Meeting Abstract
Epidermal appendages (EAs) are a defining characteristic of vertebrates, and their evolutionary success may be credited, in part, to the developmental elaboration of these structures. One common EA is the scales of fish. While we have a solid grasp of how scales develop, as well as the developmental cues that differentiate scales from other EAs, little is known about the genetic mechanisms that underlie variation in scale shape. Such variation is likely to be important across species adapted to different habitats, as well as within an animal where serially homologous scales may be under different selective pressures at different points on the body (e.g., streamlining anteriorly, protective posteriorly). Using an F2 mapping cross between cichlid species with different scale phenotypes, we identified >40 quantitative trait loci (QTL) for numerous measurements of scales from distinct positions on the fish. We found that while certain regions of the genome regulate variation in multiple scales, most are specific to scales at distinct points along the anterior-posterior axis of the body, which suggests a degree of genetic modularity in scale development. We also identified a QTL for scale shape disparity, which suggests that shape variation across serially homologous scales has a tractable genetic component. Finally, using population genomics, we screened QTL intervals for candidate genes, and identify many previously implicated in EA development, including components of Fgf, TGF-beta, and Ephrin signaling pathways. These data suggest that the same genes involved in scale development might also mediate scale shape.
