title: Does physiological response to disease incur cost to reproductive ecology in a sexually dichromatic amphibian species?
abstract: It is well known that the disease chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd) has contributed to amphibian declines worldwide. The impact of Bd varies, with some species being more susceptible to infection than others. Recent evidence has shown that Bd can have sub-lethal effects, whereby increases in stress hormones have been associated with infection. Could this increased stress response, which is a physiological adaptation that provides an increased resilience against Bd infection, potentially be a trade-off with important life-history traits such as reproduction? We studied this question in adult male frogs of a non-declining species (Litoria wilcoxii). Frogs were sampled for (1) seasonal hormone (testosterone and corticosterone), color and disease profiles, (2) the relationship between disease infection status and hormone levels or dorsal color, (3) subclinical effects of Bd by investigating disease load and hormone level, and (4) reproductive and stress hormone relationships independent of disease. Testosterone levels and color score varied seasonally (throughout the spring/summer months) while corticosterone levels remained stable. Frogs with high Bd prevalence had significantly higher corticosterone levels and lower testosterone levels compared to uninfected frogs, and no differences in color were observed. There was a significant positive correlation between disease load and corticosterone levels, and a significant negative relationship between disease load and testosterone. Our field data provides novel evidence that increased physiological stress response associated with Bd infection in wild frogs, could suppress reproduction by down-regulating gonadal hormones in amphibians, however the impacts on reproductive output is yet to be established.
authors.affiliation: Environmental Futures Research Institute, School of Environment, Griffith University, Gold Coast campus, QLD 4222, Australia. Electronic address: christina.kindermann@griffithuni.edu.au.
authors.forename: Christina
authors.initials: C
authors.lastname: Kindermann
authors.affiliation: Environmental Futures Research Institute, School of Environment, Griffith University, Gold Coast campus, QLD 4222, Australia; School of Animal and Veterinary Sciences, Faculty of Science, Charles Sturt University, Wagga Wagga, NSW 2678, Australia.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Narayan
authors.affiliation: Environmental Futures Research Institute, School of Environment, Griffith University, Gold Coast campus, QLD 4222, Australia.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Hero
mesh_terms: D000818:Animals; D001001:Anura / Q000382:microbiology / Q000502:physiology* / Q000652:urine; D015415:Biomarkers / Q000652:urine; D008411:Chytridiomycota / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology*; D003345:Corticosterone / Q000652:urine; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D054884:Host-Pathogen Interactions; D008297:Male; D011793:Queensland; D012098:Reproduction; D045483:Rivers; D012621:Seasons; D012867:Skin / Q000378:metabolism / Q000382:microbiology; D013312:Stress, Physiological; D013739:Testosterone / Q000652:urine
chemical_list: D015415:Biomarkers; D013739:Testosterone; D003345:Corticosterone
keywords: Batrachochytrium dendrobatidis; Breeding colors; Conservation physiology; Physiological adaptation; Reproductive ecology; Stress