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.在诸多鸟类种群中，个体间的羽毛着色存在显著差异，这类差异通常与个体生理特征的差异相关联，但维持这种共变异的机制仍未阐明。本研究针对黄腿银鸥（Larus michahellis）雏鸟的黑色素着色变异特征展开探究。该物种的刚出壳雏鸟，其羽毛上黑斑的数量与颜色深浅均存在较高变异度。在鸥类中，相较于首枚产卵，最后产出的卵所含抗氧化剂更少，但雄激素水平更高。我们首先探究了一窝卵内的这种显著差异是否会影响胚胎发育阶段的羽毛黑色素沉着过程。研究发现，黑色素着色与产卵顺序并无关联，但雄性雏鸟的体色更深，且黑斑总面积大于雌性雏鸟。在从首枚卵孵化出的雏鸟中，黑斑尺寸与黑斑亮度呈负相关关系。本研究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。结果显示，孵化后的等级地位并未对所有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，黑色素沉着程度更高的雏鸟在发育过程中承受的应激压力更小。