Accumulation of Uric Acid in the Land Crab,Cardisoma guanhumi

Variable amounts of white particulate matter occur in the hemocoel of the land crab, Cardisoma guanhumi. This material, mainly uric acid, accounts for 0.2–15.9% of the total dry weight of a series of crabs. The material appears to increase during intermolt. Concentrations of uric acid in the blood varied from 0.2 to 13.2 mg/100 ml. Urine and feces contained little or no uric acid. Estimates of NH3-N (3.9 mg/100 ml) in the blood of C. guanhumi are higher, and those of non-protein N (10.2 mg/100 ml) are lower, than corresponding values reported for other decapods. The crab's rate of nitrogen release (0.4 mg/10 g/day) into water is similar to that reported for other terrestrial crustaceans. About one-third of this is released as NH3. The urine of C. guanhumi is frequently nearly free of nitrogen, and its stomach fluid contains about five to seven times as much as does its blood. Implications of these findings in the crab's metabolism and excretion are discussed.