EFFECTS OF TEMPERATURE AND WATER-LOSS ON TERRESTRIAL LOCOMOTOR PERFORMANCE IN LAND CRABS - INTEGRATING LABORATORY AND FIELD STUDIES

Terrestrial and semi-terrestrial crustaceans are exposed to fluctuatio ns in ambient temperature and conditions that favor evaporative water loss. These environmental stresses alter performance limits in the lab oratory and behavior in the field. The maximal rate of oxygen consumpt ion, maximum aerobic speed, and endurance capacity are greater at a bo dy temperature (T-b) of 24 degrees C than at 15 degrees C or 30 degree s C in the ghost crab, Ocypode quadrata. The total metabolic cost to m ove at the same relative speed is greater at a T-b of 24 degrees C tha n at 15 degrees C. Slower aerobic kinetics at 15 degrees C result in a smaller relative contribution of oxidative metabolism to total metabo lic cost. However, the relative contributions from accelerated glycoly sis are similar at both temperatures. When locomotion is intermittent, the total distance traveled before fatigue can be similar at T(b)s of 15 and 24 degrees C but result from different movement and pause dura tions at these temperatures. Performance limits of the ghost crab are negatively affected by dehydration and are sensitive to rates of water loss. In the laboratory, endurance capacity of the fiddler crab, Uca pugilator, is greater at a T-b of 30 degrees C than at 25 degrees C. I n the field, freely moving fiddler crabs with a T-b of 30 degrees C tr avel at faster mean preferred speeds, as determined by motion analysis , than crabs at 25 degrees C. Data for Land crabs support and advance general ectothermic models for the effects of temperature and dehydrat ion on locomotor performance.