DESPRAT Julia L.
Post-doctorant : E2C
Université Lyon 1
CNRS, UMR 5023 - LEHNA,
Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés
3, rue Raphaël Dubois - Bât. Darwin C
F-69622 Villeurbanne Cedex FRANCE
- (+33) 04 72 43 11 41
During my PhD, my studies concerned the steroids effects on the production and expression of both acoustic and visual sexual signals in Hyla arborea. I am interested in the effect of hormones on the behavior plasticity and physiology, notably in the context of the sexual selection.
The immunocompetence handicap hypothesis (ICHH) proposed by Folstad and Karter in 1992 suggested the ambiguity of the testosterone role (increasing sexual signal but decreasing immunocompetence) as a universal mechanism of the signal honesty.
In my first work (Desprat et al. 2015) we tested the ICHH on H. arborea. We demonstrated that both the acoustic and visual sexual signals were testosterone dependent. Surprisingly, testosterone did not provoke an immunosuppression. Indeed, testosterone-supplemented males with high body mass presented an immunoenhancement.
Testosterone has a strong effect on the expression of the acoustic signal (Desprat et al. 2015). From a physiological point of view, calling activity is particularly demanding for energy. During the breeding season, males have to alternate between calling and foraging behavior. The high testosterone levels and the caloric restriction of the breeding season could affect the mitochondrial functioning and the contractile properties of the trunk muscles responsible of the calling activity.
In my second work, we tested the testosterone and the caloric restriction on the trunk muscle of H. arborea for the first time at two levels: the muscular activity and the mitochondrial functioning. We demonstrated physiological relationships between fatigue muscle contractile properties and the bout duration of the call, and between the mitochondrial respiration and muscle contractile properties. Also, the caloric restriction affected the force and duration of the muscle contraction as well as the mitochondrial respiration.
The coloration of the male vocal sac is testosterone dependent (Desprat et al. 2015). Carotenoids are the colored pigments involved in the vocal sac coloration. Carotenoids are also known for their antioxidant actions in the immune system. As a limited resource, males have to balance carotenoids between strong visual sexual signals and immunocompetence. Hence, females avail this clue to access male condition. Blas et al. 2006 suggested that testosterone increase the bio-avaibility of carotenoids.
In a third work, we demonstrated that the composition in carotenoids was tissue dependent. Four carotenoids were identified to be specific of the vocal sac and the β carotene seemed to be the carotenoid form of the plasma. However, we did not find a testosterone effect on the carotenoid distribution between liver (storage organ), plasma and the vocal sac.
Associated with high testosterone levels both acoustic and visual signals also depend on foraging capacity, for energy and carotenoids supply respectively. Does testosterone influences the hunting performance, in order to be able to express powerful sexual signals?
We tested the testosterone effect on hunting behavior of H. arborea against a virtual cricket. We found that testosterone reduced the time before the first attack, compared to control males but this did not affect the attack success. However the effect of testosterone on the attack duration depends on the male body mass. Indeed, small testosterone-supplemented males had longer attack duration than small control males.
- Sous Presse Desprat, J.L., Lengagne, T., Mondy, N. Immune challenges and visual signaling in tree frogs. The Science of nature (Naturwissenschaften).2017 Desprat, J.L., Mondy, N., Lengagne, T., 2017 - Does testosterone affect foraging behavior in male frogs ? Hormones and Behavior, Hormones and Behavior, 90 : 25–30.2016 Lance, E., Desprat, J., Holbech, B.F., Gérard, C., Bormans, M., Lawtond, L.A., Edwards, C., Wiegand, C., 2016 - Accumulation and detoxication responses of the gastropod Lymnaea stagnalis to single and combined exposures to natural (cyanobacteria) and anthropogenic (the herbicide RoundUp® Flash) stressors. Aquatic Toxicology, 177 : 116–124.2015 Desprat, J.L., Lengagne, T., Dumet, A., Desouhant, E., Mondy, N., 2015 - Immunocompetence handicap hypothesis in tree frog: trade-off between sexual signals and immunity ? Behavioral Ecology, 26(4) : 1138–1146.2015 Josserand, R., Troïanowski, M., Grolet, O., Desprat, J.L., Lengagne, T., Mondy, N., 2015 - A phytohaemagglutinin challenge test to assess immune responsiveness of European tree frog Hyla arborea. Amphibia-Reptilia 36 : 111-118.
- Autres productions 2016 - Desprat, J.L. When Ecology and Behaviour meet: Introduction to the special section on the Ecology and Behaviour Meeting 2016.
Animal Biology 66 : 401–402.
- Desprat, J.L., 2016 - When Ecology and Behaviour meet: Introduction to the special section on the Ecology and Behaviour Meeting 2016. Animal Biology 66: 401–402.