Temperature insensitive O2 in blood of the tree frogChiromantis petersi |
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Authors: | Kjell Johansen Gunnar Lykkeboe Sonja Kornerup and G M O Maloiy |
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Institution: | (1) Department of Zoophysiology, University of Aarhus, DK-8000 Aarhus C., Denmark;(2) Comparative Animal Physiology Research Unit, University of Nairobi, P.O. Box 30197, Nairobi, Kenya |
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Abstract: | Summary Respiratory gas exchange and blood respiratory properties have been studied in the East-African tree frogChiromantis petersi. This frog is unusually xerophilous, occupies dry habitats and prefers body temperatures near 40°C and direct solar exposure. Total O2 uptake was low at 81 l O2·g–1·h–1±19.0 (SD) at 25°C increasing to 253.5 l O2·g–1·h–1±94.8 (SD) at 40°C giving aQ
10 value of 2.1. Skin O2 uptake at 25°C was 38.5% of total. The gas exchange ratio was 0.71 for whole body gas exchange, 0.61 for the lungs and 1.02 for the skin at 25°C.Blood O2 affinity was low with aP
50 of 47.5 mmHg at 25°C and pH 7.65. Then
H-value at 25°C increased from 2.7 aroundP
50 to 5.0 at O2 saturations exceeding 70–80%. Surprisingly, blood O2 affinity was nearly insensitive to temperature expressed by a H value of ±1.0 kcal·mole between 25 and 40°C.The adaptive significance of the low O2 affinity, the increase ofn
H with O2 saturation and the temperature insensitive O2-Hb binding is discussed in relation to the high and fluctuating body temperatures ofChiromantis. |
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