Idiosyncratic gesture use in a mother-infant dyad in chimpanzees (Pan troglodytes schweinfurthii) in the wild.

One promising method to tackle the question, "In which modality did language evolve?" is by studying the ontogenetic trajectory of signals in human's closest living relatives, including chimpanzees (Pan troglodytes). Concerning gestures, current debates centre on four different hypotheses: "phylogenetic ritualization", "social transmission through imitation", "ontogenetic ritualization", and "social negotiation". These differ in their predictions regarding idiosyncratic gestures, making such occurrences a crucial area of investigation. Here, we describe a novel and potential idiosyncratic behaviour - 'hand-on-eye' - which was initially observed in one mother-infant dyad in a community of chimpanzees living in the wild. We systematically investigated the form, sequential organisation, intentionality, usage, function, and distribution of the behaviour over a five-year period. The results showed that 'hand-on-eye' was nearly exclusively deployed in a single mother-infant dyad, was accompanied by hallmarks of intentionality, and served to initiate or resume joint dorsal travel. Although the behaviour was observed once in each of three other mother-infant dyads, these lacked the same frequency and hallmarks of intentionality. 'Hand-on-eye' thus qualifies as an idiosyncratic gesture. The proposed developmental pathway gives support to both the "ontogenetic ritualization" and "social negotiation" hypotheses. It also stresses the crucial need for longitudinal approaches to tackle developmental processes that are triggered by unique circumstances and unfold over relatively long time windows.

Sensitive infant care tunes a frontotemporal interbrain network in adolescence.

Caregiving plays a critical role in children's cognitive, emotional, and psychological well-being. In the current longitudinal study, we investigated the enduring effects of early maternal behavior on processes of interbrain synchrony in adolescence. Mother-infant naturalistic interactions were filmed when infants were 3-4 months old and interactions were coded for maternal sensitivity and intrusiveness with the Coding Interactive Behavior Manual. In early adolescence (Mean = 12.30, SD = 1.25), mother-adolescent interbrain synchrony was measured using hyperscanning EEG during a naturalistic interaction of positive valence. Guided by previous hyperscanning studies, we focused on interbrain connections within the right frontotemporal interbrain network. Results indicate that maternal sensitivity in early infancy was longitudinally associated with neural synchrony in the right interbrain frontotemporal network. Post-hoc comparisons highlighted enhancement of mother-adolescent frontal-frontal connectivity, a connection that has been implicated in parent-child social communication. In contrast, maternal intrusiveness in infancy was linked with attenuation of interbrain synchrony in the right interbrain frontotemporal network. Sensitivity and intrusiveness are key maternal social orientations that have shown to be individually stable in the mother-child relationship from infancy to adulthood and foreshadow children's positive and negative social-emotional outcomes, respectively. Our findings are the first to demonstrate that these two maternal orientations play a role in enhancing or attenuating the child's interbrain frontotemporal network, which sustains social communication and affiliation. Results suggest that the reported long-term impact of maternal sensitivity and intrusiveness may relate, in part, to its effects on tuning the child's brain to sociality.

Influences of quality of maternal care and environmental enrichment on associative memory function in rats with early life lead exposure.

INTRODUCTION: Children in low socioeconomic status (SES) communities are at higher risk of exposure to lead (Pb) and potentially more severe adverse outcomes from Pb exposures. While the factors encompassing SES are complex, low SES households often have less enriching home environments and parent-child interactions. This study investigated the extent to which environmental/behavioral factors (quality of maternal care and richness of the postnatal environment) may modify adverse effects from Pb exposure. METHODS: Long-Evans female rats were randomly assigned to Control (no Pb), Early Postnatal (EPN: birth through weaning), or Perinatal (PERI: 14 days pre-mating through weaning) Pb exposure groups. From postnatal days (PNDs) 2-9, maternal care behaviors were observed, and dams were classified as low or high maternal care based on amounts of licking/grooming and arched back nursing. At weaning, pups were randomly assigned to enriched or non-enriched environments. At PND 55, animals began trace fear conditioning and associative memory was tested on days 1, 2, and 10 postconditioning. RESULTS: Control offspring showed no significant effects of maternal care or enrichment on task performance. Females with EPN-Pb exposure and males with PERI-Pb exposure living in the non-enriched environment and having an LMC mother had significant memory impairments at days 2 and 10 that were not observed in comparably housed animals with HMC mothers. Enriched animals had no deficits, regardless of maternal care status. CONCLUSION: These results show the potential for modulatory influences of maternal care and housing environment on protecting against or reversing at least one aspect of Pb-induced cognitive/behavioral dysfunction.

