# Dynamic effects of thermal acclimation on chytridiomycosis infection intensity and transmission potential in Xenopus laevis

## TL;DR

This study explores how temperature changes affect the severity of a deadly amphibian disease in frogs, finding that delayed thermal acclimation can lead to higher infection intensity.

## Contribution

The study reveals the dynamic and persistent effects of thermal acclimation on Bd infection intensity and clarifies its limited impact on transmission.

## Key findings

- Warm-acclimated frogs exposed to Bd after a temperature decrease had higher infection intensities.
- Thermal acclimation effects on infection intensity persisted for up to five weeks.
- Thermal acclimation did not affect zoospore production, suggesting no impact on transmission.

## Abstract

The pandemic amphibian pathogen Batrachochytrium dendrobatidis (Bd) can cause more severe infections with variable temperatures owing to delays in host thermal acclimation following temperature shifts. However, little is known about the timing of these acclimation effects or their consequences for Bd transmission. We measured how thermal acclimation affects Bd infection in Xenopus laevis, using a timing-of-exposure treatment to investigate acclimation effect persistence following a temperature shift. Consistent with a delay in host acclimation, warm-acclimated frogs exposed to Bd immediately following a temperature decrease (day 0) developed higher infection intensities than frogs already acclimated to the cool temperature. This acclimation effect was surprisingly persistent (five weeks). Acclimation did not affect infection intensity when Bd exposure occurred one week after the temperature shift, indicating that frogs fully acclimated to new temperatures within 7 days. This suggests that acclimation effect persistence beyond one week post-exposure was caused by carry-over from initially high infection loads, rather than an extended delay in host acclimation. In a second experiment, we replicated the persistent thermal acclimation effects on Bd infection but found no acclimation effects on zoospore production. This suggests that variable temperatures consistently exacerbate individual Bd infection but may not necessarily increase Bd transmission.