Date of Award

5-31-2022

Document Type

Campus Access Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Douglas C. Woodhams

Second Advisor

Luis F. De León

Third Advisor

Mayra C. Vidal

Abstract

The skin of amphibians harbors a variety of immunological defenses that change through life history. Interactions between skin defenses play a vital role in host health, development and immunological adaptations. Mucosal secretions contain defense compounds that can contribute to host defense against infection. Amphibian populations worldwide have been experiencing population declines due to the emerging fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal), which can cause the disease chytridiomycosis. Disease-induced population declines in amphibians are thought to be modulated by physiological and immunological responses, since some populations show disease resilience. One hypothesized driver of host-pathogen coexistence is immunomodulation during development such that frogs exposed to Bd in early life stages can gain tolerance to infection that persists through metamorphosis, even upon re-exposure. I tested this with Northern leopard frogs (Lithobates pipiens) exposed to Bd as tadpoles and examined them for disease resistance upon re-exposure as metamorphs. My results suggest that survival rates tended to be higher in non-exposed frogs (92% survival) compared to frogs exposed as tadpoles (81% survival). Thus, early Bd exposure did not affect survivorship and mortality was lower than expected. In addition, we tested the influence of peptide depletion on vulnerability towards Bsal. Frogs did not become infected; but their peptide composition and abundance were altered by the exposure. In addition, antimicrobial skin peptides Brevinin-1Pa and Brevinin-1Pb were detected. These peptides are known to have antifungal properties and help with Bd inhibition. Continued discovery of mechanisms of resilience to disease emergence in amphibian populations is critical to conservation and disease mitigation.

Comments

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