Postnatal rearing environment alters pup cues for caregiver-offspring interactions.

Maternal behavior experienced in early life provides essential scaffolding to infant psychobiology with life-long effects on neurobiological and behavioral outcomes. However, infants are not passive recipients of caregiving. Evidence in rodents suggests that pups actively contribute to dam-pup interactions by soliciting maternal care with auditory, tactile, and hormonal cues. The limited bedding and nesting material (LBN) rearing manipulation induces changes in maternal care that have been attributed to maternal stress caused by the low-resource environment. The goal of the current study was to determine whether LBN also alters pup cues for maternal behavior, with implications for the mechanism of LBN-induced effects. Rat dams and pups were randomly assigned to LBN or Control rearing conditions on postnatal day (P) 0-6 and pups were fostered to the same or different condition on P6-13. LBN increased pup-directed maternal behaviors measured through 24 h monitoring using machine learning based automated analysis. LBN altered several pup cues known to affect maternal behavior including reducing pup core body temperature, reducing body weight, and altering pup vocalizations on P6 and P12. P6-13 LBN-exposed pups had elevated serum testosterone, which positively correlated with maternal licking and grooming. LBN reduced pup movement between nest attendance onset and the start of nursing, which was negatively related to dam nursing latency and contributed to longer nursing latency in LBN dams. P0-6 pup exposure to LBN also led to longer nest attendance bouts and shorter licking and grooming bouts on P7 and P9, suggesting lasting effects of LBN on pups. These data demonstrate that LBN changes pup behavioral and hormonal signals consistent with eliciting more maternal care, contributing to augmented pup-directed behaviors. This bidirectional interplay may be a critical mechanism involved in the lasting effects of early life environments.

Mother-infant attachment from the perspective of young mothers: Does the data support a maternal instinct?

Some conceptualizations of attachment imply an instinctual behavior that occurs naturally. Mothers who endorse this view are at greater risk for psychological stress, depression, and harsh parenting styles if they do not feel an immediate bond with their infant postpartum. The purpose of this study is to explore actual experiences of attachment from the perspective of young mothers (N = 75, Mage = 19.45 years) and based on these findings the extent to which there is empirical support for a maternal instinct. Mothers were interviewed at home three times (2 weeks, four months, and seven months postpartum), and interviews were thematically analyzed using an open coding method. Three broad themes and six sub-themes emerged: 1) experiences with the immediacy of attachment at birth are diverse (traumatic birth experience, sense of a maternal identity), 2) contextual factors on the bonding experience (physical touch-based caretaking, parenting stress and depression), and 3) time spent parenting influences attachment (reciprocity, parental confidence/knowledge). In conclusion, we could not find empirical evidence to support an innate maternal instinct. Despite diverse experiences with felt attachment at birth, all mothers perceived that the mother-infant connection was influenced by contextual factors after birth and was strengthened over time with more care-taking experience. This suggests that mothers likely developed a "maternal instinct" through repetitive interaction with their infant as the primary caretaker rather than a genetic predisposition to be superior nurturing parents.

Genetic analysis of a maternal assistance score in sheep.

Maternal behaviour is important for lamb survival, as ewes perform many behaviours that affect the chances of a lamb surviving. Collecting maternal behaviour data directly at lambing is time-consuming and not considered suitable for acquiring the large volumes of data that would be required for using as selection criteria within commercial breeding flocks. The aim of this study was to investigate if a simple scoring system is heritable and assesses the expression of behaviours that reduce the probability of lamb mortality. Ewe behaviour was scored on a 3-point Maternal Assistance Score (MAS): (1) the ewe shows a high level of maternal interest (assumed if no intervention required); (2) the ewe shows limited interest in her lamb; and (3) the ewe shows no interest in her lamb. A total of 19 453 MAS were collected over 12 years, across 24 farms (including both indoor and outdoor lambing systems) and 12 different breed lines that make up the Innovis breeding programme. Ewe parity, breed, number of lambs carried, flock, lambing batch, lambing day within flock and pre-mating weight all had a significant effect on MAS (P < 0.05). The maternal assistance score was shown to be heritable (h2 = 0.05) and repeatable (0.10), positively genetically correlated to lambing difficulty (rg = 0.29) and amount of assistance the lamb required to suckle from the ewe (rg = 0.88), and negatively genetically correlated with the number of lambs successfully reared (rg = 0.49). This study shows that an easy-to-measure score can be used by shepherds with large breeding flocks, based on whether the ewe requires further assistance to support her lamb rearing. The score could be used in breeding programmes to select for lamb rearing ability in the future and potentially lead to an improvement in lamb welfare through a reduction in mortality.

