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Journal of Experimental Biology 49,437-452 (1968)
Published by Company of Biologists 1968

Respiration in the African Lungfish Protopterus Aethiopicus : I. Respiratory Properties of Blood and Normal Patterns of Breathing and Gas Exchange

CLAUDE LENFANT ¹ and KJELL JOHANSEN ¹

¹ Institute of Respiratory Physiology--Firland Sanatorium and Departments of Medicine, Physiology and Zoology, University of Washington, Seattle, Washington, 98105, U.S.A.

1. Respiratory properties of blood and pattern of aerial and aquatic breathing and gas exchange have been studied in the African lungfish, Protopterus aethiopicus.

2. The mean value for haematocrit was 25%. Haemoglobin concentration was 6.2 g% and O₂ capacity 6.8 vol. %.

3. The affinity of haemoglobin for O₂ was high. P₅₀ was 10 mm. Hg at P_COCO2, 6 mm. Hg and 25 °C. The Bohr effect was smaller than for the Australian lungfish, Neoceratodus, but exceeded that for the South American lungfish, Lepidosiren. The O₂ affinity showed a larger temperature shift in Protopterus than Neoceratodus.

4. The CO₂ combining power and the over-all buffering capacity of the blood exceeded values for the other lungfishes.

5. Both aerial and aquatic breathing showed a labile frequency. Air exposure elicited a marked increase in the rate of air breathing.

6. When resting in aerated water, air breathing accounted for about 90% of the O₂ absorption. Aquatic gas exchange with gills and skin was 2.5 times more effective than pulmonary gas exchange in removing CO₂. The low gas-exchange ratio for the lung diminished further in the interval between breaths.

7. Protopterus showed respiratory independence and a maintained O₂ uptake until the ambient O₂ and CO₂ tensions were 85 and 35 mm. Hg respectively. A further reduction in O₂ tension caused an abrupt fall in the oxygen uptake.

8. Gas analysis of blood samples drawn from unanaesthetized, free-swimming fishes attested to the important role of the lung in gas exchange and the high degree of functional separation in the circulation of oxygenated and deoxygenated blood.

Note:

This work was supported by grant GB 4038 from the National Science Foundation and grant HE-08405 from the National Institute of Health.

Established Investigator, American Heart Association. Work supported by Northeastern Chapter, Washington State Heart Association.

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