Striated muscles that enable mouth opening and swallowing during feeding are essential for efficient energy acquisition, and
are likely to have played a fundamental role in the success of early jawed vertebrates. The developmental origins and genetic
requirements of these muscles are uncertain. Here, we determine by indelible lineage tracing in mouse that fibres of sternohyoid
muscle (SHM), which is essential for mouth opening during feeding, and oesophageal striated muscle (OSM), which is crucial
for voluntary swallowing, arise from Pax3-expressing somite cells. In vivo Kaede lineage tracing in zebrafish reveals the migratory route of cells from the anteriormost somites to OSM and SHM destinations.
Expression of pax3b, a zebrafish duplicate of Pax3, is restricted to the hypaxial region of anterior somites that generate migratory muscle precursors (MMPs), suggesting that
Pax3b plays a role in generating OSM and SHM. Indeed, loss of pax3b function led to defective MMP migration and OSM formation, disorganised SHM differentiation, and inefficient ingestion and
swallowing of microspheres. Together, our data demonstrate Pax3-expressing somite cells as a source of OSM and SHM fibres, and highlight a conserved role of Pax3 genes in the genesis of these feeding muscles of vertebrates.