Dynamic coupling of maternal sensitivity and toddlers' responsive/assertive behaviors predicts children's behavior toward peers during the preschool years.

We examined the extent to which dynamic coupling of (a) maternal sensitivity and (b) children's responsive and assertive behaviors toward mothers during a semistructured play session predicts children's responsive and assertive behavior toward an unfamiliar peer at 39 months and a close friend at 58 and 66 months. Maternal and child behaviors were rated in 30-s epochs during play when children were 32 months old (Time 1; N = 128; 66 girls). Children were rated on their responsiveness and assertiveness toward an unfamiliar peer in the early preschool years (Time 2) and toward a friend in the late preschool years (Time 3). Residual dynamic structural equation models showed that stronger positive contemporaneous coupling of maternal sensitivity and children's responsiveness in a given 30-s epoch of the play session predicted greater observed responsiveness toward a friend in the late preschool years, after controlling for mean levels of maternal sensitivity and child responsiveness. On the other hand, positive contemporaneous coupling of maternal sensitivity and child assertiveness predicted children's higher levels of observed assertiveness toward an unfamiliar peer in the early preschool years, after controlling for mean levels of maternal sensitivity and child assertiveness. Results suggest that the dynamic coupling of specific positive behaviors during mother-child interaction may provide children with social scripts to draw on in diverse peer contexts. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Role of sexually dimorphic oxytocin receptor-expressing neurons in the anteroventral periventricular nucleus on maternal behavior.

Oxytocin is a neuropeptide produced by magnocellular neurosecretory neurons located primarily in the supraoptic nucleus and paraventricular nucleus of the hypothalamus. The long axons of these neurons project to the neurohypophysis where oxytocin is released into the general circulation in response to the physiological demands. Oxytocin plays critical roles in female reproductive physiology, specifically in uterine contraction during labor and milk ejection while nursing. Oxytocin is also called "the love hormone" due to its modulatory roles in prosocial behaviors, including social recognition, maternal behavior, and pair bonding. Oxytocin influences behaviors by binding to oxytocin receptors (OXTR) located in various parts of the brain. Previously, we discovered a group of estrogen-dependent OXTR neurons that is exclusively present in the anteroventral periventricular nucleus (AVPV) of females but not of males. The female-specific expression of OXTR in the AVPV is a rare case of neurochemically-demonstrated, all-or-none sexual dimorphism in the brain. In this review, the cellular characterization and functional significance of the sexually dimorphic OXTR neurons in the AVPV as well as the clinical implications of the research will be discussed.

High fat diet consumption and social instability stress impair stress adaptation and maternal care in C57Bl/6 dams.

Poor maternal diet and psychosocial stress represent two environmental factors that can significantly impact maternal health during pregnancy. While various mouse models have been developed to study the relationship between maternal and offspring health and behaviour, few incorporate multiple sources of stress that mirror the complexity of human experiences. Maternal high-fat diet (HF) models in rodents are well-established, whereas use of psychosocial stress interventions in female mice are still emerging. The social instability stress (SIS) paradigm, serves as a chronic and unpredictable form of social stress. To evaluate the combined effects of a poor maternal diet and intermittent social stress on maternal health and behaviour, we developed a novel maternal stress model using adult female C57Bl/6 mice. We observed that all HF+ mice demonstrated rapid weight gain, elevated fasting blood glucose levels and impaired glucose tolerance independent of the presence (+) or absence (-) of SIS. Behavioural testing output revealed anxiety-like behaviours remained similar across all groups prior to pregnancy. However, integrated anxiety z-scores revealed a mixed anxious profile amongst HF+/SIS+ females prior to pregnancy. HF+/SIS+ females also did not show reduced plasma ACTH and corticosterone levels that were observed in our other HF+ and HF- stress groups after SIS exposure. Further, HF+/SIS+ females demonstrated significant postpartum maternal neglect, resulting in fewer numbers of live offspring. These findings suggest that prolonged maternal HF diet consumption, coupled with previous exposure to SIS, places a significant burden on the maternal stress response system, resulting in reduced parental investment and negative postpartum behaviour towards offspring.

Deactivation, hyperactivation, and anomalous content in the attachment script assessment: stability over time and significance for parenting behavior and physiology.

