Meeting Abstract
Environmental variation can impact patterns of gene expression and contribute to phenotypic differentiation among populations. Pupfishes (genus Cyprinodon) inhabiting the Death Valley region of California and Nevada, USA, occupy a collection of remote aquatic habitats that vary widely in ecological conditions. Previous work on these taxa has shown that exposure of pupfish to elevated temperatures (e.g., greater than ~30°C) during early life leads to altered body shape and a developmental loss of the paired pelvic fins, and pointed to such morphological changes as being related to altered thyroid hormone signaling. We therefore hypothesized that pupfish living in extreme thermal environments would exhibit altered patterns of thyroid hormone production, metabolism or tissue sensitivity. For this study, we collected Amargosa pupfish Cyprinodon nevadensis amargosae from two geographically isolated habitats in the Death Valley region: the Amargosa River, a thermally variable habitat, and Tecopa Bore, a hot spring and associated marsh where pupfish occupy waters exceeding 37°C. Gene expression related to thyroid hormone signaling was quantified in collected fish using quantitative real-time RT-PCR. Our data indicate that the relative abundance of gene transcripts encoding iodothyronine deiodinase enzymes type 1 (dio1), type 2 (dio2), and type 3 (dio3) in the gill epithelium are consistently elevated in both male and female pupfish from the hot spring habitat. Transcript encoding thyroid hormone receptor αB (trαB) was also found to be at higher relative levels in the gill of pupfish from the hot spring. These findings suggest that populations of pupfish occupying habitats with distinct thermal profiles may show divergent gene expression patterns for deiodinase enzymes and thyroid hormone receptors.
