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Continuous measurement of oxygen tensions in the air-breathing organ of Pacific tarpon (Megalops cyprinoides) in relation to aquatic hypoxia and exercise
journal contribution
posted on 2023-05-18, 13:26 authored by Seymour, RS, Farrell, AP, Christian, K, Clark, TD, Bennett, MB, Wells, RMG, Baldwin, JThe Pacific tarpon is an elopomorph teleost fish with an air-breathing organ (ABO) derived from a physostomous gas bladder. Oxygen partial pressure (PO2) in the ABO was measured on juveniles (238 g) with fiber-optic sensors during exposure to selected aquatic PO2 and swimming speeds. At slow speed (0.65 BL s−1), progressive aquatic hypoxia triggered the first breath at a mean PO2 of 8.3 kPa. Below this, opercular movements declined sharply and visibly ceased in most fish below 6 kPa. At aquatic PO2 of 6.1 kPa and swimming slowly, mean air-breathing frequency was 0.73 min−1, ABO PO2 was 10.9 kPa, breath volume was 23.8 ml kg−1, rate of oxygen uptake from the ABO was 1.19 ml kg−1 min−1, and oxygen uptake per breath was 2.32 ml kg−1. At the fastest experimental speed (2.4 BL s−1) at 6.1 kPa, ABO oxygen uptake increased to about 1.90 ml kg−1 min−1, through a variable combination of breathing frequency and oxygen uptake per breath. In normoxic water, tarpon rarely breathed air and apparently closed down ABO perfusion, indicated by a drop in ABO oxygen uptake rate to about 1% of that in hypoxic water. This occurred at a wide range of ABO PO2 (1.7–26.4 kPa), suggesting that oxygen level in the ABO was not regulated by intrinsic receptors.
History
Publication title
Journal of Comparative Physiology. BVolume
177Issue
5Pagination
579-587ISSN
0174-1578Department/School
Institute for Marine and Antarctic StudiesPublisher
Springer-VerlagPlace of publication
175 Fifth Ave, New York, USA, Ny, 10010Repository Status
- Restricted