The question of why maternal stress influences offspring phenotype is of significant interest to evolutionary physiologists. Al- though embryonic exposure to maternally derived glucocorticoids (i.e., corticosterone) generally reduces offspring quality, effects may adaptively match maternal quality with offspring demand. We present results from an interannual field experiment in European starlings (Sturnus vulgaris) designed explicitly to examine the fitness conse- quences of exposing offspring to maternally derived stress hormones. We combined a manipulation of yolk corticosterone (yolk injections) with a manipulation of maternal chick-rearing ability (feather clip- ping of mothers) to quantify the adaptive value of corticosterone- induced offspring phenotypes in relation to maternal quality. We then examined how corticosterone-induced "matching" within this current reproductive attempt affected future fecundity and maternal survival. First, our results provide support that low-quality mothers transferring elevated corticosterone to eggs invest in daughters as predicted by sex allocation theory. Second, corticosterone-mediated sex-biased investment resulted in rapid male-biased mortality re- sulting in brood reduction, which provided a better match between maternal quality and brood demand. Third, corticosterone-mediated matching reduced investment in current reproduction for low-quality mothers, resulting in fitness gains through increased survival and future fecundity. Results indicate that the transfer of stress hormones to eggs by low-quality mothers can be adaptive since corticosterone- mediated sex-biased investment matches the quality of a mother to offspring demand, ultimately increasing maternal fitness. Our results also indicate that the branding of the proximate effects of maternal glucocorticoids on offspring as negative ignores the possibility that short-term phenotypic changes may actually increase maternal fitness.

/pdf/the-adaptive-value-of-stress-induced-phenotypes-effects-of-5bubvrhs1q.pdf

The Adaptive Value of Stress‐Induced Phenotypes: Effects of Maternally Derived Corticosterone on Sex‐Biased Investment, Cost of Reproduction, and Maternal Fitness

https://pure.rug.nl/ws/files/6764847/2011NeurosciBiobehavRevHenriksen.pdf

Prenatal stress in birds: pathways, effects, function and perspectives.

https://www.staff.ncl.ac.uk/melissa.bateson/Salmeto_etal_2011.pdf

Cognitive bias in the chick anxiety-depression model.

Exposure to maternally derived glucocorticoids during embryonic development impacts offspring phenotype. Although many of these effects appear to be transiently 'negative', embryonic exposure to maternally derived stress hormones is hypothesized to induce preparative responses that increase survival prospects for offspring in low-quality environments; however, little is known about how maternal stress influences longer-term survival-related performance traits in free-living individuals. Using an experimental elevation of yolk corticosterone (embryonic signal of low maternal quality), we examined potential impacts of embryonic exposure to maternally derived stress on flight performance, wing loading, muscle morphology and muscle physiology in juvenile European starlings (Sturnus vulgaris). Here we report that fledglings exposed to experimentally increased corticosterone in ovo performed better during flight performance trials than control fledglings. Consistent with differences in performance, individuals exposed to elevated embryonic corticosterone fledged with lower wing loading and had heavier and more functionally mature flight muscles compared with control fledglings. Our results indicate that the positive effects on a survival-related trait in response to embryonic exposure to maternally derived stress hormones may balance some of the associated negative developmental costs that have recently been reported. Moreover, if embryonic experience is a good predictor of the quality or risk of future environments, a preparative phenotype associated with exposure to apparently negative stimuli during development may be adaptive.

/pdf/juveniles-exposed-to-embryonic-corticosterone-have-enhanced-1oc76gwez1.pdf

Juveniles exposed to embryonic corticosterone have enhanced flight performance

In a farm of grandparent broiler breeder chickens, we followed the development of 350 roosters from 6 to 55 weeks of age. Data collected and evaluated from these males included body weight, testicular weight, histologic and immunohistochemistry studies of the testes, hormone levels (testosterone, estradiol and corticosterone) and sperm production. The objective was to understand the factors that affect or influence hatch loss that is commonly observed after 45 weeks of age in breeder flocksare often correlated to broiler breeder male chickens. The results of this study showed that in conjunction with the weight of the rooster, the testicle weight increases quickly after the rooster receives light stimulation. At an older age, the study showed that there is a process of testicular shrinkage, and the same effect is seen in sperm production and testosterone levels in broiler breeder roosters. From the histology evaluation, we defined 5 histologic phases that illustrate the evolution of the testicular tissue: perinatal, infantile, puberty, adult and senile. We observed that the adult males with a body weight <3800 g were infertile or had subfertile levels and also had low levels of testosterone and high levels of corticosterone. In contrast, the heaviest males showed correct testicular vitality, high levels of testosterone and low levels of corticosterone. However, the roosters that had acquired this high body weight were also at risk of having less complete copulations because of their physical mass. The loss of uniformity of the males and the appearance of hierarchies within the flock accompany a decline in the percentages of hatches as a consequence of the poor confirmation of the males for copulation or the restriction to the access to the females. Results of this study show that the decrease in fertility from 45 weeks of age has been associated with a decline in testicular weight, sperm production and the testosterone levels in animals with a sub-par weight. Likewise, decreasing hatch in older flocks may also result from a loss of conformation, and the lack of complete copulations is possible because of animals that are grossly overweight.

Relationships Between Fertility and Some Parameters in Male Broiler Breeders (Body and Testicular Weight, Histology and Immunohistochemistry of Testes, Spermatogenesis and Hormonal Levels)

Cloacal Gland and Gonadal Photoresponsiveness in Male Japanese Quail Selected for Divergent Plasma Corticosterone Response to Brief Restraint

Maternal Corticosterone Further Reduces the Reproductive Function of Male Offspring Hatched from Eggs Laid by Quail Hens Selected for Exaggerated Adrenocortical Stress Responsiveness

S. A. Castille

Papers

Cloacal Gland and Gonadal Photoresponsiveness in Male Japanese Quail Selected for Divergent Plasma Corticosterone Response to Brief Restraint

Maternal Corticosterone Further Reduces the Reproductive Function of Male Offspring Hatched from Eggs Laid by Quail Hens Selected for Exaggerated Adrenocortical Stress Responsiveness

Early T-maze behavior and broiler growth.

Cloacal Gland Growth Differences in High and Low Plasma Corticosterone Stress Response Line Male Quail Reared Under Short Daylengths

Struggling behavior in shackled male and female broiler chickens