Chytrid fungus (Batrachochytrium dendrobatidis) among amphibians in an Amazonian floodplain forest

Abstract

The increasing frequency of emerging infectious disease outbreaks is causing population declines and sparking concerns for species conservation. Chytridiomycosis is one of these diseases. It is caused by the widespread pathogenic fungus Batrachochytrium dendrobatidis (Bd) found on amphibians and is one of the leading causes of amphibian decline. The fungus has gained major attention for its role in decimating amphibian populations, particularly in upland forests in the neotropical realm, where the abiotic conditions are often ideal for the fungus. However, little is known about Bd prevalence and dynamics in the hotter lowland forests of the neotropics, particularly in the vast and remote areas of the Amazon lowlands. This study aims to improve our understanding of Bd prevalence in the Amazon lowlands, focusing specifically on a relatively unexplored area along the middle Juruá River in the western Brazilian Amazon. I conducted a survey where I assessed Bd prevalence in 23 anuran species (n = 95) at a single site in a floodplain forest along the middle Juruá river. The study area was approximately 44 km downstream from the town of Carauari in the state of Amazonas. Data on morphology (weight and snout-vent length), taxonomical identification and habitat preference were also collected to serve as potential predictors of Bd prevalence. Bd was detected in 7 anuran individuals, each belonging to a different species and representing six anuran families. The overall prevalence of Bd was 7.42 %. The low prevalence detected is consistent with most other findings from the few studies conducted in the Amazon lowlands. A logistic regression analysis showed no association between Bd infection and morphometrics or habitat preference (p > 0.05). This study is the first contemporary Bd survey along the Juruá river. It also adds a new species to the growing list of Bd-infected species worldwide, with the detection of an infected Pipa snethlageae individual. Large parts of the Amazon lowlands remain unexplored regarding Bd infection prevalence in amphibians and increased sampling will help us better understand Bd dynamics and its effects on amphibian populations.