Date of Award
Doctor of Philosophy
Chytridiomycosis is an infectious disease of amphibians caused by the fungus Batrachochytrium dendrobatidis (Bd), and it has played an important role in the worldwide decline of amphibians. My dissertation research examined the consequences of Bdinfections on tadpole feeding biomechanics and activity, pathogen transmission, and host immunology. The keratinized labial teeth of Bd-infected Fowler's Toad (Anaxyrus [=Bufo] fowleri) and Grey Treefrog (Hyla versicolor) tadpoles slipped off of surfaces on which they grazed and were in contact with an algal-covered surface for a shorter duration of time during each feeding cycle. During feeding trials, Bd-infected A. fowleri and H. versicolor tadpoles obtained significantly less food and were less active during feeding relative to non-infected tadpoles. Collectively, these data show that Bd-infected tadpoles are less efficient and less active while feeding and provide a potential mechanism for reduced growth and development in Bd-infected tadpoles of these species. In artificial ponds, A. fowleri tadpoles raised in the presence of Bd aggregated significantly more relative to controls, whereas H. versicolor aggregated significantly less. In addition, ponds with A. fowleri tadpoles supported higher Bd prevalences and infection intensities relative to ponds with H. versicolor, suggesting that aggregation behavior may impact intraspecific Bd transmission. Independent of species, tadpoles raised in the presence of Bd were smaller and less developed than tadpoles raised in disease-free conditions, even when Bd prevalence was low. Although A. fowleri tadpoles seem more susceptible to Bd and carry heavier infections, our results suggest that Bd can negatively impact larval life history traits associated with fitness. To test possible mechanisms related to differential Bd susceptibility, I raised Southern Leopard Frog (Lithobates sphenocephalus) tadpoles on diets that differed in their protein content. Tadpoles fed a low-protein diet had less effective immune responses (PHA-induced skin-swelling resonse and the ability of tadpole blood to kill E. coli), increased susceptibility to Bd, and were less developed relative to tadpoles fed a high-protein diet. However, the immune responses of tadpoles infected with Bd were similar, suggesting that neither T cell recruitment nor cytotoxicity of tadpole blood (i.e., PHA and bacterial killing ability, respectively) specifically inhibit Bd infections.
dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.
Venesky, Matthew Damien, "Dynamics of an Emerging Infectious Disease of Amphibians: From Individuals to Communities" (2011). Electronic Theses and Dissertations. 159.