Meeting Abstract
Hormone systems can act as mechanistic links between an organism’s external environment and its internal physiological processes. When environments change, alterations in hormone signaling pathways may shift phenotypes rapidly via impacts on patterns of gene expression and, ultimately, development. Recently, we identified a population of Amargosa pupfish Cyprinodon nevadensis amargosae that experienced a decline in body size (e.g., 48% decline in mass) related to an increase in temperature that began in 2010 in their habitat, Tecopa Bore – a small thermal spring. This decline in body size was accompanied by the loss of 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) status as a potential mechanism for these effects. Investigating that possibility, 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 in the cooler Amargosa River. The maintenance of adult pupfish from these two populations in captivity at 24°C or 34°C revealed that temperature influences on liver dio2 and trβ transcript abundance differed between populations, and that populations varied in how metabolism-associated gene expression responds to exogenous TH. These findings point to complex interactions between thermal experience, TH signaling and metabolism as contributing to energetic changes associated with morphological differentiation of C. n. amargosae.
