Defense Date

4-28-2022

Graduation Date

Summer 8-13-2022

Availability

One-year Embargo

Submission Type

dissertation

Degree Name

PhD

Department

Biological Sciences

Committee Chair

Sarah Woodley

Committee Member

Brady Porter

Committee Member

Wook Kim

Committee Member

Corinne Richards-Zawacki

Keywords

amphibian, chytridiomycosis, immunology, antimicrobial peptides

Abstract

A recently emerged chytrid fungal pathogen, Batrachochytrium salamandrivorans (Bsal) threatens salamander biodiversity. Bsal susceptibility varies between and within salamander species, but little is known about the mechanisms underlying these differences. Susceptibility is likely influenced by numerous interacting factors, but my dissertation studied the role of host immune responses.

My first aim investigated between species differences by studying the bioactive properties of salamander skin peptides against Bsal and the related pathogen, B. dendrobatidis (Bd). Skin peptides were collected from five salamander species, used for in vitro assays, and analyzed by RP-HPLC. While skin peptides from one species prevented Bsal and Bd growth entirely, those from other species either partially inhibited or did not inhibit Bsal and/or Bd growth. This suggests that skin peptides may protect some species from disease while serving alternative functions in others. Further, skin peptide defenses may not be equally effective against Bsal and Bd.

My second aim investigated within species differences by the studying the effects of corticosterone (CORT, stress bioindicator) and captivity on immunity and behavior of a single salamander species. After experimentally elevating CORT for variable time periods, I did not find any effect of CORT on immunity or behavior. While this contradicts previous work, animals used in this study were initially infected by Bd and had drastically lower Bd infection loads at the end of the experiment. This suggests that animals were actively fighting Bd infections. I hypothesize that Bd-immune interactions desensitized animals to CORT effects. Alternatively, immune responses may be decoupled from CORT.

Language

English

Additional Citations

Pereira KE, Cava K, and Woodley SK. 2021. An evaluation of immersive and handling methods for collecting salamander skin peptides. Journal of Herpetology 55(4), 318 -324.

Pereira, KE, and Woodley SK. 2021. Skin defenses of North American salamanders against a deadly salamander fungus. Animal Conservation 24(4), 552 -567.

Pereira KE, Crother BI, Sever DM, Fontenot CL, Pojman JA, Wilburn DB, and Woodley SK. 2018. Skin glands of an aquatic salamander vary in size and distribution and release antimicrobial secretions effective against chytrid fungal pathogens. Journal of Experimental Biology 221: jeb183707. Highlighted research article; also featured in Herpetological Review 49(3), 600-601.

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