Meeting Abstract
Laboratory studies of organismal thermal biology often rely on acclimation to constant temperatures to assess physiological or performance responses, yet organisms in their natural environment are exposed temperature variation across spatial and temporal scales. Incorporating thermal variability into tests of organismal responses to temperature might help elucidate how organisms respond to temperature in variable environments. Additionally, metabolic responses under variable thermal conditions may be an important and often overlooked component influencing an organism’s fundamental thermal niche. The southern redbelly dace (Chrosomus erythrogaster) and the central stoneroller (Campostoma anomalum) are two species of functionally-similar minnows that display differences in their realized thermal niches along a stream-size gradient of temperature. To test how exposure to a variable thermal regime affects metabolic physiology, we measured the metabolic rates of dace and stonerollers acclimated to either constant (20°C) or variable (mean = 20°C; range = 17-23°C) temperature conditions. We then used intermittent-flow respirometry to compare standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic scope (AS) of dace and stonerollers at 15, 20, and 25°C. We also compared responses between dace and stonerollers to determine if temperature variation contributes to differences in the realized thermal niches of these species. We found that fish acclimated to a variable thermal regime maintained higher overall AS across the range of test temperatures when compared to fish acclimated to constant temperatures, except for the stonerollers at 25°C, where AS did not differ. The AS of both species acclimated to a variable thermal regime was similar at 15 and 25°C, but stonerollers had higher AS at the mean temperature of 20°C.
