Copulatory behaviors and body condition predict post-mating female hormone concentrations, fertilization success, and primary sex ratios in Japanese quail

The effect of infection risk on female blood transcriptomics

Defenses against pathogens can take on many forms. For instance, behavioral avoidance of diseased conspecifics is widely documented. Interactions with these infectious conspecifics can also, however, lead to physiological changes in uninfected animals, an effect that is much less well understood. These changes in behavior and physiology are particularly important to study in a reproductive context, where they can impact reproductive decisions and offspring quality. Here, we studied how an acute (3 h) exposure to an immune-challenged male affected female blood transcriptomics and behavior. We predicted that females paired with immune-challenged males would reduce eating and drinking behaviors (as avoidance behaviors) and that their blood would show activation of immune and stress responses. We used female Japanese quail as a study system because they have been shown to respond to male traits, in terms of their own physiology and egg investment. Only two genes showed significant differential expression due to treatment, including an increase in the threonine dehydrogenase (TDH) transcript, an enzyme important for threonine breakdown. However, hundreds of genes in pathways related to activation of immune responses showed coordinated up-regulation in females exposed to immune-challenged males. Suppressed pathways revealed potential changes to metabolism and reduced responsiveness to glucocorticoids. Contrary to our prediction, we found that females paired with immune-challenged males increased food consumption. Water consumption was not changed by treatment. These findings suggest that even short exposure to diseased conspecifics can trigger both behavioral and physiological responses in healthy animals.

Maternal Responses in the Face of Infection Risk

When animals are sick, their physiology and behavior change in ways that can impact their offspring. Research is emerging showing that infection risk alone can also modify the physiology and behavior of healthy animals. If physiological responses to environments with high infection risk take place during reproduction, it is possible that they lead to maternal effects. Understanding whether and how high infection risk triggers maternal effects is important to elucidate how the impacts of infectious agents extend beyond infected individuals and how, in this way, they are even stronger evolutionary forces than already considered. Here, to evaluate the effects of infection risk on maternal responses, we exposed healthy female Japanese quail to either an immune-challenged (lipopolysaccharide [LPS] treated) mate or to a healthy (control) mate. We first assessed how females responded behaviorally to these treatments. Exposure to an immune-challenged or control male was immediately followed by exposure to a healthy male, to determine whether treatment affected paternity allocation. We predicted that females paired with immune-challenged males would avoid and show aggression towards those males, and that paternity would be skewed towards the healthy male. After mating, we collected eggs over a 5-day period. As an additional control, we collected eggs from immune-challenged females mated to healthy males. We tested eggs for fertilization status, embryo sex ratio, as well as albumen corticosterone, lysozyme activity, and ovotransferrin, and yolk antioxidant capacity. We predicted that immune-challenged females would show the strongest changes in the egg and embryo metrics, and that females exposed to immune-challenged males would show intermediate responses. Contrary to our predictions, we found no avoidance of immune-challenged males and no differences in terms of paternity allocation. Immune-challenged females laid fewer eggs, with an almost bimodal distribution of sex ratio for embryos. In this group, albumen ovotransferrin was the lowest, and yolk antioxidant capacity decreased over time, while it increased in the other treatments. No differences in albumen lysozyme were found. Both females that were immune-challenged and those exposed to immune-challenged males deposited progressively more corticosterone in their eggs over time, a pattern opposed to that shown by females exposed to control males. Our results suggest that egg-laying Japanese quail may be able to respond to infection risk, but that additional or prolonged sickness symptoms may be needed for more extensive maternal responses.

The insemination status and social context influences quail laying and social behavior: A novel experimental set up

