This segment pattern closely resembles that found in the A1 segment of zygotic exd larvae and is the same overall pattern observed after heat shock-inducing Ubx expression in zygotic exd embryos. The affected Ch neurons remain associated with the dorsal PNS cluster, or occasionally, are positioned between the dorsal and lateral PNS clusters. The orientation of the affected neurons is also abnormal. Whenever the affected LCh5 neurons remain associated with the dorsal PNS cluster, their dendrites point ventrally or posteriorly instead of dorsally. The 'dorsal chordotonals' phenotype can be detected in all the abdominal segments in varying frequencies.
Stronger alleles affect all the abdominal segments in similar frequencies.
Weak hth alleles do not affect any PNS neurons other than the LCh5 neurons. Strong hypomorphic mutations in hth affect not only the position and orientation of the LCh5 neurons, but also cause a reduction in their number. In spite of their abnormal location and orientation, the affected Ch neurons appear fully differentiated, as judged by their overall morphology and the presence of normal-looking scolopales at the tips of their dendrites. The precursors of the LCh5 neurons are born in a normal dorso-lateral position in hth mutant embryos. A similar phenotype was observed in embryos homozygous for mutations in the homeotic selector gene abd-A .