Pathogenicity of Batrachochytrium dendrobatidis in larval ambystomatid salamanders


Chytridiomycosis is a disease of amphibians caused by the fungus Batrachochytrium dendrobatidis (Bd), which colonizes keratinized tissues in adult and larval amphibians. Considerable progress has been made in understanding the host-pathogen ecology of Bd in larval anurans, yet little is known about how Bd affects larval salamanders. Because the structure of keratinized jaw sheaths in Ambystoma larvae have not been thoroughly documented, we first described the structure in three species of larval Ambystoma. We then conducted a laboratory experiment to test if Bd affects growth and developmental rates of larval Marbled Salamanders (Ambystoma opacum). We observed keratinized jaw sheaths in all three species of Ambystoma, but the sheath was not present in all individuals. In our exposure experiment, none of the A. opacum, whose mouthparts were screened for Bd, tested positive, nor was there an effect of Bd on larval life-history responses. A cautionary note, however, is that although our method of Bd infection has been successful in other amphibian-Bd experiments in our laboratory, our exposure experiment did not include a positive control of other taxa known to become infected with Bd. We are uncertain why none of the larval A. opacum became infected with Bd, given that we observed keratinized jaw sheaths in this species. Two possible explanations are the keratinized jaw sheaths of larval Ambystoma differ among species in structure or keratin type so that Bd may not be able to successfully infect them or, A. opacum larvae may have cleared low intensity Bd infections prior to metamorphosis.

Publication Title

Herpetological Conservation and Biology

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