Osmotic and cationic urine concentrations/blood concentrations ratios in hyporegulating Ucides cordatus

Abstract

1. 1. In crabs exposed to sea-water for 96 hr, the haemolymph sodium, potassium, calcium, magnesium and osmotic concentrations have risen, but to levels below those found in the medium. 2. 2. Blood and urine were isosmotic for all exposure times. 3. 3. Urine sodium concentration was higher than that of blood during the first 24 hr. 4. 4. Urine, potassium and magnesium concentrations were higher than those of blood during every exposure period. 5. 5. Na U/B ratios and K U/B ratios significantly decreased, whereas Mg U/B ratios significantly increased along the sea-water exposure time. 6. 6. The role of the antennal gland is discussed.