DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03828

ABSTRACT: Thermal acclimation effects on locomotory performance have been widely documented for macroscopic organisms, but such responses remain largely unexplored in microorganisms. Metabolic theory of ecology (MTE) predicts faster responses in smaller organisms, with potential consequences for host-parasite interactions in variable temperature environments. We investigated thermal acclimation effects on zoospores from the amphibian fungal pathogen Batrachochytrium dendrobatidis (Bd), quantifying (1) thermal performance for maximum zoospore velocity and (2) high temperatures needed to immobilize 50% ( EMBED Equation.DSMT4 ) or 100% ( EMBED Equation.DSMT4 ) of zoospores. We obtained measurements within 18 minutes following a temperature shift. We found significant curvilinear acclimation effects on maximum zoospore velocity and  EMBED Equation.DSMT4 , though the latter pattern might have been driven by confoundment with zoospore density. We also observed a significant positive effect of the trial start temperature on  EMBED Equation.DSMT4 , consistent with a rapid acclimation response to the start temperature on a time scale of ~1–6 minutes (i.e., too rapid for our experimental acclimation treatments to detect), implying that zoospores either have constitutive heat tolerance (i.e., no acclimation) or fully acclimate  EMBED Equation.DSMT4  to new temperatures within ~10 minutes. To explore the plausibility of such a rapid response, we analyzed published  EMBED Equation.DSMT4  acclimation times for macroscopic eukaryotes, resulting in a predicted interquartile range of 3.11–25.98 minutes when mass scaled to the size of a Bd zoospore. Taken together, these results suggest that Bd zoospores do exhibit thermal acclimation response on the rapid time scale predicted by MTE, possibly giving Bd an advantage over slower-acclimating hosts in variable temperature environments.