This study examined the stability of Attachment Script Assessment (ASA) deactivation, hyperactivation, and anomalous content and their significance for parenting outcomes in mothers (Mage = 31 years; 78% White/European American) and 6-month-old infants. Comparable to ASA secure base script knowledge (SBSK), mothers' ASA deactivation, hyperactivation, and anomalous content were significantly, moderately stable over two years (r's = .40 - .43). Mothers' ASA hyperactivation and anomalous content were associated with greater maternal intrusiveness, whereas ASA deactivation was associated with greater detachment and less intrusiveness. Only ASA anomalous content was associated with lower maternal sensitivity. Mothers' ASA deactivation was associated with less dynamic change in respiratory sinus arrhythmia during the Still-Face Procedure-reflective of limited mobilization of physiological resources to support responding to infants. Findings support the validity of ASA deactivation, hyperactivation, and anomalous content scripts, and demonstrate their utility in examining adult attachment stability and predictive significance for parent-child outcomes.

Co-regulation, relationship quality, and infant distress vocalizations observed during mother-infant interactions: Influences of maternal depression and different contexts.

Mother-infant interactions are co-regulated and provide the foundation for mother-infant relationship quality. The implications of maternal depression and contextual demands (i.e., reinstating the interaction following maternal unavailability and vocalized infant distress) on observationally coded co-regulation in mother-infant dyads (n = 40) at 4-months was investigated. Associations among co-regulation patterns and mother-infant relationship quality was also examined. Dyads participated in Still-Face (SF) and Separation (SP) procedures, with periods of maternal emotional and physical unavailability. Co-regulation was captured using the Revised Relational Coding System. Relationship quality was examined using the Emotional Availability Scales. Dyads in the depressed group had significantly more unilateral exchanges than the non-depressed group following the SF and SP perturbations. The depressed group also had significantly more distress vocalizations during the SP perturbation than the non-depressed group. Co-regulation in the depressed group was less disrupted by the SF perturbation. Positive relationship quality dimensions (maternal sensitivity, structuring, and infant responsiveness) were associated with more symmetrical and less unilateral co-regulation regardless of the interaction period. There were also context-specific results pertaining to patterns of co-regulation and associated maternal hostility and infant responsiveness. Results highlight co-regulatory differences in depressed mothers and their infants and how these differences are exacerbated by contextual demands.

"My baby is ready to learn"-The role of infant pointing in redirecting maternal responses to be more informative.

Caregivers may perceive pointing as an indication of infants' readiness to learn, thereby increasing their tendency to label objects regardless of the infant's gesture type and context. This was investigated in this study by tracking 35 infants at home at the ages of 11 and 13 months and observing their interactions with their mothers during object manipulation. We focused on four types of communicative gestures: typical giving gestures, gestures contingent on exploration, gestures contingent on play, and pointing. We analyzed maternal response tendencies, including affirmation, naming, discourse, and pretense. The results revealed that when infants reached the age of 13 months, they tripled their pointing production; in turn, the maternal response changed entirely, with naming becoming the preferred response to all types of gestures. Furthermore, when infants were 13 months old and offered an object contingent on play acts, mothers increased their pretense acts sevenfold. Based on the most informative responses to infants among those examined, we argue that an increase in the number of pointing gestures may gradually be associated with the establishment of the maternal perception that an infant is ready to learn and a subsequent increase in naming and pretense production by the mother.

Infants' cortisol reactivity and infant-mother cortisol synchrony in urban Chinese families: The role of maternal control strategy.

Maternal control strategy refers to a mother's practices used to impel, inhibit, guide, or shape their children's behaviors during mother-child interaction. The present study examined control strategies used by Chinese urban mothers and how they associated with infants' cortisol trajectory and infant-mother cortisol synchrony during a separation task. Participants were 115 infant-mother dyads. Maternal control strategy was assessed during mother-infant free-play when the infants were 6 months (T1) and 1 year (T2) old. Salivary cortisol samples were collected from both infants and mothers during a stress-inducing task at T2. The results indicated that mothers most frequently adopted the moderate power control strategy, at both T1 and T2. T1 maternal low control strategy significantly predicted infants' cortisol response curve, namely infants of mothers who predominantly adopted a low power control strategy had a more dynamic reactivity and recovery in their cortisol response to the separation task. Positive cortisol synchrony was observed between mothers and infants during the separation stress condition. In addition, T2 maternal high power control strategy accounted for inter-individual variations in infant-mother cortisol synchrony, such that mothers who predominantly adopted a high power control strategy exhibited a heightened level of cortisol synchrony with their infants. Our findings suggest that targeted training in maternal control strategies could help mothers calibrate their infants' adrenocortical regulation.

