Effects of salinity on amphibian disease outcomes

Dugan, Mitchell

Effects of salinity on amphibian disease outcomes

Persistent URL

https://hdl.handle.net/10456/59172

Author(s)

Dugan, Mitchell

Date Issued

April 1, 2025

Abstract

One important contaminant that is affecting freshwater ecosystems and the wildlife living in them is salt used to deice roads. Salt can act as an energetic stressor on amphibians, as they could struggle to osmoregulate themselves and maintain ion balance. Amphibian kidneys are adapted to conserve ions by producing diluted urine. Increases in ions can be taxing as amphibians try to rid themselves of excess ions. Salinity can also trigger a stress response which typically helps amphibians cope with the stimuli. But when the stress response is active for too long, it can be harmful to individuals, seen in a decrease in immune function, which can cause animals to be more susceptible to disease. It is unclear whether salt is acting as a stressor and harming amphibian disease outcomes, or if salt is having positive effects on disease outcomes. To investigate this, Xenopus laevis adult frogs were exposed to the fungal pathogen Batrachochytrium dendrobatidis (Bd) and housed in three possible salt treatments: no salt (0 mOsm/L NaCl), low salt (235 mOsm/L NaCl), and high salt (340 mOsm/L NaCl). It was hypothesized that frogs in the highest salinity treatment would have the highest Bd load and worst outcomes from disease. qPCR results revealed that no frogs were infected with Bd. Based on these results, my hypothesis could no longer be investigated, but instead I looked into how salinity and Bd exposure affected the survival of frogs. Salinity and Bd exposure both had statistically significant effects on frog survival; however, no interaction between salt and Bd on frog survival was observed. Frogs in the highest salinity group had a 0% survival, while frogs in the other two groups both had 100% survival. My conclusion based on my results was that sudden exposure to high salt could cause mortality, in contrast with the same level being survivable after gradual acclimation over time. The Bd exposed group had a 68% survival rate while the non exposed group had a 63.2% survival rate. Further studies are needed to understand the implications of my findings regarding salt and mortality, as well as to form a connection between these effects of salinity and amphibian disease outcomes.

Major

Biology

Honors

Biology, 2025

First Reader(s)

Venesky, Matthew D.