Validation of CTmaxprotocols using cased and uncased Pycnopsyche guttifer (Trichoptera: Limnephilidae) larvae

Abstract

The critical thermal maximum (CTmax) of a northern Lower Michigan population of Pycnopsyche guttifer was determined using four rates of temperature increase (0.10, 0.33, 0.50, and 0.70ºC per minute), and two case states (intact and removed). Across all temperature increase rates, larvae removed from their cases had a significantly lower mean CTmax than those remaining in their cases, suggesting that the case can increase the larva’s ability to tolerate thermal stress, possibly due to respiratory advantages. Regardless of case state, mean CTmax was significantly lower at the 0.10ºC per minute increase rate than the other three rates, likely due to increased exposure time. Our results indicate that CTmax studies done using 0.33-0.70ºC per minute increase protocols would be comparable with each other, but not with studies using an increase rate of 0.10ºC per minute.