Data from: Plumage colour and the expression of stress-related genes in gull chicks

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.在众多鸟类种群中，个体间的羽毛着色存在显著差异，这类差异往往与个体生理特征的差异相关联，但维持这种协变关系的具体机制仍未明确。本研究聚焦黄腿鸥（yellow-legged gull, Larus michahellis）雏鸟的黑色素着色（melanic colouration）变异情况。该物种的雏鸟体羽上的黑色斑点数量与颜色饱和度均存在较高变异性。在鸥类中，相较于首枚产卵，末枚产卵的抗氧化物质含量更低，但雄激素水平更高。我们首先探究了同窝卵间的上述显著差异是否会影响胚胎发育阶段的羽毛黑色素沉着。黑色素着色与产卵顺序并无关联，但雏鸟雄性个体的羽毛颜色更深，斑点面积也大于雌性雏鸟。在首枚产卵孵化出的雏鸟中，斑点尺寸与斑点亮度呈负相关关系。我们还通过交叉抚育实验，探究了发育环境对5种应激相关基因（SOD2、ALKBH3、HSPA8、NLRC5及TRIAP1）表达量的影响，以及这些基因与黑色素着色之间的关联。孵化后的巢内等级并未对任何受试基因的表达量产生影响，但相较于体色更深的雏鸟，体色较浅的雏鸟在部分研究基因（SOD2、ALKBH3及HSPA8）上的表达量更低。本研究结果表明，黑色素着色程度更高的雏鸟在发育过程中承受的应激更少。