Abd-BD18 mutant embryos show a significant increase in the number of (Dpn-positive) neuroblasts in the ventral nerve cord segments A9-10, show a significantly increased mitotic index of neuroblasts in the ventral nerve cord segments A9-10 and show significantly increased mitotic index of neuroblast daughter cell in the ventral nerve cord segments A8, as compared to controls.
Mutant embryos generate an additional cluster of eve positive mesodermal cells in PS 13. Supernumerary cardioblasts are also seen in the heart portion of the dorsal vessel of late stage embryos: about 116 cardioblast nuclei are seen as opposed to 104 in the wild-type. The heart in these embryos do not appear to be significantly elongated, it is frequently much wider and extra cardioblasts are arranged in irregular clusters or double-rows within its posterior portion. The somatic muscles in abdominal segment 8 in mutant embryos show an increase in the number of nuclei, and a pattern that is more similar to that normally found in A7.
Heterozygous flies show no transformation of A7 towards A6. The phenotype of abdominal segment 6 is similar in Abd-BFab7-1/Abd-BD18 and Abd-BFab7-1/+ flies.