Oxygen uptake (MO2) was measured in the terrestrial crabs Ocypode quadrata (Fabricius, 1787), Goniopsis cruentata (Latreille, 1803) and Cardisoma guanhumi Latreille, 1825 as a function of digestive state to determine the magnitude and time course of specific dynamic action (SDA). Following 5 days of feeding ad libitum on fish flesh, ''steady-state'' MO2 was about 2.8, 1.0 and 1.6 mum.g-1.h-1 in Ocypode (29-31-degrees-C), Goniopsis (23-25-degrees-C) and Cardisoma (29-31-degrees-C), respectively. After 5 days of fasting, ''steady-state'' MO2 was decreased greatly to 1.0 and 0.5 mum.g-1.h-1 in Ocypode and Cardisoma, respectively, but was not significantly changed from feeding values in Goniopsis. Time-course experiments indicated that the peak in MO2 following a single large meal occurred within 8 h in both Ocypode and Cardisoma. The apparent SDA persisted for longer than 50 h in Cardisoma, but less than 42 h in Ocypode. These data show that an apparent SDA of large magnitude and variable time course can occur in land crabs. However, the absence of any apparent SDA effect in Goniopsis indicates that it is not a necessary accompaniment to feeding in all terrestrial brachyurans, and must be verified on a species-by-species basis.
