Detecting phenotypic impacts of elevated temperature on Amargosa Pupfish: An integrative approach

Authors: Lema, Sean C*1, Chow, Michelle I1, Resner, Emily J1, Westman, Alex A1, Dittman, Andrew H2, Hardy, Kristin M

Year: 2015 (xlvii)

Abstract

Fisheries Science Center). Amargosa pupfish, Cyprinodon nevadensis amargosae, in Tecopa Bore – a small thermal spring in the Death Valley region – appear to have experienced a decline in body size (e.g., 48% decline in mass) related to an increase in habitat temperature that began in 2010. This decline in body size was accompanied by the loss of one or both of the paired pelvic fins in 34% of the population. Previous studies found that exposure to elevated temperatures during larval life inhibits pelvic fin development and implicated altered thyroid hormone (TH) physiology as a potential mechanism mediating these effects. Investigating whether changes in TH physiology might link to the phenotypic changes detected for C. n. amargosae in Tecopa Bore, we documented elevated mRNAs encoding deiodinase type 3 (dio3) as well as depressed mRNA levels for deiodinase type 2 (dio2) and TH receptor β (trβ) in the liver of wild pupfish from Tecopa Bore compared to a nearby allopatric population of conspecifics in the Amargosa River. Wild adult pupfish from these two populations acclimated in captivity to 24°C or 34°C continued to show population-level variation in liver dio2 and dio3 mRNA abundance, and also exhibited differences in how temperature influenced TH regulation of lactate dehydrogenase activity (i.e., an indicator of anaerobic metabolic capacity) and metabolism-associated gene expression. These findings indicate that TH regulation of metabolism is dependent on thermal experience. For pupfish occupying habitats with dissimilar thermal regimes, these complex interactions between temperature, TH physiology and metabolism could shift the dynamics of energy balance and growth to contribute to the observed differences in body size and morphology between populations of C. n. amargosae.