Japanese quails in wild life live in small groups with females being even solitary during the laying period. Although it is a poultry species widely used for egg production, information regarding laying behavior motivations or influencing variables is scarce. Our study focuses on evaluating along 7 d the quail laying behavior in a novel environmental set up. This set up allows the female to choose between remaining separated from a conspecific in one side of the apparatus or to voluntarily enter their space (box-mate side) and interact with it. We evaluated whether the female insemination status prior to enter the environmental set up, and the presence of a female or a male partner in the box-mate side can influence their laying and social behavior. Thus, 4 experimental groups were established. Females spent a higher (P < 0.05) percentage of time in the box-mate side than in their separated sector in all groups. In 3 of the 4 experimental groups (non-inseminated females interacting with a female or a male box-mate, and inseminated females interacting with a male box-mate) females also laid a greater percentage (≥65%, P < 0.05, in all cases) of eggs in the box-mate sector than in their separated sector. However, the group of inseminated females that interacted with a female box-mate shifted their egg distribution and laid equally between both sides of the apparatus. Aggressive social interactions were reduced (P < 0.05) throughout the testing days but this was depending upon the female insemination status and the sex of their box-mate. Findings suggest that females can change their laying side choice when they are inseminated but depending on the sex identity of their box-mate partners. Thus, providing quail female breeders with the option of laying their eggs in separated enclosures from conspecifics could be key to favor their well-being.

Effects of the maternal and current social environment on female body mass and reproductive traits in Japanese quail (Coturnix japonica)

The social environment of breeding females can affect their phenotype, with potential adaptive maternal effects on offspring that experience a similar environment. We housed Japanese quail (Coturnix japonica) females in two group sizes (pairs versus groups of four) and studied the effects on their offspring under matched and mismatched conditions. We measured F1 body mass, reproduction, and plasma levels of androgens and corticosterone. F1 group housing led to an increase in body mass. In addition, F1 group housing had a positive effect on mass in daughters of pair-housed P0 females only, which were heaviest under mismatched conditions. At the time of egg collection for the F2 generation, F1 group-housed females were heavier, irrespective of the P0 treatment. F1 females in groups laid heavier eggs, with higher hatching success, and produced heavier offspring, most likely a maternal effect of F1 mass. F1 plasma hormones were affected by neither the P0 nor the F1 social environment. These results contrasted with effects in the P0 generation (reported previously), in which plasma hormone levels, but not mass, differed between social environments. This may be due to changes in adult sex ratios as P0 females were housed with males, whereas F1 females encountered males only during mating. Our study demonstrates potentially relevant mismatch effects of the social environment on F1 body mass and maternal effects on F2 offspring, but further study is needed to understand their adaptive significance and physiological mechanisms.

Physiological increase of yolk testosterone level does not affect oxidative status and telomere length in gull hatchlings

Conditions experienced during early-life can cause the onset of oxidative stress, resulting in pervasive effects on diverse life-history traits, including lifespan. In birds, maternally-transferred egg substances may exert positive or negative influence over the offspring phenotype. Among these, testosterone can upregulate the bioavailability of certain antioxidants but simultaneously promotes the production of pro-oxidants, leading to an oxidative stress situation, which is one of the main forces causing telomere attrition However, no study has investigated the role of this androgen on telomere dynamics in birds and little is known about the effects of yolk testosterone on oxidative status in early-life of these species. We physiologically increased the levels of yolk testosterone by in ovo injections in yellow-legged gull (Larus michahellis) to evaluate the effects induced by this androgen on hatchlings plasma total antioxidant capacity, amount of pro-oxidant molecules and telomere length at hatching. Testosterone supplementation did not increase hatchling body growth, did not result in the overproduction of pro-oxidant molecules nor a reduction of antioxidant capacity. Accordingly, telomere length at hatching was not affected by testosterone treatment, although hatchlings from the third-laid eggs showed shorter telomeres than their siblings from first- and second-laid eggs, independently of testosterone treatment. Our results suggest that injection of physiological levels of testosterone does not induce oxidative stress to hatchlings and, consequently do not affect telomere dynamics during early post-natal periods.

No evidence for sex-specific effects of the maternal social environment on offspring development in Japanese quail (Coturnix japonica)

The social environment of reproducing females can cause physiological changes, with consequences for reproductive investment and offspring development. These prenatal maternal effects are often found to be sex-specific and may have evolved as adaptations, maximizing fitness of male and female offspring for their future environment. Female hormone levels during reproduction are considered a potential mechanism regulating sex allocation in vertebrates: high maternal androgens have repeatedly been linked to increased investment in sons, whereas high glucocorticoid levels are usually related to increased investment in daughters. However, results are not consistent across studies and therefore still inconclusive. In Japanese quail (Coturnix japonica), we previously found that pair-housed females had higher plasma androgen levels and tended to have higher plasma corticosterone levels than group-housed females. In the current study we investigate whether these differences in maternal social environment and physiology affect offspring sex allocation and physiology. Counter to our expectations, we find no effects of the maternal social environment on offspring sex ratio, sex-specific mortality, growth, circulating androgen or corticosterone levels. Also, maternal corticosterone or androgen levels do not correlate with offspring sex ratio or mortality. The social environment during reproduction therefore does not necessarily modify sex allocation and offspring physiology, even if it causes differences in maternal physiology. We propose that maternal effects of the social environment strongly depend upon the type of social stimuli and the timing of changes in the social environment and hormones with respect to the reproductive cycle and meiosis.

