The salivary gland placodes of hkbA321R1 embryos appear identical to wild type. The first gross morphological defect seen is the incorrect positioning of the site of internalisation; the first cells to invaginate are those in the middle of the placode (in contrast to wild type where the first cells to invaginate are in the dorsal-posterior region of the placode). The invaginating pit is a mixture of wedge-shaped cells with constricted apices and basal nuclei, and elongated cells with randomly positioned nuclei (in wild-type all invaginating cells are approximately the same length and are wedge-shaped with basal nuclei). The pit is wider and shallower than in wild type and appears to include more cells. The invaginating salivary glands are trapezoidal shaped. The order of invagination is disrupted; cells immediately surrounding the pits appear to change shape and invaginate simultaneously. All secretory cells are eventually internalised, but the salivary glands are positioned more anteriorly and lie closer to the ventral midline and the body wall than the salivary glands of wild-type embryos. The characteristic cigar-shaped tubes of wild-type salivary glands are never formed, but the mutant salivary glands fuse along the ventral midline, forming dome-shaped organs with a commen lumen. Once invagination of the secretory cells is complete, open pits remain, as in wild-type embryos.
Mutant embryos fail to develop normal stomodeal nervous system ganglia, though remnants can be observed.