Meeting Abstract
Thermal acclimation responses in sheepshead minnow, Cyprinodon variegatus, were quantified by transfer, and reciprocal transfer, of fish between 11.1 and 18.2 C, 18.2 and 25.7 C, or 25.7 and 32.8 C. Changes in thermal acclimation status were assessed by post-transfer, time-series determinations of thermal tolerance (i.e. critical thermal minima and maxima). In general, heat tolerance gain and loss was complete in 20 and 25 days, respectively. Cold tolerance gain was achieved ca. 24 days post-transfer, but attrition was complete after only 12 to 13 days. Heat tolerance was gained asymmetrically, with fish acquiring approximately one-half of their accruable tolerance at the lowest transfer temperature. Likewise, the majority of cold tolerance accruement occurred during the warmest temperature transfer. Relatively uniform losses of heat and cold tolerance were seen in reciprocal transfers. Acclimation patterns were related to initial acclimation temperature, final acclimation temperature, and acclimation time, and could be accurately modeled by multiple linear regression. The results suggest that sheepshead minnow accrue a majority of their high or low temperature tolerance early in the acclimation process well before potential damaging temperatures are likely to occur. This novel pattern of asymmetric heat and cold tolerance acquisition in sheepshead minnow may be a key adaptation for surviving rapid and unpredictable water temperature changes commonly encountered in their natural environment.
