How Previous Stressors Affect Disease Resistance in Red-Backed Salamanders

Collins, Sean

How Previous Stressors Affect Disease Resistance in Red-Backed Salamanders

Persistent URL

http://hdl.handle.net/10456/46048

Author(s)

Collins, Sean

Date Issued

April 2018

Abstract

External climate factors influence the rate of physiological processes in ectotherms, and thus greatly influences their day to day actions. Not only does temperature affect the efficiency of their physiological processes, but it can also elevate an organism’s stress levels. With an increasingly changing climate, ectotherms are going to be put out of their optimal range for their physiology more often, causing more and more stress. Corticosterone (hereafter CORT) is a main hormone of the stress response in amphibians that may help them survive a particular situation and has been shown to have immuno-suppressing effect, when chronically elevated. My experiment examined how stress affects disease resistance, using two separate lab experiments, a control temperature group and a high temperature group, and a No CORT group and CORT group. I used the amphibian chytrid fungus, Batrachochytrium dendrobatidis (hereafter Bd), a fungal pathogen that may be responsible for many worldwide amphibian population declines. After a 10-day period the stressors were stopped, every animal was housed at the same temperature, and I exposed every animal to an infectious dose and Bd. There was no difference in mass loss during the stress period between the CORT and No CORT group, but the CORT group did lose significantly more mass than the No CORT group following the Bd exposure. The high temp group lost significantly more mass following the 10 day temperature exposure period compared to the low temp group, and the low temp group lost significantly more mass following the exposure to Bd. I found no statistically significant differences in infection abundance post treatment between the CORT/ No CORT groups and the Low Temp/High Temp groups. My results suggest that the established protocol the CORT dosing cycle I used may not cause the immediate physiological changes in metabolic rate or the immune response. My results also suggest that if an ectotherm experiences a temperature increase, that doesn’t put them out of their preferred temperature range, their physiological processes could be enhanced in the short term allowing them to be better prepared for an impending infection. Future studies that build of this one could add a sham Bd component with same treatment groups and same timeline, with an ELISA both after the stress period and post Bd exposure. In order better understand the long-term effects of stress on body condition, circulating CORT and disease resistance.

Major

Biology

First Reader(s)

Venesky, Matthew D.