Aerial Versus Aquatic Oxygen Consumption in Larvae of the Clawed Frog, Xenopus Laevis

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Abstract
Tadpoles of Xenopus laevis Daudin can extract oxygen from both air and water. When these larvae have access to air, aerial oxygen uptake averages 16.6% of total oxygen consumption in normoxic water, and increases to 100% of net oxygen consumption in hypoxic water. Neither anaerobiosis nor increased buccopharyngeal ventilation occur in response to hypoxia. If tadpoles are prevented from surfacing to breathe air, they can maintain normal oxygen consumption through aquatic respiration alone in normoxic water, but not in hypoxic water. Unlike air-breathing larvae, exclusively water-breathing larvae respond to aquatic hypoxia by increasing their buccal pumping rate and by accumulating lactate. Even though Xenopus larvae can survive without air for many days, aerial respiration is necessary for other functions: tolerance of hypoxia, normal feeding, locomotion and buoyancy regulation.