High temporal and individual variation in the prevalence and intensity of chytrid infection in the southernmost Leaf Frog of the genus Pithecopus (Anura, Phyllomedusidae)

Pithecopus rusticus is an endemic amphibian restricted to the type locality, in southern Brazil, and possibly endangered to extinction, due to habitat degradation. However, an additional threat to amphibians is the chytrid fungus, which has been associated with amphibian population declines and extinctions. Hence, we tested the hypothesis that Batrachochytrium dendrobatidis (Bd) prevalence and infection load varies temporally and individually in P. rusticus , due to the influence of climatic and intrinsic individual factors. We swabbed adult individuals during two breeding seasons. Bd prevalence and infection load differed between breeding seasons and sampled months. In the middle of the first season, we found a peak of Bd load followed by a significant decrease. Only one infected individual was found in the middle of the second breeding season. Bd load was related to air temperature and rainfall, and individuals with lower scaled mass index had higher infection load. We showed that Bd incidence is highly variable in the same wild frog population. The temporal and individual decrease in zoospore load may suggest that P. rusticus can reverse high infection levels, and this may be evidence of efficient immunological responses present in this leaf frog.