Behavioral Thermoregulation in Hemigrapsus nudus, the Amphibious Purple Shore Crab

• Published in: The Biological bulletin (Lancaster) 2003-02, Vol.204 (1), p.38-49
• Main Author: McGaw, I. J.
• Format: Article
• Language: English
• Subjects: Acclimatization; Analysis; Animal behavior; Animals; Behavior; Behavior, Animal; Biological research; Biology, Experimental; Body temperature; Body Temperature Regulation; Cooling; Crabs; Crustacea - physiology; Crustaceans; Emigration; Environmental aspects; Female; Hemigrapsus nudus; Male; Marine; Marine biology; Neurobiology and Behavior; Oxygen; Physiological aspects; Regulation; Sea water; Temperature; Water pollution; Water temperature
• ISSN: 0006-3185; 1939-8697
• DOI: 10.2307/1543494

The thermoregulatory behavior of Hemigrapsus nudus, the amphibious purple shore crab, was examined in both aquatic and aerial environments. Crabs warmed and cooled more rapidly in water than in air. Acclimation in water of 16 °C (summer temperatures) raised the critical thermal maximum temperature (CTMax); acclimation in water of 10 °C (winter temperatures) lowered the critical thermal minimum temperature (CTMin). The changes occurred in both water and air. However, these survival regimes did not reflect the thermal preferences of the animals. In water, the thermal preference of crabs acclimated to 16 °C was 14.6 °C, and they avoided water warmer than 25.5 °C. These values were significantly lower than those of the crabs acclimated to 10 °C; these animals demonstrated temperature preferences for water that was 17 °C, and they avoided water that was warmer than 26.9 °C. This temperature preference was also exhibited in air, where 10 °C acclimated crabs exited from under rocks at a temperature that was 3.2 °C higher than that at which the 16 °C acclimated animals responded. This behavioral pattern was possibly due to a decreased thermal tolerance of 16 °C acclimated crabs, related with the molting process. H. nudus was better able to survive prolonged exposure to cold temperatures than to warm temperatures, and there was a trend towards lower exit temperatures with the lower acclimation (10 °C) temperature. Using a complex series of behaviors, the crabs were able to precisely control body temperature independent of the medium, by shuttling between air and water. The time spent in either air or water was influenced more strongly by the temperature than by the medium. In the field, this species may experience ranges in temperatures of up to 20 °C; however, it is able to utilize thermal microhabitats underneath rocks to maintain its body temperature within fairly narrow limits.