Meeting Abstract
Extreme environmental temperatures pose significant metabolic challenges for ectothermic organisms such as teleost fishes. Recently, we documented that a population of Cyprinodon nevadensis amargosae pupfish inhabiting a thermal spring referred to as Tecopa Bore in the Death Valley region of California experienced an approximately 15°C increase in mean temperature between 2008 and 2013. Here, we evaluated the aerobic and anaerobic metabolic capacity of C. n. amargosae from Tecopa Bore (TB) and the neighboring Amargosa River (AR), a variable temperature desert stream, when acclimated to high (34°C) and low (24°C) temperatures. In light of evidence that fish from these differing temperature habitats vary in thyroid hormone physiology in the wild, we also examined how temperature influences the potential regulation of metabolism by thyroid hormones. We hypothesized that the effects of exogenous triiodothyronine (T3) on metabolism would vary with thermal experience. To this end, we measured citrate synthase (CS) and lactate dehydrogenase (LDH) activity as indicators of aerobic and anaerobic metabolic capacity, respectively, in skeletal muscle and liver tissues of adult C. n. amargosae from both the TB and AR populations. In muscle, there was a strong temperature effect on CS activity whereby fish from both populations held in the higher temperature exhibited lower CS activity. In the liver, CS activity was not altered by temperature or T3 treatment, but LDH was elevated in the AR population compared to TB fish and increased in both populations in response to T3. Detailed analyses are ongoing, but our early results point to population-level variation and T3 regulation of glycolytic enzyme activity, and temperature sensitivity in oxidative enzyme activity.
