Thermal tolerance and preference of the freshwater shrimp Palaemonetes kadiakensis

Abstract

1. 1.|Freshwater shrimp, acclimated to a fluctuating room temperature regime (20–28°C) and five different constant temperatures (24, 26, 28, 30 and 32°C), were tested to characterize their upper tolerance limits and to assess their abilities to thermoregulate behaviourally within a horizontal thermal gradient. 2. 2.|Specimens tested to determine the upper temperature survival limits manifested five distinct responses to thermal stress: initial disorientation, complete disorientation, onset of tail fold, end of tail fold and total loss of movement. 3. 3.|The upper temperature survival limit for each group (expressed as the critical thermal maximum temperature —CTM) ranged from 37 to 40°C. CTM values were found to vary directly with the acclimation temperature. 4. 4.|Specimens tested in a horizontal gradient (18—36°C) selected temperatures ranging from 28 to 32°C. Preferred tempertures did not vary according to acclimation. .