Immune challenges and visual signalling in tree frogs
In animals, mate-choice is often based on sexual signals that carry information and help the receiver make the best choice to improve the receiver’s fitness. Orange visual sexual signals have been hypothesised to carry immune information because they are often due to carotenoid pigments which are also involved in immunity response. Although many studies have focused on the direct relationships between coloration and immunocompetence, few studies have simultaneously studied immunocompetent response and coloration variation after an immune challenge. We tested this hypothesis on starved and ad libitum-fed males of the European tree frog Hyla arborea. Our results show that male coloration is not a reliable indicator of its immune response capacity in this species. However, after an immune challenge induced by a PHA (Phaseolus vulgaris phytohaemagglutinin) injection, starved males presented a significant coloration loss and this alteration was related to the immune response intensity. Taken together, these results suggest that the brighter (lighter) coloration may be used as a cue by female to exclude males with a recent immune challenge, due to diseases or parasites for example.
KeywordsAmphibian Coloration Hyla arborea Immunocompetence Phytohaemagglutinin
The authors thank Adeline Dumet for the technical assistance and data collection during the experiments and Bernard Kaufmann for the English correction. JLD and NM contributed to the conception, design, data collection, interpretation of experiments, drafting and revision of the article. TL contributed to field work, drafting and revision of the article.
Compliance with ethical standards
We obtained the European certificate that legally allows us to design and conduct experimental research work using live animals, and all work was performed with the approval of the ethics committee of University of Lyon 1 (BH2012–15). Frogs were housed in the EcoAquatron of University of Lyon, which is a facility approved by Veterinary Services (approval number 692661201). All males were released to the original pond the night after the end of the experiments.
This work was supported by the French Ministry of Higher Education and Research (to J.L.D., PhD grant 2012–2015).
Conflict of interest
The authors declare that they have no conflict of interest.
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