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

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.

Beyond thermal limits: comprehensive metrics of performance identify key axes of thermal adaptation in ants

“…While CT max is a useful metric for predicting how species will respond to temperature increases, survival is influenced both by the intensity and the duration of thermal stress (Rezende, Castañeda & Santos ). Our results and those of others (Magozzi & Calosi ; McDonnell & Chapman ) suggest that moderate increases in temperature can negatively impact performance, especially when individuals are exposed to chronic increases in temperature. Caution is therefore warranted when using CT max alone to predict the vulnerability of species to climate warming.…”

Limited variability in upper thermal tolerance among pure and hybrid populations of a cold-water fish

“…Although some studies have found similar evidence for intraspecific variation in upper thermal tolerance in salmonids (Eliason et al ., 2011; Gradil, 2015), including brook trout (McDermid et al ., 2012; Stitt et al ., 2014), others have found no differences between populations (Elliott and Klemetsen, 2002), differences between hybrid and pure crosses (Fields et al ., 1987), evidence for heterosis in thermal tolerance of copepods (Willett, 2012) and evidence for increased survival of heterozygotes at near-lethal temperatures in Eastern mosquitofish ( Gambusia holbrooki ; Meffe et al ., 1995). To our knowledge, agitation temperature has been assessed in fishes only once before (McDonnell and Chapman, 2015) but was studied in relationship to sex and acclimation temperature.…”

“…Rock substrate was provided in each chamber to act as potential fish refuge. During the trial, individuals were subjected to a constant (0.3°C/min) increase in water temperature that was controlled, monitored and recorded by a temperature-control unit and software (TMP-REG, AutoResp; Loligo Systems; McDonnell and Chapman, 2015). Agitation temperatures were recorded for each fish as the point where an obvious shift in behaviour first occurred.…”

“…As acclimation temperature ( T a ) has been found to be correlated positively with CT max (Cox et al ., 1974; Zhang and Kieffer, 2014; McDonnell and Chapman, 2015, although see Galbreath et al ., 2004; Recsetar et al ., 2012), the ancestral history and origin of a population are thought to be linked to an organism's ability to tolerate temperature increases (Stockwell et al ., 2003; McDermid et al ., 2012) and, as such, stream temperature regimes may result in population-specific thermal tolerance. A relatively new metric to assess thermal tolerance, agitation temperature, described by McDonnell and Chapman (2015) as the temperature at which a fish first begins to exhibit refugia-seeking behaviour (circling of the chamber, seeking refuge in substrate), may also provide insight to how quickly individuals can sense and attempt to react to environmental change. In addition, the difference between these two traits (CT max –agitation window) may represent a fitness metric yet unexplored in thermal tolerance literature.…”

Tropical fish in a warming world: thermal tolerance of Nile perchLates niloticus(L.) in Lake Nabugabo, Uganda

“…Fish were placed in their respirometry chamber and acclimated to the system for 2 h before initiating the trial, consistent with previous respirometry experiments conducted at the Nabugabo field station (Schofield and Chapman, 2000; Reardon et al ., 2011; McDonnell and Chapman, 2015). During this time, the length of the measurement period was determined by observing how rapidly oxygen was declining in the chamber.…”