Glucocorticoid metabolism in the in ovo environment modulates exposure to maternal corticosterone in Japanese quail embryos ( Coturnix japonica )

Abstract

Maternal effects have gained attention as a method by which mothers may alter the physiological condition and phenotype of their offspring based upon current environmental conditions. The physiological and phenotypic outcomes of glucocorticoid-mediated maternal effects have been extensively studied in a variety of vertebrates; however, the underlying mechanism is currently unclear. Here, we injected tritiated corticosterone into the yolks of freshly laid Japanese quail eggs (Coturnix japonica) and traced its movement and metabolism through the in ovo development period. We found that corticosterone was extensively conjugated throughout the egg by the end of development, and while minimal corticosterone was detected within the embryo during development, accumulation of a conjugated metabolite in the embryo started to occur on day 6 of development. Because no movement and metabolism of corticosterone occurred in infertile eggs, our findings suggest that embryos are not passive recipients of maternal steroids, but instead appear to possess extensive metabolic capabilities, which may modulate their exposure to maternal steroids.

Pre‐ and Postnatal Effects of Corticosterone on Fitness‐Related Traits and the Timing of Endogenous Corticosterone Production in a Songbird

“…Radiolabeled corticosterone injected into chicken eggs was found in embryonic tissue by day 6 of incubation. The steroid was in a conjugated, polarized form (von Engelhardt et al., ), which suggests that avian embryos may modulate the effects of maternally or experimentally derived corticosterone (Vassallo et al., ) and other steroids (Paitz et al., ) early during incubation. Although the fate of maternally deposited corticosterone in eggs and the role of its metabolites remain largely unexplored, there is little doubt that elevated prenatal levels of corticosterone can produce significant fitness‐related effects on the phenotype of altricial nestlings, effects that ultimately influence their success as fledglings and adults.…”

Immune Activation Generates Corticosterone-Mediated Terminal Reproductive Investment in a Wild Bird

“…Effects of yolk corticosterone on offspring phenotype appear to be decidedly mixed (Chin et al 2009; Love et al 2009; Henriksen et al 2011); however, we do know that developing avian embryos metabolize maternally derived steroids in eggs (von Engelhardt et al 2009; Paitz et al 2011; Paitz and Casto 2012; Vassallo et al 2014), and that, in our free-living study population, experimental elevation of corticosterone in the egg at laying enhances the post-hatching growth and asymptotic body mass of nestlings prior to fledging (Strange 2015), a trait positively associated with their long-term reproductive prospects (Bowers et al 2014 b ). It should be noted, however, that the specific mechanism through which in ovo corticosterone acts on offspring is unresolved and is likely to be more complex than traditionally thought (von Engelhardt et al 2009; Vassallo et al 2014). It should also be noted that experimental manipulations of yolk steroids can be problematic if they cause embryos to develop under concentrations of steroids other than what the maternal phenotype has been selected to produce.…”

Telomere dynamics may link stress exposure and ageing across generations

“…Interestingly, recent data also suggest that offspring are unlikely to be passive recipients of maternal glucocorticoids during embryonic development [67] and may temper parental stress effects. Regardless, while most evidence suggests that the effect of parental stress exposure on offspring telomeres is negative, it is important to remember that this is just one trait that can contribute to parental and offspring fitness.…”