The genetics of egg retention and fertilization success in Drosophila: One step closer to understanding the transition from facultative to obligate viviparity

Oviparous, facultative egg retention enables Drosophila females to withhold fertilized eggs in their reproductive tracts until circumstances favor oviposition. The propensity to retain fertilized eggs varies greatly between species, and is correlated with other reproductive traits, such as egg size and ovariole number. While previous studies have described the phenomenon, no study to date has characterized within-species variation or the genetic basis of the trait. Here, we develop a novel microscope-based method for measuring egg retention in Drosophila females and determine the range of phenotypic variation in mated female egg retention in a subset of 91 Drosophila Genetic Reference Panel (DGRP) lines. We inferred the genetic basis of egg retention using a genome-wide association study (GWAS). Further, the scoring of more than 95,000 stained, staged eggs enabled estimates of fertilization success for each line. We found evidence that ovary- and spermathecae-related genes as well as genes affecting olfactory behavior, male mating behavior, male-female attraction and sperm motility may play a crucial role in post-mating physiology. Based on our findings we also propose potential evolutionary routes toward obligate viviparity. In particular, we propose that the loss of fecundity incurred by viviparity could be offset by benefits arising from enhanced mate discrimination, resource specialization, or modified egg morphology.

Social environment during egg laying: Changes in plasma hormones with no consequences for yolk hormones or fecundity in female Japanese quail, Coturnix japonica

The social environment can have profound effects on an individual's physiology and behaviour and on the transfer of resources to the next generation, with potential consequences for fecundity and reproduction. However, few studies investigate all of these aspects at once. The present study housed female Japanese quail (Coturnix japonica) in pairs or groups to examine the effects on hormone concentrations in plasma and yolk and on reproductive performance. Circulating levels of androgens (testosterone and 5-α-dihydrotestosterone) and corticosterone were measured in baseline samples and after standardised challenges to assess the responsiveness of the females' endocrine axes. Effects of the social environment on female fecundity were analysed by measuring egg production, egg mass, fertilization rates, and number of hatched offspring. Counter to expectation, females housed in pairs had higher plasma androgen concentrations and slightly higher corticosterone concentrations than females housed in groups, although the latter was not statistically significant. Pair vs. group housing did not affect the females' hormonal response to standardised challenges or yolk testosterone levels. In contrast to previous studies, the females' androgen response to a gonadotropin-releasing hormone challenge was not related to yolk testosterone levels. Non-significant trends emerged for pair-housed females to have higher egg-laying rates and higher fertility, but no differences arose in egg weight or in the number, weight or size of hatchlings. We propose that our unexpected findings are due to differences in the adult sex ratio in our social treatments. In pairs, the male may stimulate female circulating hormone levels more strongly than in groups where effects are diluted due to the presence of several females. Future studies should vary both group size and sex composition to disentangle the significance of sexual, competitive and affiliative social interactions for circulating and yolk hormone levels, and their consequences for subsequent generations.

Identification with Stimuli Moderates Women's Affective and Testosterone Responses to Self-Chosen Erotica

