Limited capacity for acclimation of thermal physiology in a salamander, Desmognathus brimleyorum

Abstract

Habitats vary in temperature both spatially and temporally. Variation in thermal habitat introduces challenges to organisms and may reduce fitness unless organisms can physiologically adjust to such changes. Theory predicts that thermal variability should influence the capacity for acclimation such that increased variation should favor a reduction in the thermal sensitivity of physiological traits. In this study, we investigated acclimation to constant and variable conditions in populations of the salamander Desmognathus brimleyorum from the Ouachita Mountains of Arkansas, USA. We exposed salamanders to constant and variable temperature regimes for 8 weeks in the laboratory. We then tested salamanders for acclimation of thermal tolerance, and the thermal sensitivities of swimming performance and standard metabolic rate. Our results indicate limited capacity for thermal acclimation to constant and variable conditions in D. brimleyorum. Instead, variation in physiological traits is dominated by differences among populations. Population differences do not appear to be correlated with observed variation in the thermal conditions of the streams, but are likely a consequence of structural and ecological differences. Due to the mixed support for theoretical predictions for acclimation to alternative environments, further consideration should be given to revising and expanding current theoretical models.

Relationship between Behavioral Thermoregulation and Physiological Function in Larval Stream Salamanders

“…We calculated Q 10 values over 58C increments across the entire thermal range tested to examine for differences in thermal sensitivity of metabolic rate. The Q 10 values indicate the factor by which a physiological process (e.g., metabolic rate) changes as a result of a 108C increase in temperature, with a value of 1.0 indicating that change is temperature independent (Dorcas et al, 2004;Homyack et al, 2010;Young and Gifford, 2013). For each 58C increment we report mean Q 10 values (61 SE).…”

“…Each trial was separated by at least 48 h, between which subjects were returned to their housing conditions. Preliminary testing and previous research indicated that lungless salamander metabolic rates stabilize after 3 h Young and Gifford, 2013). We chose to record VO 2 consumption over a 6-h session using the first 3 h to allow for metabolic stabilization and the last 3 h for data collection.…”

Thermal variation, thermal extremes and the physiological performance of individuals

“…In the first, swimming performance was determined as a function of temperature in salamanders. Both T opt,stat and maximal performance were normally distributed among individuals, with a greater than two-fold range evident in maximal performance (Young and Gifford, 2013). In the second, critical heart rate temperature (H crit , the temperature at which cardiac function declines) was determined in mussels collected from a range of intertidal sites along the West coast of North America and then maintained under common garden conditions for at least a month before measurement (Logan et al, 2012).…”

Allele specific expression and gene regulation explain transgressive thermal tolerance in non-native hybrids of the endangered California tiger salamander (Ambystoma californiense)

“…To assay CTMax, individuals were placed on a moist paper towel substrate in an opaque plastic container under a 100w ceramic infra-red heat emitting bulb (Zoo Med brand) (Layne & Claussen, 1982;Young & Gifford, 2013). Salamanders were constantly misted during the heating trials to avoid desiccation and were monitored for signs of behavioral abnormalities.…”

“…LRR was achieved when an individual was unable to right itself after 30 seconds on its back on a moist surface (W. I. Lutterschmidt & Hutchison, 1997;Young & Gifford, 2013). At this time temperature was recorded with an IR temperature gun 1cm from the dorsal and ventral surface of the body.…”