Behavioral thermoregulation and critical thermal limits of giant keyhole limpet Megathura crenulata(Sowerby 1825) (Mollusca; Vetigastropoda)

• We obtained a preferred temperature for M. crenulata of 18.6±1.2 °C.
• Displacement velocity of limpets diminished from 46.0 to 17.9 cm h−1 once the organisms located the preferred temperature.
• The CTMax, at 50% was 27.2, 27.9 and 28.3 °C for organisms acclimated at different temperatures.

The thermoregulatory behavior of the giant keyhole limpet Megathura crenulata was determined in a horizontal thermal gradient during the day at 18.9 °C and 18.3 °C for the night. The final preferendum determined for giant keyhole limpets was of 18.6±1.2 °C.Limpets' displacement velocity was 10.0±3.9 cm h−1 during the light phase and 8.4±1.6 cm h−1 during the dark phase. The thermotolerance (measured as CTMax at 50%) was determined in a keyhole limpet in three acclimation temperatures 17, 20, and 23 °C. Limpets were subjected to water increasing temperatures at a rate of 1 °C every 30 min, until they detached from the substrate. The critical thermal maximum at 50% was 27.2, 27.9 and 28.3 °C respectively.