Sexual thoughts are sufficient to increase testosterone (T) in women, yet erotic films are not. A key confound in past studies is autonomy in stimulus selection: women choose the content of their sexual thoughts but films have been selected by researchers. We hypothesized that self-chosen erotic films, compared to researcher-chosen erotic films, would (1) increase women's self-reported arousal, enjoyment, and identification with stimuli, and decrease negative affect; and (2) increase T. Participants (N = 116 women) were randomly assigned to a neutral documentary condition or one of three erotic film conditions: high choice (self-chosen erotica from participants' own sources), moderate choice (self-chosen erotica from films preselected by sexuality researchers), or no choice (researcher-chosen erotica). Participants provided saliva samples for T before and after viewing the film in the privacy of their homes. Compared to researcher-chosen erotica, self-chosen erotica increased self-reported arousal and enjoyment, but also unexpectedly disgust, guilt, and embarrassment. Self-chosen erotica only marginally increased identification with stimuli compared to researcher-chosen erotica. Overall, film condition did not affect T, but individual differences in identification moderated T responses: among women reporting lower levels of identification, the moderate choice condition decreased T compared to the no choice condition, but this difference was not observed among women with higher identification. These results highlight the importance of cognitive/emotional factors like identification for sexually modulated T. However, self-chosen erotica results in more ambivalent rather than unequivocally positive cognitive/emotional responses, perhaps because stigma associated with viewing erotica for women becomes more salient when choosing stimuli.

Effects of gendered behavior on testosterone in women and men

Testosterone is typically understood to contribute to maleness and masculinity, although it also responds to behaviors such as competition. Competition is crucial to evolution and may increase testosterone but also is selectively discouraged for women and encouraged for men via gender norms. We conducted an experiment to test how gender norms might modulate testosterone as mediated by two possible gender→testosterone pathways. Using a novel experimental design, participants (trained actors) performed a specific type of competition (wielding power) in stereotypically masculine vs. feminine ways. We hypothesized in H1 (stereotyped behavior) that wielding power increases testosterone regardless of how it is performed, vs. H2 (stereotyped performance), that wielding power performed in masculine but not feminine ways increases testosterone. We found that wielding power increased testosterone in women compared with a control, regardless of whether it was performed in gender-stereotyped masculine or feminine ways. Results supported H1 over H2: stereotyped behavior but not performance modulated testosterone. These results also supported theory that competition modulates testosterone over masculinity. Our findings thus support a gender→testosterone pathway mediated by competitive behavior. Accordingly, cultural pushes for men to wield power and women to avoid doing so may partially explain, in addition to heritable factors, why testosterone levels tend to be higher in men than in women: A lifetime of gender socialization could contribute to "sex differences" in testosterone. Our experiment opens up new questions of gender→testosterone pathways, highlighting the potential of examining nature/nurture interactions and effects of socialization on human biology.

Mating activity and sperm penetration assay in prediction of the reproduction potential of domestic goose ganders in a harem system

In a natural mating system, the sexual behavior of birds has an important role in fertility success. Non-competitive mating system provides special conditions to study gander-goose interactions. Behavioral and physiological data from a domestic geese breeding flock was used to determine interrelationships between mating activity (MA) parameters, sperm penetration assay (SPA), plasma testosterone (T) concentration, and fertility (F). Moreover, variation in the frequency of gander-goose interactions during the intensive breeding period and the diurnal rhythm (short day - 10L:14D) were evaluated. The 2-/3-year-old ganders (n=15) and 1-/3-year-old geese (1♂:4♀) were observed. On the basis of successful copulation (SCop), groups of ganders with low (33.3%), intermediate (40%), and high (26.7%) frequency were categorized. Frequency of SCop was greater in the morning than in the afternoon. For the entire breeding period, SPA results obtained for the low frequency group were less than for the intermediate group. Fertility success for ganders from both low and intermediate groups was similar. There was a lack of association between MA, plasma T concentration, and SPA results. However, SCop was positively correlated with fertility. It is recommended that SCop be considered as a prognostic parameter for monitoring of ganders' reproductive potential. It is recommended that the sexual behavior of ganders be evaluated before the 1200h of the day. The SCop with an average frequency of 0.4-0.8 times during the day light hours appears to be associated with fertility results that are satisfactory for geese husbandry. Additionally, the SPA may be considered for identification of ganders with poor reproductive potential to facilitate the decision of changes in harem social structure during the first half of the breeding season.

An individually fitted physical barrier device as a tool to restrict the birds' spatial access: can their use alter behavioral responses?

