Plumage colour and the expression of stress‐related genes in gull chicks

Abstract

In many bird populations, individuals show remarkable differences in feather colouration, which are often linked to individual differences in physiological traits, but the mechanisms maintaining this covariation are still unclear. Here, we investigate the variability of the melanic colouration in yellow‐legged gull Larus michahellis chicks. In this species, hatchlings show high variability in the number and colour intensity of black spots in their plumage. In gulls, last‐laid eggs receive less antioxidants but higher levels of androgens than first eggs. We first explored whether these remarkable differences within the clutch affect the feather melanisation during embryo development. Melanic colouration was not related to laying order, but nestling males were darker and had a larger spotted area than nestling females. In chicks hatching from first‐laid eggs, the spot size and spot lightness were negatively correlated. We also explored the effect of the developmental environment, through a cross‐fostering experiment, on the expression of five stress‐related genes (SOD2, ALKBH3, HSPA8, NLRC5 and TRIAP1) and their link with melanic colouration. Post‐hatching hierarchy did not affect the expression of any of the tested genes, but paler chicks showed reduced expression in some studied genes (SOD2, ALKBH3 and HSPA8) in comparison to darker chicks. Our results suggest that melanic chicks suffer less stress during development.

Redox-regulation and life-history trade-offs: scavenging mitochondrial ROS improves growth in a wild bird

“…Beta-actin gene ( ACTB ) was used as reference gene 66 , and gene-specific primers were designed using sequence information obtained from previously published sequences for ACTB , KIT , CASP7 , and SIRT1 genes in the yellow-legged gull 67 or using the available sequences in Charadriiformes (see Supplementary Methods and Table S5). The level of expression was measured in a 20 µl reaction volume, and all reactions were performed in duplicate (see details in Supplementary Methods).…”

Emerging Genetic Tools to Investigate Molecular Pathways Related to Heat Stress in Chickens: A Review

“…Another important feature of the plumage is the color of feathers, which can impact the ability of chickens to respond under HS conditions. A recent study demonstrated that dark chicks showed a lower expression rate of genes belonging to pathways of stress (cellular stress: SOD2 and HSPA8 ; DNA damage repair: ALKBH3 ) than paler chicks [ 74 ]. This happens because the plumage element reduced solar heat gain by 5% in both light and dark plumages.…”

Melanin‐based sexual dichromatism in the Western Palearctic avifauna implies darker males and lighter females

“…We do not intend to describe all dichromatisms in the birds of the Western Palearctic, but to test for the direction of the difference in the hues of visible wavelengths for melanin pigments in adult males and females. In this regard, we did not consider sexual dichromatisms in juvenal plumages, such as the one recently described for the yellow-legged gull Larus michahellis, in which male chicks have larger spotted areas and darker spots in the head than female chicks (Diaz-Real et al 2017). This sex-specific coloration is noticeable as the adult birds are monochromatic.…”