At the edge of the thermal window: effects of elevated temperature on the resting metabolism, hypoxia tolerance and upper critical thermal limit of a widespread African cichlid. (7th December 2015)

• Record Type: Journal Article
• Authors: McDonnell, Laura H.; Chapman, Lauren J.
• Is Part Of: Conservation physiology. Volume 3:Number 1(2015:Jun.)
• Publication Date: 2015-12-07
• Subjects: Critical oxygen tension -- fish physiology -- respirometry -- thermal stress -- thermal tolerance -- tropical fish; Nature -- Effect of human beings on -- Periodicals; Conservation biology -- Periodicals; 577.05
• DOI: 10.1093/conphys/cov050
• Languages: English
• ISSNs: 2051-1434

Abstract

Abstract : Small annual temperature fluctuations may limit the plastic responses of tropical fish to thermal stress. We measured the acclimation capacity of an African cichlid to elevated water temperatures by quantifying resting metabolic rate and both thermal and low-oxygen tolerance after short-term exposure to temperatures within and above its natural range. Abstract : Tropical inland fishes are predicted to be especially vulnerable to thermal stress because they experience small temperature fluctuations that may select for narrow thermal windows. In this study, we measured resting metabolic rate (RMR), critical oxygen tension ( P crit ) and critical thermal maximum (CTMax ) of the widespread African cichlid ( Pseudocrenilabrus multicolor victoriae ) in response to short-term acclimation to temperatures within and above their natural thermal range. Pseudocrenilabrus multicolor collected in Lake Kayanja, Uganda, a population living near the upper thermal range of the species, were acclimated to 23, 26, 29 and 32°C for 3 days directly after capture, and RMR and P crit were then quantified. In a second group of P. multicolor from the same population, CTMax and the thermal onset of agitation were determined for fish acclimated to 26, 29 and 32°C for 7 days. Both RMR and P crit were significantly higher in fish acclimated to 32°C, indicating decreased tolerance to hypoxia and increased metabolic requirements at temperatures only slightly (∼1°C) above their natural thermal range. The CTMax increased with acclimation temperature, indicating some degree of thermal compensation induced by short-term exposure to higher temperatures. However, agitation temperature (likely to represent an avoidance response to increased temperature during CTMax trials) showed no increase with acclimation temperature. Overall, the results of this study demonstrate that P. multicolor is able to maintain its RMR and P crit across the range of temperatures characteristic of its natural habitat, but incurs a higher cost of resting metabolism and reduced hypoxia tolerance at temperatures slightly above its present range.