Social interactions have been extensively studied in poultry in a variety of environmental situations. Many studies allow full social contacts between birds, but there are others in which the interactions are tested through barriers (wire mesh or glass). Thus a situation where, according to their needs, some birds can get access to physical contact with conspecifics while others cannot, would be useful to expand the testing options for social interaction studies. We developed an individual physical barrier device (IPB) that is fitted on the birds to delimit their ambulation areas by preventing them from passing across metal mesh boundaries that IPB free counterparts can easily overcome. The prototypes showing greater efficacy consisted of a small metal bar placed in the bird's back perpendicular to the sagittal plane that slightly exceeds body width, held with a harness fitted by 2 elastic fabric bands around the wings' base. To be useful, the IPB should allow natural movements and not affect the expression of behaviors (non-invasive). This study assessed whether the IPB may alter adult Japanese quail behavioral responses using 4 classical test situations: Open-Field, Runway, Time Budget in Home Box, and Mating Interactions. Open-field ambulatory behaviors were affected 1 h, but not 7 d, after IPB was fitted, suggesting that 7 d (or less) are required to habituate to the device. After that time period, IPB fitted birds showed no differences in any of the behaviors registered in the other 3 tests situations when compared to non IPB fitted birds. Findings suggest that after habituation, the IPB does not affect main behaviors in adult quail. Its application could be expanded if an IPB device is also found suitable for other poultry species.

Effects of acute corticosterone treatment on partner preferences in male and female zebra finches (Taeniopygia guttata)

Stress alters physiology and behavior across species. Most research on the effects of stress on behavior uses chronic stressors, and most are correlational. The effects of acute stressors on physiology and behavior have been mixed. Here, we use zebra finches, a highly gregarious species that forms long-term pair bonds, to test the effects of an acute corticosterone (CORT) on opposite-sex partner preferences over a same-sex individual or a group (the latter is a highly appealing option). We had two competing hypotheses. First, we predicted that acute CORT would alter preferences for the opposite sex bird in both conditions in both sexes. However, since there is a sex difference in the effects of CORT on partner preferences in voles, these effects may be more pronounced in males than in females. To test our hypotheses, we administered 2 doses of CORT (10μg and 20μg) or vehicle (control) using a repeated measures design. In the male vs. female test, there was a significant Sex by Treatment interaction, such that in males, 10μg CORT increased preferences for a female over the male compared to when these same males were treated with saline at baseline. There were no effects of treatment in females. In the opposite-sex vs. group condition, there was an overall effect of Treatment, such that the 10μg dose increased preference for the opposite-sex individual over both saline treatments, regardless of sex. These findings further our understanding of the effects of an acute stressor on sexual partner preferences.

Individual variation in testosterone and parental care in a female songbird; the dark-eyed junco (Junco hyemalis)

When competition for sex-specific resources overlaps in time with offspring production and care, trade-offs can occur. Steroid hormones, particularly testosterone (T), play a crucial role in mediating such trade-offs in males, often increasing competitive behaviors while decreasing paternal behavior. Recent research has shown that females also face such trade-offs; however, we know little about the role of T in mediating female phenotypes in general, and the role of T in mediating trade-offs in females in particular. Here we examine the relationship between individual variation in maternal effort and endogenous T in the dark-eyed junco, a common songbird. Specifically, we measure circulating T before and after a physiological challenge (injection of gonadotropin releasing hormone, GnRH), and determine whether either measure is related to provisioning, brooding, or the amount of T sequestered in egg yolk. We found that females producing more T in response to a challenge spent less time brooding nestlings, but provisioned nestlings more frequently, and deposited more T in their eggs. These findings suggest that, while T is likely important in mediating maternal phenotypes and female life history tradeoffs, the direction of the relationships between T and phenotype may differ from what is generally observed in males, and that high levels of endogenous T are not necessarily as costly as previous work might suggest.

Maternal effects in quail and zebra finches: Behavior and hormones

Maternal effects are influences of parents on offspring phenotype occurring through pathways other than inherited DNA. In birds, two important routes for such transmission are parental behavior and non-DNA egg constituents such as yolk hormones. Offspring traits subject to parental effects include behavior and endocrine function. Research from the Adkins-Regan lab has used three avian species to investigate maternal effects related to hormones and behavior. Experiments with chickens and Japanese quail have shown that maternal sex steroids can influence sex determination to produce biased offspring sex ratios. Because all birds have a ZZ/ZW chromosomal sex determining system in which the female parent determines the sex of the offspring, these results raise the possibility that maternal steroids can influence the outcome of sex chromosome meiosis. Learning has been shown to influence egg investment by female quail in ways that are likely to alter offspring phenotype. In quail, embryonic and exogenous sex steroids have well established and long-lasting effects on sexual differentiation of behavior during a critical period in ovo, but elevated yolk testosterone has long-term effects on behavior that do not seem to be occurring through an alteration in sexual differentiation. In biparental zebra finches, removal of mothers alters not only later behavior, but also the adult response of the hypothalamic-pituitary-adrenal (HPA) axis to an environmental stressor, as indicated by plasma corticosterone. Birds raised only by fathers have lower levels of mRNA for both glucocorticoid receptors in several brain regions as adults. These studies add to the evidence that one generation influences the behavioral or endocrine phenotype of the next through routes other than transmission of DNA. Additional research will be required to understand the adaptive significance of these effects.

