Mutant salivary glands of stage 16 embryos show three overt ultrastructural changes compared to wild type; the lumen of the salivary gland is significantly smaller than normal and is accompanied by reduced amounts of electron-dense luminal material, the mitochondria are concentrated to a region apical to the nucleus (in contrast to wild type, where they are distributed throughout the cell) and secretory vesicles are much fewer in number and smaller than those of wild-type salivary gland cells.

Analysis of embryos derived from homozygous female germline clones indicates that maternal loss of CrebA does not exacerbate the zygotic mutant phenotype.

CrebA^wR23 homozygous mutants exhibit significantly less secretory granules in the salivary glands compared to CrebA^wR23 heterozygotes. CrebA^wR23 mutants have major defects in cuticular development; the larval cuticles are smaller (on average only 40-50% the length of wild-type) and weaker than the cuticles of their wild-type siblings, the mouthparts and filzkorper are poorly formed, and CrebA^wR23 mutants frequently have large holes in the dorsal cuticle. In addition, there appears to be a general defect in patterning of the cuticle, with dorsal and ventral structures appearing more lateralized. The ventral cuticle exhibits a loss of denticles and the denticles that are present have a very light pigmentation, more consistent with the pigmentation found in more lateral denticles of wild-type larvae. The dorsal surfaces of the mutant larvae consist of thin hairs and naked cuticle, an arrangement more typical of dorsal-lateral reiogns of wild-type cuticles. The process of dorsal closure appears to be lagging in CrebA^wR23 mutants compared to wild-type.

Homozygous larvae are 40% the length and the same width as their heterozygous siblings, length differences arise during larva formation as embryos are about the same length as their heterozygous siblings. The larval cuticle of homozygotes is weak, as seen by frequent holes at random positions in the exoskeleton. The dorsal and ventral larval cuticle is composed of pattern elements found in the ventrolateral position in the wild-type larval cuticle. In spi¹; CrebA^wR23 double mutants the denticle bands are narrower than in spi¹ larvae and still exhibit some fusion of denticle rows between segments.