In LacBG01462 homozygous embryos, the early events of tracheal development, such as guidance, primary branching, branch fusion and extension of terminal branches occur normally. However, from stage 15 onwards most branches become more sinuous or convoluted than in the wild-type; this is especially conspicuous in the dorsal trunk. The convoluted shape of the tracheal tubes is a consequence of having lengthened too much. However, this extra growth does not appear to derive from an increase in the number of embryonic tracheocytes, but rather from an increase in the length of the cells. Tracheal lumens in these embryos are uneven, particularly those of the dorsal and lateral branches, with expansions, constrictions and numerous lumenal breaks and discontinuities. Many lumenal breaks are the result from detachment of tracheal branches from one another. Cell detachments that break the tracheal tubes are found particularly in those branches where cells elongate more. Tracheal tubes in these embryos do not inflate at the end of embryogenesis. Trachea in late stage LacBG01462 homozygous embryos retain normal epithelial polarity, and normal polarization of the cytoskeleton. However, dye permeability assays show that these embryos are unable to establish or maintain the tracheal diffusion barrier. In these assays, dye is also internalized in the salivary glands, a phenotype not seen in wild-type. At late embryonic stages these embryos have necrotic tissue in the salivary gland region.