Stage 12 Dfd16/Dfd12 embryos show displacement of the maxillary segment and mandibular segments due to an accumulation of supernumerary cells at the ventral side of both segments. Cells in the ventral part of the maxillary segment are elongated, instead of round like wild-type cells.
In Dfd12/Dfd16 embryos, the maxillary cirri primordium and the anterior boundary of the dorsal ridge, between the mandibular and maxillary segments, are missing. The number of apoptotic cells in the maxillary segment is reduced when compared to wild-type.
Dfd12/Df(3R)Scr embryos lack the mouthhooks and cirri, while the more posterior mouthparts are unaffected. The mouthhook and cirri defects are rescued in Dfd12/Df(3R)Scr embryos expressing DfdScer\UAS.cBa under the control of Scer\GAL469B. Head involution fails in these animals and the posterior mouthparts fail to form. Dfd12/Dfd16 embryos lack the mouthhooks and cirri, while the more posterior mouthparts are unaffected.
Mouth hook material is in a position posterior to wild type and rarely possess maxillary cirri: defects in structures derived from the maxillary, mandibular and premandibular regions of the embryonic head. Mitotic recombination analysis suggests that in the adult Dfd affects the head structures homologous to those of the embryo.