Trachea are absent in homozygous trh3 embryos, yet peripheral glial migration phenotype is normal.
In trh3 homozygous embryos, salivary duct cells fail to invaginate, instead remaining clustered on the surface of the embryo.
In mutant embryos, tracheal pits do not form, however, the metameric invagination that occurs producing a groove between the muscle precursors of adjacent metameres still occurs. However the gap between the most dorsal muscle precursors and the more ventral ones are missing.