During gradual air exposure, Amia calva show no reduction in oxygen consumption, no increase in plasma urea levels or in urea excretion. Blood pH remains constant, and plasma total CO2, PCO2, HCO3-. total ammonia and NH3 concentrations all rise significantly. Exposure to 923 μmol/l NH4Cl does not elicit an increase in urea production or airbreathing. Aquatic hypoxia without access to air does not cause a reduction in aerobic metabolism, and moderate levels result in death. These results suggest that Amia are incapable of aestivation, due to an inability to detoxify ammonia to urea and reduce metabolism, and die following three to five days of air exposure.
KeywordsAmia calva aestivation ammonia urea hypoxia
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