Pubertal maternal presence reduces anxiety and increases adult neurogenesis in Kunming mice offspring.

Puberty is a critical period of emotional development and neuroplasticity. However, most studies have focused on early development, with limited research on puberty, particularly the parental presence. In this study, four groups were established, and pubertal maternal presence (PMP) was assessed until postnatal days 21 (PD21), 28 (PD28), 35 (PD35), and 42 (PD42), respectively. The social interaction and anxiety behaviors, as well as the expression of oxytocin (OT) in the paraventricular nucleus (PVN) and supraoptic nucleus (SON), and the number of new generated neurons and the expression of estrogen receptor alpha (ERα) in the dentate gyrus (DG) were assessed. The results suggest that there is a lot of physical contact between the mother and offspring from 21 to 42 days of age, which reduces anxiety in both female and male offspring in adulthood; for example, the PMP increased the amount of time mice spent in the center area in the open field experiment and in the bright area in the light-dark box experiment. PMP increased OT expression in the PVN and SON and the number of newly generated neurons in the DG. However, there was a sexual difference in ERα, with ERα increasing in females but decreasing in males. In conclusion, PMP reduces the anxiety of offspring in adulthood, increases OT in the PVN and SON, and adult neurogenesis; ERα in the DG may be involved in this process.

Limited Bedding and Nesting as a Model for Early-Life Adversity in Mice.

Early-life adversity (ELA), such as abuse, neglect, lack of resources, and an unpredictable home environment, is a known risk factor for developing neuropsychiatric disorders such as depression. Animal models for ELA have been used to study the impact of chronic stress on brain development, and typically rely on manipulating the quality and/or quantity of maternal care, as this is the major source of early-life experiences in mammals, including humans. Here, a detailed protocol for employing the Limited Bedding and Nesting (LBN) model in mice is provided. This model mimics a low-resource environment, which provokes fragmented and unpredictable patterns of maternal care during a critical developmental window (postnatal days 2-9) by limiting the amount of nesting materials given to the dam to build a nest for her pups and separating the mice from the bedding via a mesh platform in the cage. Representative data are provided to illustrate the changes in maternal behavior, as well as the diminished pup weights and long-term changes in basal corticosterone levels, that result from the LBN model. As adults, offspring reared in the LBN environment have been shown to exhibit an aberrant stress response, cognitive deficits, and anhedonia-like behavior. Therefore, this model is an important tool to define how the maturation of stress-sensitive brain circuits is altered by ELA and results in long-term behavioral changes that confer vulnerability to mental disorders.

Neurons for infant social behaviors in the mouse zona incerta.

Understanding the neural basis of infant social behaviors is crucial for elucidating the mechanisms of early social and emotional development. In this work, we report a specific population of somatostatin-expressing neurons in the zona incerta (ZISST) of preweaning mice that responds dynamically to social interactions, particularly those with their mother. Bidirectional neural activity manipulations in pups revealed that widespread connectivity of preweaning ZISST neurons to sensory, emotional, and cognitive brain centers mediates two key adaptive functions associated with maternal presence: the reduction of behavior distress and the facilitation of learning. These findings reveal a population of neurons in the infant mouse brain that coordinate the positive effects of the relationship with the mother on an infant's behavior and physiology.

The effects of buprenorphine and morphine during pregnancy: Impact of exposure length on maternal brain, behavior, and offspring neurodevelopment.

The escalating incidence of opioid-related issues among pregnant women in the United States underscores the critical necessity to understand the effects of opioid use and Medication for Opioid Use Disorders (MOUDs) during pregnancy. This research employed a translational rodent model to examine the impact of gestational exposure to buprenorphine (BUP) or morphine on maternal behaviors and offspring well-being. Female rats received BUP or morphine before conception, representing established use, with exposure continuing until postnatal day 2 or discontinued on gestational day 19 to mimic treatment cessation before birth. Maternal behaviors - including care, pup retrieval, and preference - as well as hunting behaviors and brain neurotransmitter levels were assessed. Offspring were evaluated for mortality, weight, length, milk bands, surface righting latency, withdrawal symptoms, and brain neurotransmitter levels. Our results reveal that regardless of exposure length (i.e., continued or discontinued), BUP resulted in reduced maternal care in contrast to morphine-exposed and control dams. Opioid exposure altered brain monoamine levels in the dams and offspring, and was associated with increased neonatal mortality, reduced offspring weight, and elevated withdrawal symptoms compared to controls. These findings underscore BUP's potential disruption of maternal care, contributing to increased pup mortality and altered neurodevelopmental outcomes in the offspring. This study calls for more comprehensive research into prenatal BUP exposure effects on the maternal brain and infant development with the aim to mitigate adverse outcomes in humans exposed to opioids during pregnancy.

