Acid-base changes on transfer between sea- and freshwater in the Chinese crab, Eriocheir sinensis.
The time course of changes in hemolymph pH, PCO2 and bicarbonate concentration were followed in euryhaline Chinese crabs, Eriocheir sinensis, after transfer from seawater (SW) to freshwater (FW) and vice versa. In order to correlate these changes with the animal's ionic status, hemolymph osmolarity and Na+ and Cl- concentrations as well as net exchanges of acid-base equivalents with the external water were also measured. Transfer from SW to FW induced a metabolic alkalosis which peaked after 3 days and declined thereafter but remained significant by 29 days. Hemolymph PCO2 was markedly elevated in FW, thus moderating the increase in hemolymph pH. Osmolarity and Na+ and Cl- concentrations reached a new steady state at lowered values by 24-48 h and a significant outflux of acidic equivalents was measured only during the first 2 days. Transfer from FW to SW conversely induced a metabolic acidosis which was almost fully compensated by a marked hypocapnia. It is concluded that external acid-base exchanges coupled to ionic readjustments following a salinity transition cannot solely explain the associated acid-base disturbances, the metabolic component of which must also rely on tissular processes probably linked to cell volume regulation.
Truchot
J P
JP
Laboratoire de Neurobiologie et Physiologie Comparées, Université de Bordeaux I, URA CNRS 1126, Arcachon, France.
D000136:Acid-Base Equilibrium / Q000502:physiology*; D000641:Ammonia / Q000652:urine; D000818:Animals; D003386:Brachyura / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism; D005618:Fresh Water; D006458:Hemolymph / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D008297:Male; D009994:Osmolar Concentration; D010313:Partial Pressure; D012623:Seawater
D002245:Carbon Dioxide; D000641:Ammonia