pyd^KG00264 embryos display defects in tracheal development including dorsal branch fusion problems, ectopic terminal cells, a lack of fusion cells, and ganglionic branch outgrowth defects. The dorsal branch phenotype is not fully penetrant; 2% of embryos show wild-type tracheal systems, 34% show defects in 1 metamere, 38% show defects in 2-4 metameres and 26% show defects in >5 metameres. Fusion defects are occasionally observed in the lateral trunk, although the penetrance of this is lower than for the dorsal branch.

The dorsal branches of pyd^KG00264 embryos show large loops of intercellular adherens junctions, indicating that cell intercalation is not complete. These intercalation defects are not fully penetrant.