title: Some like it hot: Thermal tolerance and oxygen supply capacity in two eurythermal crustaceans.
abstract: Thermal sensitivity of the cardiorespiratory oxygen supply capacity has been proposed as the cardinal link underlying the upper boundary of the temperature niche in aquatic ectotherms. Here we examined the evidence for this link in two eurythermal decapods, the Giant tiger shrimp (Penaeus monodon) and the European crayfish (Astacus astacus). We found that both species have a temperature resistant cardiorespiratory system, capable of maintaining oxygen delivery up to their upper critical temperature (Tcrit). In neither species was Tcrit reduced in hypoxia (60% air saturation) and both species showed an exponential increase in heart and gill ventilation rates up to their Tcrit. Further, failure of action potential conduction in preparations of A. astacus motor neurons coincided with Tcrit, indicating that compromised nervous function may provide the underlying determinant for Tcrit rather than oxygen delivery. At high temperatures, absolute aerobic scope was maintained in P. monodon, but reduced in A. astacus. However, A. astacus also displayed reduced exercise intensity indicating that impaired muscle performance with resulting reduced tissue oxygen demand may explain the reduced scope rather than insufficient oxygen supply capacity. This interpretation agrees with early literature on aquatic ectotherms, correlating loss of nervous function with impaired locomotion as temperatures approach Tcrit.
authors.affiliation: 1] Department of Bioscience, Aarhus University, Aarhus, Denmark [2] College of Aquaculture and Fisheries, Can Tho University, Can Tho, Vietnam.
authors.forename: Rasmus
authors.initials: R
authors.lastname: Ern
authors.affiliation: College of Aquaculture and Fisheries, Can Tho University, Can Tho, Vietnam.
authors.forename: Do Thi Thanh
authors.initials: do TT
authors.lastname: Huong
authors.affiliation: College of Aquaculture and Fisheries, Can Tho University, Can Tho, Vietnam.
authors.forename: Nguyen Thanh
authors.initials: NT
authors.lastname: Phuong
authors.affiliation: Department of Bioscience, Aarhus University, Aarhus, Denmark.
authors.forename: Peter Teglberg
authors.initials: PT
authors.lastname: Madsen
authors.affiliation: Department of Bioscience, Aarhus University, Aarhus, Denmark.
authors.forename: Tobias
authors.initials: T
authors.lastname: Wang
authors.affiliation: Department of Bioscience, Aarhus University, Aarhus, Denmark.
authors.forename: Mark
authors.initials: M
authors.lastname: Bayley
mesh_terms: D000200:Action Potentials; D000222:Adaptation, Physiological; D000818:Animals; D003445:Crustacea / Q000502:physiology*; D005880:Gills / Q000502:physiology; D006339:Heart Rate; D006358:Hot Temperature; D000860:Hypoxia; D009046:Motor Neurons / Q000502:physiology; D010101:Oxygen Consumption