Impacts of projected precipitation decline on water balance in the black land crab, (Gecarcinus ruricola) in The Bahamas

The black land crab, Gecarcinus ruricola, is a common inhabitant in Bahamian coastal forests, and is the most terrestrial of the Caribbean land crabs. Future climate changes predict a decrease in overall rainfall for the Caribbean region. We investigated the effects of water deprivation and mechanisms of water balance in G. ruricola. When deprived of water for 10 d the crabs lost >12 % of their body water, resulting in a concomitant increase in hemolymph osmolality. G. ruricola was able to maintain hemolymph osmolality by drinking water, as well as capillary uptake from non-saturated soils. However, generation of metabolic water did not appear to contribute to the water budget. Behavioral experiments showed that G. ruricola was primarily active during the hours of darkness. The dehydration status of the individual influenced activity levels, with crabs exhibiting increased activity after moderate (4 d) dehydration, but reducing activity following severe (8 d) dehydration. In experiments where food and water were offered to crabs, there was no clear effect of dehydration time to access either of these resources, although crabs took less time to detect the water source. In the field, G. ruricola were primarily observed following rainfall events: by reducing surface activity during dry periods, they were able to maintain a relatively constant hemolymph concentration, irrespective of local environmental conditions. While G. ruricola will likely survive any future climatic drying scenarios, it might not be without cost: they are less likely to be foraging above ground and this may hamper growth and reproductive capacity.