Sacchi Roberto, Scali Stefano, Mangiacotti Marco, Sannolo Marco, Zuffi Marco A L, Pupin Fabio, Gentilli Augusto, Bonnet Xavier
Dipartimento di Scienze della Terra e dell'Ambiente, Università degli Studi di Pavia, I-27100 Pavia, Italy.
Museo Civico di Storia Naturale di Milano, Corso Venezia 55, I-20121 Milano, Italy.
Gen Comp Endocrinol. 2017 Jan 1;240:114-120. doi: 10.1016/j.ygcen.2016.09.012. Epub 2016 Sep 22.
Sexual steroids influence reproductive behaviours and promote secondary sexual traits. In male lizards, increasing levels of testosterone (T) bolster conspicuous colouration, stimulate territoriality, and trigger antagonistic interactions among rivals. Moreover, in colour polymorphic species, reproductive strategy, aggressiveness and T levels can differ between morphs. Therefore, T level is considered as an important mechanism that regulates the expression of colour polymorphism and sexual behaviours of males. But in the polymorphic territorial wall lizard (Podarcis muralis), a lack of relationship between morphs and aggressiveness challenges the notion that T plays such a role. To examine this issue, we compared adult T levels among three colour morphs (white, yellow and red) through repeated sampling during the mating season. High T levels were observed at the onset of the mating season followed by a significant decrease, a pattern documented in other lizard species. Mean T levels did not differ among morphs. However, yellow males maintained significantly higher T levels over time and displayed a stronger subsequent decline. Overall, in this species, seasonal T patterns differ among morphs, not mean values. Previous studies revealed that T suppresses the immune response; suggesting that a strong initial investment promoted by high T levels may trade-off against immunity (maintenance). Further experimental investigations are required to clarify the relationship between T and reproductive effort in polymorphic species that exhibit complex temporal pattern of T levels.
性类固醇影响生殖行为并促进第二性征的发育。在雄性蜥蜴中，睾酮（T）水平的升高会增强其显著的体色，刺激领地行为，并引发雄性之间的对抗性互动。此外，在具有颜色多态性的物种中，不同形态之间的生殖策略、攻击性和T水平可能存在差异。因此，T水平被认为是调节雄性颜色多态性和性行为表达的重要机制。但在多态性的领地壁蜥（Podarcis muralis）中，不同形态与攻击性之间缺乏关联，这对T发挥此类作用的观点提出了挑战。为了研究这个问题，我们在交配季节通过重复采样比较了三种颜色形态（白色、黄色和红色）成年个体的T水平。在交配季节开始时观察到较高的T水平，随后显著下降，这种模式在其他蜥蜴物种中也有记录。不同形态之间的平均T水平没有差异。然而，随着时间的推移，黄色雄性个体的T水平显著更高，且随后下降幅度更大。总体而言，在这个物种中，不同形态的T水平季节性模式存在差异，而非平均水平。先前的研究表明，T会抑制免疫反应；这表明高T水平促进的强烈初始投入可能会与免疫（维持）形成权衡。需要进一步的实验研究来阐明在呈现复杂T水平时间模式的多态性物种中，T与生殖投入之间的关系。
