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Changes in cardiac output during swimming and aquatic hypoxia in the air-breathing Pacific tarpon
journal contribution
posted on 2023-05-18, 13:25 authored by Clark, TD, Seymour, RS, Christian, K, Wells, RMG, Baldwin, J, Farrell, APPacific tarpon (Megalops cyprinoides) use a modified gas bladder as an air-breathing organ (ABO). We examined changes in cardiac output (V̇b) associated with increases in air-breathing that accompany exercise and aquatic hypoxia. Juvenile (0.49 kg) and adult (1.21 kg) tarpon were allowed to recover in a swim flume at 27 °C after being instrumented with a Doppler flow probe around the ventral aorta to monitor V̇b and with a fibre-optic oxygen sensor in the ABO to monitor air-breathing frequency. Under normoxic conditions and in both juveniles and adults, routine air-breathing frequency was 0.03 breaths min− 1 and V̇b was about 15 mL min− 1 kg− 1. Normoxic exercise (swimming at about 1.1 body lengths s− 1) increased air-breathing frequency by 8-fold in both groups (reaching 0.23 breaths min− 1) and increased V̇b by 3-fold for juveniles and 2-fold for adults. Hypoxic exposure (2 kPa O2) at rest increased air-breathing frequency 19-fold (to around 0.53 breaths min− 1) in both groups, and while V̇b again increased 3-fold in resting juvenile fish, V̇b was unchanged in resting adult fish. Exercise in hypoxia increased air-breathing frequency 35-fold (to 0.95 breaths min− 1) in comparison with resting normoxic fish. While juvenile fish increased V̇b nearly 2-fold with exercise in hypoxia, adult fish maintained the same V̇b irrespective of exercise state and became agitated in comparison. These results imply that air-breathing during exercise and hypoxia can benefit oxygen delivery, but to differing degrees in juvenile and adult tarpon. We discuss this difference in the context of myocardial oxygen supply.
History
Publication title
Comparative Biochemistry and Physiology. Part AVolume
148Pagination
562-571ISSN
1095-6433Department/School
Institute for Marine and Antarctic StudiesPublisher
Elsevier Science IncPlace of publication
360 Park Ave South, New York, USA, Ny, 10010-1710Repository Status
- Restricted