Ecologically‐relevant Temperatures and Stress in Desert Pupfish

Abstract

The Southwest United States was much wetter in its recent past. For instance, Death Valley was inundated with the 100m deep Lake Manley just 10,000 years ago. As the waters receded, pupfish were isolated to the warm springs and spring outflows that characterize their current habitats. These fish spent much of their recent evolutionary history in cooler waters and now reside in waters that may be > 33 °C. We asked if rearing or acclimating fish at the ecologically relevant temperature of 33 °C would result in stress as compared to when fish are reared at 28 °C. Heat shock protein 90 was increased 4 fold during both a 4 h acute exposure as well as >3 week chronic exposure to 33 °C. Similarly, hypoxia‐induced factor alpha was increased ~3X at 33 °C. However, cortisol was reduced 2‐fold in 33 °C chronically acclimated fish but not in acute exposure as compared to 28 °C acclimated controls. The Cdk inhibitory protein, p21 was increased during acute exposure but not during chronic exposure to 33 °C. Taken together, these data suggest that stress may be differentially managed and processed in context. For instance, while it may be possible for p21 to repress cell cycle for 4 h, it is less likely that cell cycle may be inhibited for 3 weeks even in the face of environmental insult.