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Effects of climate change on the immune defenses and disease susceptibility of amphibian hosts

Saenz Calderon, Veronica (2021) Effects of climate change on the immune defenses and disease susceptibility of amphibian hosts. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Abstract

Many amphibians metamorphose in ephemeral ponds that are sporadically filled with rain and then desiccate at differential drying rates. Climate change is predicted to alter water temperature, precipitation, and humidity, which will ultimately alter the conditions of ephemeral breeding ponds. The decreased water availability causes stress on amphibians, usually resulting in a faster metamorphosis. In this experiment, tadpoles of the Northern leopard frog (Rana pipiens) exposed to desiccation did not metamorphose faster but had lower survival and mass after metamorphosis. I hypothesized that developing in a drying pond would negatively impact the development of immune defenses important to defense against fungal pathogen Batrachochytrium dendrobatidis (Bd) and increase susceptibility to this pathogen after metamorphosis. However, after experimental exposure to Bd, I did not find a direct effect of drying on pathogen load or probability of infection. Yet, mass at metamorphosis and post-metamorphic growth rate, both of which were affected by drying, did impact the Bd infections that exposed animals developed. Frogs that were smaller at metamorphosis, as was more often the case when they developed in drying conditions, had greater Bd loads, and the frogs exposed to the fastest drying had lower survival after Bd exposure than the frogs in the no drying treatment. There were no significant direct effects of drying on the immune parameters I measured after the Bd-exposure experiment, but sham exposed frogs had a greater amount and diversity of antimicrobial peptides in their skin mucus than did the Bd exposed frogs. Overall, our results indicate that developing in a drying pond can directly affect size and survival even in the absence of changes in larval period. In addition, developing in a drying pond appears to indirectly impact pathogen load and survival for animals exposed to Bd. These findings contribute to a better understanding of the direct and indirect effects of stress during early development on amphibian immune function, and better predict how amphibian populations will fare in a changing climate.


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Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Saenz Calderon, Veronicaves24@pitt.eduves24
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee MemberCarlson, Anneacarlson@pitt.edu
Committee MemberBoyle, Jon Pboylej@pitt.edu
Committee MemberKohl, KevinKKOHL@pitt.edu
Committee MemberRollins-Smith, Louiselouise.rollins-smith@Vanderbilt.Edu
Committee ChairRichards-Zawacki, Corinnecori.zawacki@pitt.edu
Date: 8 October 2021
Date Type: Publication
Defense Date: 15 June 2021
Approval Date: 8 October 2021
Submission Date: 23 July 2021
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 333
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Batrachochytrium dendrobatidis, immunity, climate change, drying, temperature, ephemeral, permanent
Date Deposited: 08 Oct 2021 19:40
Last Modified: 08 Oct 2021 19:40
URI: http://d-scholarship.pitt.edu/id/eprint/41761

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