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Journal of Experimental Biology, Vol 203, Issue 24 3785-3793, Copyright © 2000 by Company of Biologists

JOURNAL ARTICLES

The effect of graded hypoxia on the metabolic rate and buccal activity of a lungless salamander (Desmognathus fuscus)

EA Sheafor, SC Wood and GJ Tattersall
Kent State University, Biology Department, PO Box 5190, Kent, OH 44242, USA. bsheafor@kent.edu

The hypothesis that the lungless salamander Desmognathus fuscus responds actively to hypoxia was tested. Patterns of buccal movements [apneic period duration, the duration (min h(-)(1)) of buccal pumping and buccal pumping frequency], heart rate and metabolic rate (rates of oxygen uptake and carbon dioxide output) were determined during a control period (21 % oxygen), a hypoxic period (2, 5, 6.5, 8 or 10 % oxygen) and a recovery period (21 % oxygen). Hypoxic salamanders maintained their rate of oxygen uptake at control levels until a critical oxygen level between 10 and 8 % oxygen was reached. The rate of carbon dioxide output remained constant across all oxygen levels, except for a significant increase during exposure to 5 % oxygen. The buccal activity of lungless salamanders was responsive to environmental hypoxia, with a significant stimulation during exposure to 6.5 % and 5 % oxygen. Buccal pumping frequency was inhibited at 2 % oxygen. Heart rate was stimulated at all hypoxic levels except 2 % O(2). During recovery, metabolic rate and heart rate returned to control levels within 20 min after all hypoxic exposures. The durations of apneic periods increased significantly compared with the hypoxic value during recovery from exposure to 10 %, 6.5 % and 5 % oxygen. Overall, the animals responded actively to hypoxia by increasing the duration of buccal activity as oxygen levels decreased. The ability of these changes to facilitate oxygen uptake is not known. However, the response of the dusky salamander to low levels of oxygen is analogous to the hypoxic ventilatory response observed in lunged vertebrates.


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T. McKean, G. Li, and K. Wei
Cardiac effects of hypoxia in the neotenous tiger salamander Ambystoma tigrinum
J. Exp. Biol., June 15, 2002; 205(12): 1725 - 1734.
[Abstract] [Full Text] [PDF]


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