanism by which such post-natal helping could also have hitherto unexplored beneficial effects on pre-natal development: by lightening post-natal maternal workloads, helpers may allow mothers to increase their pre-natal investment per offspring. We present the findings of a decade-long study of cooperatively breeding white-browed sparrow weaver, Plocepasser mahali, societies. Within each social group, reproduction is monopolized by a dominant breeding pair, and non-breeding helpers assist with nestling feeding. Using a within-mother reaction norm approach to formally identify maternal plasticity, we demonstrate that when mothers have more female helpers they decrease their own post-natal investment per offspring (feed their nestlings at lower rates) but increase their pre-natal investment per offspring (lay larger eggs, which yield heavier hatchlings). That these plastic maternal responses are predicted by female helper number, and not male helper number, implicates the availability of post-natal helping per se as the likely driver (rather than correlated effects of group size), because female helpers feed nestlings at substantially higher rates than males. We term this novel maternal strategy 'maternal front-loading' and hypothesize that the expected availability of post-natal help allows helped mothers to focus maternal investment on the pre-natal phase, to which helpers cannot contribute directly. Such cryptic maternally mediated helper effects on pre-natal development may markedly complicate attempts to identify and quantify the fitness consequences of helping.

Evaluation of direct and maternal responses in reproduction traits based on different selection strategies for postnatal piglet survival in a selection experiment

Background Postnatal piglet survival is important both in economic and animal welfare terms. It is influenced by the piglet’s own direct genetic effects and by maternal genetic effects of the dam, associated with milk production and mothering abilities. These genetic effects might be correlated, affected by other non-genetic factors and unfavourably associated with other reproduction traits such as litter size, which makes the development of optimal breeding strategies a challenge. To identify the optimum selection strategy for piglet survival, a selection experiment was carried out to compare responses in survival and reproduction traits to selection on only direct, only maternal, or both genetic effects of postnatal survival. The data of the experiment were recorded from outdoor reared pigs, with first- and second-generation sires selected based on their estimated breeding values for maternal and direct effects of postnatal survival of indoor reared offspring, respectively, with the opportunity to identify potential genotype-by-environment interaction. Results A Bayesian multivariate threshold-linear model that was fitted to data on 22,483 piglets resulted in significant (Pr(h2 > 0) = 1.00) estimates of maternal and direct heritabilities between 0.12 and 0.18 for survival traits and between 0.29 and 0.36 for birth weight, respectively. Selection for direct genetic effects resulted in direct and maternal responses in postnatal survival of 1.11% ± 0.17 and − 0.49% ± 0.10, respectively, while selection for maternal genetic effects led to greater direct and maternal responses, of 5.20% ± 0.34 and 1.29% ± 0.20, respectively, in part due to unintentional within-litter selection. Selection for both direct and maternal effects revealed a significant lower direct response (− 1.04% ± 0.12) in comparison to its expected response from single-effect selection, caused by interactions between direct and maternal effects. Conclusions Selection successfully improved post- and perinatal survival and birth weight, which indicates that they are genetically determined and that genotype-by-environment interactions between outdoor (experimental data) and indoor (selection data) housed pigs were not important for these traits. A substantially increased overall (direct plus maternal) response was obtained using selection for maternal versus direct or both direct and maternal effects, suggesting that the maternal genetic effects are the main limiting factor for improving piglet survival on which selection pressure should be emphasized.

Maternal Responses and Adaptive Changes to Environmental Stress via Chronic Nanomaterial Exposure: Differences in Inter and Transgenerational Interclonal Broods of Daphnia magna

There is increasing recognition that environmental nano-biological interactions in model species, and the resulting effects on progeny, are of paramount importance for nanomaterial (NM) risk assessment. In this work, Daphnia magna F0 mothers were exposed to a range of silver and titanium dioxide NMs. The key biological life history traits (survival, growth and reproduction) of the F1 intergenerations, at the first (F1B1), third (F1B3) and fifth (F1B5) broods, were investigated. Furthermore, the F1 germlines of each of the three broods were investigated over 3 more generations (up to 25 days each) in continuous or removed-from NM exposure, to identify how the length of maternal exposure affects the resulting clonal broods. Our results show how daphnids respond to NM-induced stress, and how the maternal effects show trade-offs between growth, reproduction and survivorship. The F1B1 (and following germline) had the shortest F0 maternal exposure times to the NMs, and thus were the most sensitive showing reduced size and reproductive output. The F1B3 generation had a sub-chronic maternal exposure, whereas the F1B5 generation suffered chronic maternal exposure where (in most cases) the most compensatory adaptive effects were displayed in response to the prolonged NM exposure, including enhanced neonate output and reduced gene expression. Transgenerational responses of multiple germlines showed a direct link with maternal exposure time to ‘sub-lethal’ effect concentrations of NMs (identified from standard OECDs acute toxicity tests which chronically presented as lethal) including increased survival and production of males in the F1B3 and G1B5 germlines. This information may help to fine-tune environmental risk assessments of NMs and prediction of their impacts on environmental ecology.