Facing infant cuteness: How nurturing care motivation and oxytocin system gene methylation are associated with responses to baby schema features.

Baby schema features are a specific set of physical features-including chubby cheeks, large, low-set eyes, and a large, round head-that have evolutionary adaptive value in their ability to trigger nurturant care. In this study among nulliparous women (N = 81; M age = 23.60, SD = 0.44), we examined how sensitivity to these baby schema features differs based on individual variations in nurturant care motivation and oxytocin system gene methylation. We integrated subjective ratings with measures of facial expressions and electroencephalography (EEG) in response to infant faces that were manipulated to contain more or less pronounced baby schema features. Linear mixed effects analyses demonstrated that infants with more pronounced baby schema features were rated as cuter and participants indicated greater motivation to take care of them. Furthermore, infants with more pronounced baby schema features elicited stronger smiling responses and enhanced P2 and LPP amplitudes compared to infants with less pronounced baby schema features. Importantly, individual differences significantly predicted baby schema effects. Specifically, women with low OXTR methylation and high nurturance motivation showed enhanced differentiation in automatic neurophysiological responses to infants with high and low levels of baby schema features. These findings highlight the importance of considering individual differences in continued research to further understand the complexities of sensitivity to child cues, including facial features, which will improve our understanding of the intricate neurobiological system that forms the basis of caregiving behavior.

Perinatal protein malnutrition alters maternal behavior and leads to maladaptive stress response, neurodevelopmental delay and disruption on DNA methylation machinery in female mice offspring.

Deficiencies in maternal nutrition have long-term consequences affecting brain development of the progeny and its behavior. In the present work, female mice were exposed to a normal-protein or a low-protein diet during gestation and lactation. We analyzed behavioral and molecular consequences of malnutrition in dams and how it affects female offspring at weaning. We have observed that a low-protein diet during pregnancy and lactation leads to anxiety-like behavior and anhedonia in dams. Protein malnutrition during the perinatal period delays physical and neurological development of female pups. Glucocorticoid levels increased in the plasma of malnourished female offspring but not in dams when compared to the control group. Interestingly, the expression of glucocorticoid receptor (GR) was reduced in hippocampus and amygdala on both malnourished dams and female pups. In addition, malnourished pups exhibited a significant increase in the expression of Dnmt3b, Gadd45b, and Fkbp5 and a reduction in Bdnf VI variant mRNA in hippocampus. In contrast, a reduction on Dnmt3b has been observed on the amygdala of weaned mice. No changes have been observed on global methylation levels (5-methylcytosine) in hippocampal genomic DNA neither in dams nor female offspring. In conclusion, deregulated behaviors observed in malnourished dams might be mediated by a low expression of GR in brain regions associated with emotive behaviors. Additionally, low-protein diet differentially deregulates the expression of genes involved in DNA methylation/demethylation machinery in female offspring but not in dams, providing an insight into regional- and age-specific mechanisms due to protein malnutrition.

Prolactin modulates changes in parental care behaviour in response to perceived paternity in bluegill sunfish (Lepomis macrochirus).

Prolactin is a hormone conserved across all vertebrates and is renowned for its role in reproduction and parental care. Previous studies on prolactin in fish have primarily relied on administration of mammalian prolactin and have suggested that increases in prolactin lead to greater parental care. However, the influence of endogenous prolactin on fish parental care remains unknown. Here, we measure circulating concentrations of endogenous prolactin during parental care in a fish and link these concentrations to parental care behaviour. We provide evidence that male bluegill sunfish with higher circulating concentrations of prolactin provide more parental care to their offspring. Furthermore, we show that nesting males with experimentally reduced perceived paternity have lower circulating prolactin concentrations and perform fewer parental behaviours, facilitating an adaptive investment in offspring in response to paternity cues. Our findings not only confirm the role of endogenous prolactin in modulating parental care behaviour in a fish but also provide a mechanism underlying the adaptive changes in parental care made in response to perceived paternity.