Immune challenges and visual signalling in tree frogs
Abstract
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 im- mune information because they are often due to caroten- oid pigments which are also involved in immunity re- sponse. Although many studies have focused on the direct relationships between coloration and immunocompetence, few studies have simultaneously studied immunocompe- tent 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 inten- sity. 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.