Thermal preference, tolerance and temperature-dependent respiration in the California sea hare <i>Aplysia californica</i>

Abstract

The thermoregulatory behavior of sea hare Aplysia californica was determined in a horizontal thermal gradient; with a preferred temperature (PT) of 18.3˚C for the day cycle and 20.8˚C for the night cycle. The displacement velocity demonstrated an initial rate of 30 cm•h −1 and gradually the velocity diminished to 18 cm•h −1 with several fluctuations mainly at 02:00 am. Critical Temperature Maxima (CTMax refers to the temperature point where at least 50% of the experimental group have a loss of attachment) was measured at three acclimation temperatures (16˚C, 19˚C and 22˚C). At the lowest acclimation temperature (16˚C), 50% of the experimental group had an attachment loss at CTMax 32.7˚C, and in a higher acclimation temperature (22˚C) CTMax was 36.2˚C. The Oxygen Consumption Rate (OCR) was closely correlated to acclimation temperature, and at 16˚C and 19˚C sea hare had a relatively stable metabolic rate, with OCR increasing to 9 mg O 2 h −1 •kg −1 w.w. in a higher acclimation temperature.