Sex-specific effects of the in ovo environment on early-life phenotypes in eiders

Abstract

Maternal effects affect offspring phenotype and fitness. However, the roles of offspring sex-specific sensitivity to maternal glucocorticoids and sex-biased maternal investment remain unclear. It is also uncertain whether telomere length (a marker associated with lifespan) depends on early growth in a sex-specific manner. We assessed whether maternal traits including corticosterone (CORT; the main avian glucocorticoid) and in ovo growth rate are sex-specifically related to offspring CORT exposure, relative telomere length (RTL) and body condition in eiders (Somateria mollissima). We measured feather CORT (fCORT), RTL and body condition of newly hatched ducklings, and growth rate in ovo was expressed as tarsus length at hatching per incubation duration. Maternal traits included baseline plasma CORT, RTL, body condition and breeding experience. We found that fCORT was negatively associated with growth rate in daughters, while it showed a positive association in sons. Lower offspring fCORT was associated with higher maternal baseline plasma CORT, and fCORT was higher in larger clutches and in those hatching later. The RTL of daughters was negatively associated with maternal RTL, whereas that of males was nearly independent of maternal RTL. Higher fCORT in ovo was associated with longer RTL at hatching in both sexes. Duckling body condition was mainly explained by egg weight, and sons had a slightly lower body condition. Our correlational results suggest that maternal effects may have heterogeneous and even diametrically opposed effects between the sexes during early development. Our findings also challenge the view that prenatal CORT exposure is invariably associated with shorter telomeres.

Disentangling relationships between physiology, morphology, diet, and gut microbial diversity in American kestrel nestlings

“…Because of their implications for host health and development, gut microbial composition and diversity may have profound impacts on the developmental trajectory of phenotypic traits related to individual fitness (Mitchell et al 2013, Burton and Metcalfe 2014, Öst et al 2020). Within birds, individual variation in nestling development has been well documented, and in many cases linked to variation in ecological conditions such as lay date (McKinnon et al 2012, Samplonius et al 2016, Cornell and Williams 2017), interannual variation (Kaliński et al 2015, Markowski et al 2015), weather and temperature patterns (Ardia 2013, Rodríguez and Barba 2016, de Zwaan et al 2020), food availability, or parental provisioning rate (Merino and Potti 1998, Forero et al 2002, Scheuerlein and Gwinner 2006).…”

Egg corticosterone can stimulate telomerase activity and promote longer telomeres during embryo development

“…In wild birds, there is some evidence suggesting a positive link between maternal GCs and offspring telomere length. A recent study in eiders ( Somateria mollissima ) found that higher egg corticosterone is associated with longer telomeres at hatching (Öst et al., 2020), suggesting that in natural conditions maternal GCs may help to upregulate telomere lengthening mechanisms during prenatal development. Indeed, telomerase activity seems to be maintained throughout the life in long‐lived birds (Haussmann et al., 2007) and mild increases in GCs levels have also been associated to an up‐regulation of telomerase activity, at least in humans (Epel et al., 2010).…”

Breeding under pressure: Corticosterone is associated with reproductive investment under fluctuating predation risk in a long‐lived sea duck

“…Samples were centrifuged and blood serum was stored at −20°C until CORT radioimmunoassay was carried out at the Centre d'Etudes Biologiques de Chizé (mean inter‐assay coefficient of variability (CV): 13.66%, mean intra‐assay CV: 8.98%). This radioimmunoassay method is further detailed in Supplementary Material S3 and has been validated for the study population (Mohring et al, 2021; Öst et al, 2020). As baseline CORT levels (in ng/mL) did not significantly increase with sampling time (linear regression of baseline CORT levels on sampling time, including year to control for interannual variation in baseline CORT levels: t = 0.82, p = 0.41) and as all samples were taken within 3 min (Romero & Reed, 2005), they were considered to reflect baseline levels and hence we did not include sampling time in the following statistical analyses.…”