The effects of breathing different levels of O2 and CO2 on the diving responses of ducks (Anas platyrhynchos) and cormorants (Phalacrocorax auritus) |
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Authors: | Harry J Mangalam David R Jones |
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Institution: | (1) Department of Zoology, University of British Columbia, 6270 University Blvd, V6T 2A9 Vancouver, B.C., Canada |
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Abstract: | Summary The effects of breathing different levels of O2 and CO2 before forced dives were investigated in 5 dabbling ducks (White Pekin) and 5 deep divers (Double Crested Cormorants). Breathing
and heart rates, blood gases, and blood pH, were monitored. After breathing air before diving, ducks exhibited a slow decrease
in heart rate that reached a minimum of 20 beats·min−1 after 50 s submergence. The development of bradycardia was retarded if the duck breathed a hyperoxic gas mixture before diving
and was accelerated if the gas mixture was hypoxic and hypercapnic. The cormorants' diving heart rate decreased to a minimum
of about 60 beats·min−1 in less than 20 s and development of bradycardia was unaffected by different levels of O2 and CO2 breathed before diving. Consequently, bradycardia in forced dived cormorants was unrelated to changes in blood gases in the
dives which suggests that intravascular chemoreceptors are unimportant in initiating diving bradycardia in cormorants. |
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