title: Increased temperature tolerance of the air-breathing Asian swamp eel Monopterus albus after high-temperature acclimation is not explained by improved cardiorespiratory performance.
abstract: This study investigated the hypothesis that in the Asian swamp eel Monopterus albus, an air-breathing fish from south-east Asia that uses the buccopharyngeal cavity for oxygen uptake, the upper critical temperature (TU) is increased by acclimation to higher temperature, and that the increased TU is associated with improved cardiovascular and respiratory function. Monopterus albus were therefore acclimated to 27° C (current average) and 32° C (current maximum temperature as well as projected average within 100-200 years), and both the effect of acclimation and acute temperature increments on cardiovascular and respiratory functions were investigated. Two weeks of heat acclimation increased upper tolerated temperature (TU ) by 2° C from 36·9 ± 0·1° C to 38·9 ± 0·1° C (mean ± s.e.). Oxygen uptake (M˙O2) increased with acclimation temperature, accommodated by increases in both aerial and aquatic respiration. Overall, M˙O2 from air (M˙O2a ) was predominant, representing 85% in 27° C acclimated fish and 80% in 32° C acclimated fish. M˙O2 increased with acute increments in temperature and this increase was entirely accommodated by an increase in air-breathing frequency and M˙O2a . Monopterus albus failed to upregulate stroke volume; rather, cardiac output was maintained through increased heart rate with rising temperature. Overall, acclimation of M. albus to 32° C did not improve its cardiovascular and respiratory performance at higher temperatures, and cardiovascular adaptations, therefore, do not appear to contribute to the observed increase in TU.
authors.affiliation: Zoophysiology, Aarhus University, Department of Bioscience, C. F. Møllers Allé 3, 8000 Aarhus C, Denmark.|College of Aquaculture and Fisheries, Can Tho University, Campus II, 3/2 Street, Nink Kieu District, Can Tho City, Vietnam.
authors.forename: S
authors.initials: S
authors.lastname: Lefevre
authors.affiliation: Zoophysiology, Aarhus University, Department of Bioscience, C. F. Møllers Allé 3, 8000 Aarhus C, Denmark.|College of Aquaculture and Fisheries, Can Tho University, Campus II, 3/2 Street, Nink Kieu District, Can Tho City, Vietnam.
authors.forename: I
authors.initials: I
authors.lastname: Findorf
authors.affiliation: Zoophysiology, Aarhus University, Department of Bioscience, C. F. Møllers Allé 3, 8000 Aarhus C, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Bayley
authors.affiliation: College of Aquaculture and Fisheries, Can Tho University, Campus II, 3/2 Street, Nink Kieu District, Can Tho City, Vietnam.
authors.forename: D T T
authors.initials: DT
authors.lastname: Huong
authors.affiliation: Zoophysiology, Aarhus University, Department of Bioscience, C. F. Møllers Allé 3, 8000 Aarhus C, Denmark.
authors.forename: T
authors.initials: T
authors.lastname: Wang
mesh_terms: D000064:Acclimatization; D000818:Animals; D005260:Female; D010101:Oxygen Consumption; D012143:Respiratory Physiological Phenomena; D023701:Smegmamorpha / Q000502:physiology*; D013696:Temperature
keywords: blood flow; blood pressure; climate change; heart rate; respiratory partitioning; respirometry