The posterior half of the abdomen is folded back on the anterior half, due to a failure of germband retraction, resulting in an eponymous phenotype. At full germband extension A8 is often opposite A2. Head involution fails. Some components of the head skeleton are absent or rudimentary, including the dorsal arms, dorsal bridge and vertical plate. The filzkorper are often separated, though less so than for ush mutants. An anterior dorsal hole is also sometimes evident. peb mutants often show a head-back phenotype. Anti-β-tubulin staining reveals a premature loss of amnioserosa cells after stage 11. The amnioserosa undergoes programmed cell death.
Within constraints of the embryo being folded due to the hnt mutation, the muscle pattern is normal and movement is vigorous and well coordinated.
Longitudinal tracts are interrupted. Intersegmental gaps show in glial scaffold and in the midline, the glial scaffold retracts after initial extension, though the longitudinal glial morphogenesis is abnormal.
Suppression of tor13D embryos: increase in proportion of embryos that formed cuticle with denticles and decrease in proportion of embryos that formed empty sacs.