The role of steroid hormones in the adjustment of primary sex ratio in birds: compiling the pieces of the puzzle

There is ample evidence that birds have the ability to adjust their offsprings' sex ratios before fertilization occurs. Recent work has focused on pinpointing when during the process of oocyte maturation adjustment of sex ratio takes place. Additionally, there is growing support for the idea that there is hormonal control over the process of adjustment of sex ratio in birds. Whether steroid hormones represent direct mediators of the process, however, remains unclear. This review outlines the precise points during maturation of ovarian follicles during which adjustment of primary sex ratios could potentially occur, compiles the evidence for hormonal involvement in the process of primary adjustment of sex ratio, and discusses potential hormonal targets during maturation and fertilization of oocytes where hormones may trigger adjustment of sex ratio in birds.

Brain aromatase and circulating corticosterone are rapidly regulated by combined acute stress and sexual interaction in a sex-specific manner

Neural production of 17β-oestradiol via aromatisation of testosterone may play a critical role in rapid, nongenomic regulation of physiological and behavioural processes. In brain nuclei implicated in the control of sexual behaviour, sexual or stressfull stimuli induce, respectively, a rapid inhibition or increase in preoptic aromatase activity (AA). In the present study, we tested quail that were either nonstressed or acutely stressed (15 min of restraint) immediately before sexual interaction (5 min) with stressed or nonstressed partners. We measured nuclei-specific AA changes, corresponding behavioural output, fertilisation rates and corticosterone (CORT) concentrations. In males, sexual interaction rapidly reversed stress-induced increases of AA in the medial preoptic nucleus (POM). This time scale (< 5 min) highlights the dynamic potential of the aromatase system to integrate input from stimuli that drive AA in opposing directions. Moreover, acute stress had minimal effects on male behaviour, suggesting that the input from the sexual stimuli on POM AA may actively preserve sexual behaviour despite stress exposure. We also found distinct sex differences in contextual physiological responses: males did not show any effect of partner status, whereas females responded to both their stress exposure and the male partner's stress exposure at the level of circulating CORT and AA. In addition, fertilisation rates and female CORT correlated with the male partner's exhibition of sexually aggressive behaviour, suggesting that female perception of the male can affect their physiology as much as direct stress. Overall, male reproduction appears relatively simple: sexual stimuli, irrespective of stress, drives major neural changes including rapid reversal of stress-induced changes of AA. By contrast, female reproduction appears more nuanced and context specific, with subjects responding physiologically and behaviourally to stress, the male partner's stress exposure, and female-directed male behaviour.

Learning enhances female control over reproductive investment in the Japanese quail

The adaptive significance of learning is supported by studies showing its positive effects on mating behaviour, but they rarely go beyond fertilization success. Here we studied how learning contributes to qualitative reproductive investment, by testing the hypothesis that mating in the context that predicts male appearance has positive effects on female reproductive investment compared with unsignalled mating. Using Japanese quail (Coturnix japonica), we found that effects of mating in the context predicting mating opportunity depend on female body condition and receptivity, while the outcome of unexpected mating depends on male behaviour. In particular, among females mated with the familiar male in the context predicting that he will appear, female condition positively affected the number of fertilized eggs and egg mass and more receptive females tended to produce more sons. Additionally, conditioned females laid heavier eggs for daughters than for sons. In contrast, in females that were mated unexpectedly and with a novel male, the number of fertilized eggs was highly dependent on male behaviour and was negatively related to maternal body condition. Egg mass was not related to body condition, and there were no indications of sex allocation. This is, to our knowledge, the first study demonstrating how female body condition and behaviour interact with the context of mating in shaping maternal reproductive investment.