Biology subjects

Beziers, P.

Publications and source records attributed to Beziers, P..

3 recordsLinked to original sources

bioRxiv2019

Survival of adult barn owls is linked to corticosterone levels

Glucocorticoid hormones, such as corticosterone, are fundamental in the translation of external stimuli into physiological adjustments that promote the survival of an organism in face of changes in its environment. At baseline levels, corticosterone is crucial in regulating daily life metabolism and energy expenditure, whereas the acute corticosterone response promotes short-term physiological and behavioral responses to unpredictable environmental challenges. Given their different physiological effects and their role in mediating fitness components, it is still unclear whether and how inter-individual variation in baseline corticosterone levels and acute stress-response levels can affect the survival of organisms. We used 13 years of capture-recapture and dead recovery data combined with 11 years of corticosterone measurements taken on breeding barn owls (Tyto alba) to investigate how survival probability varies in relation to baseline and stress-induced corticosterone levels. Our study shows that males with a higher level of both baseline and stress-induced corticosterone levels have a higher probability of surviving than individuals with lower corticosterone levels. In females, survival probability was higher in individuals presenting elevated stress-induced corticosterone levels but was not significantly associated to baseline corticosterone levels. Our results suggest that in the barn owl the stress-induced corticosterone response is a better proxy of adult survival than baseline corticosterone levels. Further studies investigating the link between corticosterone levels and different fitness components as well as the environmental factors (e.g. weather, development conditions, disease and predation risk) leading to such endocrine phenotypes are needed to identify the costs and benefits of presenting high and low corticosterone profiles.

evolutionary biology↗

bioRxiv2019

Reproductive success in the barn owl is linked to partner compatibility in glucocorticoid levels

In biparental species, reproductive success depends not only on the quality of the parents, the care they each provide and many environmental factors such as territory quality and food availability, but also on the ability of the parents to collaborate and divide reproductive tasks. Because hormones, such as corticosterone (CORT), modulate physiological and behavioural functions that are associated to reproductive success, hormonal compatibility between pair members is likely to have consequences on reproductive success. Here, we investigated in the barn owl (Tyto alba) whether baseline and stress-induced CORT levels are correlated between breeding partners and whether this correlation is associated to fitness parameters (i.e., clutch size, offspring number and body mass). We found that the combination of CORT levels in the two partners predicts reproductive parameters. Pairs with similar baseline CORT levels during incubation produced more fledglings than pairs with dissimilar baseline CORT levels. On the other hand, pairs showing dissimilar stress-induced CORT responses during the period of offspring rearing produced more fledglings than pairs with similar stress-induced responses. Offspring body mass was associated only with maternal (baseline and stress-induced) CORT levels and depended on the context with baseline CORT being potentially adjusted to environmental conditions but also to the energetic demand of reproduction. Hence, to produce large broods good quality mothers might increase their baseline CORT to meet the energetic demand of the brood, while mothers in unfavourable habitats may have smaller broods but still need to increase baseline CORT to cope with the environmental challenges. Taken together, the results show that the association between parental CORT levels and reproductive success are context-dependent and rely on the combination of parental CORT levels. Assuming that CORT levels reflect investment in parental care, our study suggests that parents coordinate their reproductive activities in a complex way to ensure a high reproductive success.

evolutionary biology↗

bioRxiv2019

Expression of glucocorticoid and mineralocorticoid receptor genes co-vary with a stress-related colour signal in barn owls

Glucocorticoid hormones are important intermediates between an organism and its environment. They enable an organism to adjust its behavioural and physiological processes in response to environmental changes by binding to mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) expressed in many tissues, including the integument. The regulation of glucocorticoids covaries with melanin-based colouration in numerous species, an association that might result from the melanocortin system and evolve within a signalling context. Most studies have focused on the circulating levels of glucocorticoids disregarding the receptors that mediate their action and could partly account for the covariation between the regulation of stress and melanin-based coloration. We investigated the association between melanin-based coloration and the gene expression levels of GR and MR but also of the melanocortin system and melanogenesis in the growing feathers of nestling barn owls (Tyto alba). We also considered the expression of genes related to the melanocortin system and melanogenesis to better understand the origin of the link between the expression of receptors to which corticosterone binds and melanin-based coloration. Nestling barn owls displaying larger black feather spots expressed GR and MR at lower levels than did smaller-spotted individuals. Because the expression of the GR and MR genes was positively, rather than negatively, correlated with the expression of melanogenic genes, we suggest that the link between melanin-based coloration, GR and MR is not directly associated to melanogenesis. The finding that the expression of GR and MR was positively associated with the expression of the PCSK2 gene (encoding the protein convertase responsible for post-translational modification of the proopiomelanocortin hormone) suggests that the melanocortin system may be implicated in the establishment of the covariation between melanism and the expression of receptors to which glucocorticoids bind. Together with previous studies, our results suggest that coloration is not only related to the production of glucocorticoids but also to the sensitivity of the integument to glucocorticoids.

physiology↗