Interaction of Respiration, Ion Regulation, and Acid-Base Balance in the Everyday Life of Aquatic Crustaceans |
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Authors: | HENRY RAYMOND P; WHEATLY MlCHELE G |
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Institution: | Department of Zoology and Wildlife Science, Auburn University Auburn, Alabama 36849-5414
Department of Zoology, University of Florida Gainesville, Florida 32611 |
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Abstract: | Extracellular and intracellular acid-base balance is necessaryfor the maintenance of normal metabolic processes. The primarysource of acid is metabolically produced CO2, and the CO2/HCO3system is the most significant buffer. The regulation of acid-basebalance is complex, involving the interaction between respiratorygas exchange and ion transport. In aquatic crustaceans respirationis governed by the need to extract oxygen from water, an O2-poormedium; thus, acid-base balance is maintained primarily throughion transport mechanisms. These mechanisms include Na+/H+ andCl/HCO3 exchange processes that are sensitiveto the extracellular acid-base status of the animal. In marinecrabs, ion regulation and acid-base balance are accomplishedby the posterior gills, while in freshwater species all gillsand the antennal gland perform these functions. Intracellularacid-base balance appears to be maintained primarily by iontransport across the cell membrane. Hemolymph pH varies inverselywith acclimation temperature and salinity. In both cases Pco2remains nearly constant, and the pH change is a result of changesin hemolymph HCO3 concentrations brought about by ionexchange mechanisms. Environmental hypercapnia or hyperoxiainduces a repiratory acidosis characterized by increased Pco2,low pH, and elevated HCO3; this is partially compensatedfor by ion exchange processes that bring about a further increasein hemolymph HCO3. Exercise causes a mixed respiratoryand metabolic acidosis with compensation via H+ ion excretionand hyperventilation. |
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