Anaemia only causes a small reduction in the upper critical temperature of sea bass: is oxygen delivery the limiting factor for tolerance of acute warming in fishes?
To address how the capacity for oxygen transport influences tolerance of acute warming in fishes, we investigated whether a reduction in haematocrit, by means of intra-peritoneal injection of the haemolytic agent phenylhydrazine, lowered the upper critical temperature of sea bass. A reduction in haematocrit from 42±2% to 20±3% (mean ± s.e.m.) caused a significant but minor reduction in upper critical temperature, from 35.8±0.1 to 35.1±0.2°C, with no correlation between individual values for haematocrit and upper thermal limit. Anaemia did not influence the rise in oxygen uptake between 25 and 33°C, because the anaemic fish were able to compensate for reduced blood oxygen carrying capacity with a significant increase in cardiac output. Therefore, in sea bass the upper critical temperature, at which they lost equilibrium, was not determined by an inability of the cardio-respiratory system to meet the thermal acceleration of metabolic demands.
UMR5119 ECOSYM, Place Eugène Bataillon, Université Montpellier 2, 34090 Montpellier, France. Zoophysiology, Department of Biological Sciences, University of Aarhus, 8000 Aarhus C, Denmark. tobias.wang@biology.au.dk.
Tobias
T
Wang
UMR5119 ECOSYM, Place Eugène Bataillon, Université Montpellier 2, 34090 Montpellier, France. Zoophysiology, Department of Biological Sciences, University of Aarhus, 8000 Aarhus C, Denmark.
Sjannie
S
Lefevre
UMR5119 ECOSYM, Place Eugène Bataillon, Université Montpellier 2, 34090 Montpellier, France. Zoophysiology, Department of Biological Sciences, University of Aarhus, 8000 Aarhus C, Denmark.
Nina K
NK
Iversen
UMR5119 ECOSYM, Place Eugène Bataillon, Université Montpellier 2, 34090 Montpellier, France. Zoophysiology, Department of Biological Sciences, University of Aarhus, 8000 Aarhus C, Denmark.
Inge
I
Findorf
UMR5119 ECOSYM, Place Eugène Bataillon, Université Montpellier 2, 34090 Montpellier, France. Zoophysiology, Department of Biological Sciences, University of Aarhus, 8000 Aarhus C, Denmark.
Rasmus
R
Buchanan
UMR5119 ECOSYM, Place Eugène Bataillon, Université Montpellier 2, 34090 Montpellier, France.
David J
DJ
McKenzie
D000064:Acclimatization / Q000502:physiology*; D000740:Anemia / Q000139:chemically induced; D000818:Animals; D001492:Bass / Q000378:metabolism / Q000502:physiology*; D002302:Cardiac Output; D006400:Hematocrit; D010101:Oxygen Consumption / Q000187:drug effects; D010659:Phenylhydrazines / Q000494:pharmacology; D013696:Temperature
D010659:Phenylhydrazines; C030299:phenylhydrazine
Cardiovascular; Fish; Haematocrit; Oxygen transport; Thermal tolerance