Sculpting Culture: Early Maternal Responsiveness and Child Emotion Regulation – A UK-Italy Comparison

Mother-infant interactions, including culturally specific features, have been found to predict child socio-emotional development (e.g., social communication and emotion regulation (ER)). However, research is lacking on the specific processes involved. We used a cross-cultural, longitudinal design, and a microanalytic coding approach to address this issue. Fifty-two mother-infant dyads were recruited from the UK ( N = 21) and Italy ( N = 31), representing Northern European and Mediterranean cultures, respectively. While these cultures share core features of parent-child relationships, their values about emotional expressiveness differ. We observed face-to-face mother-infant interactions at 2 months (T1), and coded infant socio-emotional behavior and maternal responses. Children were seen again at 2 years (T2), when their ER in the face of frustration, using the Barrier Task, was assessed, and the occurrence of different “mature” strategies (communicative and autonomous) coded. Results revealed common features of interactions at T1 (infant socio-emotional expressions, and maternal positive responses), but also cultural variation in the frequency of different infant cues (more pre-speech in UK infants, more smiles in Italians), and of maternal responses to them. While greater overall maternal responsiveness at T1 predicted more mature ER in general at T2, cultural differences in early responsiveness to specific infant behaviors predicted later group differences in children’s use of particular ER strategies, with UK children using more communicative strategies, and Italians more autonomous. Findings indicate that positive maternal behaviors that are common across cultures (e.g., responsiveness) promote overall successful child emotion regulation, while culturally specific features of interactions are associated with how child socio-emotional outcomes are expressed.

Emotion socialization in mothers with mood disorders: Affective modeling and recollected responses to childhood emotion

Growing evidence suggests that emotion socialization may be disrupted by maternal depression. However, little is known about emotion-related parenting by mothers with bipolar disorder or whether affective modeling in early childhood is linked to young adults’ recollections of emotion socialization practices. The current study investigates emotion socialization by mothers with histories of major depression, bipolar disorder, or no mood disorder. Affective modeling was coded from parent–child interactions in early childhood and maternal responses to negative emotions were recollected by young adult offspring (n = 131, 59.5% female, M age = 22.16, SD = 2.58). Multilevel models revealed that maternal bipolar disorder was associated with more neglecting, punishing, and magnifying responses to children's emotions, whereas maternal major depression was associated with more magnifying responses; links between maternal diagnosis and magnifying responses were robust to covariates. Young adult recollections of maternal responses to emotion were predicted by affective modeling in early childhood, providing preliminary validity evidence for the Emotions as a Child Scale. Findings provide novel evidence that major depression and bipolar disorder are associated with altered emotion socialization and that maternal affective modeling in early childhood prospectively predicts young adults’ recollections of emotion socialization in families with and without mood disorder.

Central Neural Circuits Regulating Maternal Behavior in Nonhuman Mammals

Chapter 5 reviews the brain circuits that regulate maternal behavior in nonhuman mammals. The medial preoptic area (MPOA) is essential for both the onset and maintenance of maternal behavior. Hormones and oxytocin act on the MPOA to stimulate the onset of maternal behavior. The neurotransmitters contained within MPOA neurons that may regulate maternal behavior are described, as are several neural inputs to the MPOA that regulate its output. A defensive neural circuit that inhibits maternal behavior in most virgin female mammals is described. MPOA output stimulates maternal behavior by depressing the defensive circuit while also activating neural circuits that underpin maternal motivation. MPOA output to the mesolimbic dopamine system is essential for appetitive maternal responses, while its output to the periaqueductal gray regulates consummatory responses. Synaptic plasticity within the MPOA-to-mesolimbic DA circuit is involved in the development of an enduring mother–infant bond.

Machine learning reveals adaptive maternal responses to infant distress calls in wild chimpanzees

Distress calls are an acoustically variable group of vocalizations ubiquitous in mammals and other animals. Their presumed function is to recruit help, but it is uncertain whether this is mediated by listeners extracting the nature of the disturbance from calls. To address this, we used machine learning to analyse distress calls produced by wild infant chimpanzees. It enabled us to classify calls and examine them in relation to the external event triggering them and the distance to the intended receiver, the mother. In further steps, we tested whether the acoustic variants produced by infants predicted maternal responses. Our results demonstrated that, although infant chimpanzee distress calls were highly graded, they conveyed information about discrete events, which in turn guided maternal parenting decisions. We discuss these findings in light of one the most vexing problems in communication theory, the evolution of vocal flexibility in the human lineage.