Meeting Abstract
The pharyngeal skeleton of bony fishes is an exquisitely evolved foraging structure, with nearly every bone along the buccal cavity modified to directly interface with prey items. The gill rakers (GRs) and pharyngeal jaws (PJs), in particular, are critical for filtering and processing food. These structures are highly diverse across teleost lineages and vary according to foraging niche. Moreover, plasticity of the pharyngeal skeleton in response to diet shifts has also been noted for several species. The relative contribution of genetics and the environment in shaping the pharyngeal skeleton remains poorly understood. Here we explore the gene-by-environmental effects on cichlid GRs and PJs by rearing both pure bred species and their F3 hybrids in different foraging environments. We find that anatomical differences between species are dependent on the environment, owing to one species exhibiting a greater degree of plasticity than the other. Further, the genetic architecture of these traits is largely distinct between foraging environments. We did, however, note several “hotspots”, whereby multiple pharyngeal skeletal traits map to a common genomic region. One of these, for GR number, maps to the ptch1 locus, previously implicated in cichlid oral jaw shape and plasticity. Since Hedgehog (Hh) signaling has not previously been implicated in GR development, we explored functional roles for this pathway in the zebrafish model. We show that the Hh pathway is both necessary and sufficient to maintain plasticity in GR number. These data provide novel insights into the gene-by-environmental effects that shape key aspects of the cichlid feeding apparatus.
