Batrachochytrium dendrobatidis, an aquatic fungal pathogen causing chytridiomycosis resulting in both the keratinization of the permeable skin of adult amphibians as well as the dekeratinization and breakdown of the beak and denticles of larval individuals, has caused a drastic decline in amphibian populations worldwide.  This study focuses on its occurrence in the Rara avis reserve of Costa Rica, mapping its distribution through the analyses of approximately 800 tadpole samples.  Correlation of location, species, and extent of development has shown that tadpoles, mostly in the G25 stage on the Gosner scale of development, display the greatest affinity for infection at larger sizes. In other words, amphibian species whose larvae spend the longest duration in an aquatic environment are at the greatest risk of infection.  This occurrence, specifically within the species Rana warszewitschi which shows high survivability despite infection, suggests that they could act as reservoirs for the pathogen.   As a result of the area’s landscape it is unlikely that the tadpoles also serve as vectors for the pathogen.  However, the movement of infected metamorphs that survive to maturity may account for this spreading pattern.  Future research will investigate this theory, exploring the relationship between vector and sink necessary for the transmission of chytrid zoospores.

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