When hh⁴/hh⁸ embryos are shifted from permissive to non-permissive temperatures for three hours during mid-stage 11 to stage 12, the majority have a short gastric caecum phenotype. While in about 10% one or few gastric caeca are lost and the size of those remaining is considerably reduced.

Mutants raised at 18^oC exhibit cuticle defects in the medial region of all three leg types. The region of tarsal segment 5 flanked by longitudinal bristle rows 1 and 8 show an almost complete loss of microchaetae. The distal-most sensory bristle is lost in 29% of legs. Mutant flies possess a normal pair of tarsal claws, and no appreciable difference is seen in claw-to-claw distance. hh⁴ flies raised at 20^oC lose about two scutellar bristles.

hh⁴/hh¹¹ ovarioles grown at 28^oC display severe germ-line defects. About 1/5 of ovarioles show obvious germ-line defects. Germ cells appear to differentiate precociously and become necrotic at very high frequency. In addition, somatic cells show under-proliferation defects.

Loss of hh activity at 6 hours of development in hh⁴ homozygous embryos results in the loss of 1-3^o cell fates in the dorsal epidermis (in wild-type embryos each parasegment contains 4 types of cells in the dorsal epidermis; the 1^o, 2^o and 3^o cells in the anterior half of the parasegment and the 4^o cells in the posterior half of the parasegment). Loss of hh activity at 7 hours of development in hh⁴ homozygous embryos results in production of a few 3^o denticles in the dorsal epidermis. In some segments an entire row of 3^o denticles is seen, but in most segments scattered 3^o denticles are mainly seen.

hh⁴/hh^lacZ flies have defects in the external genitalia. In males, the severity of the defects can be classed into 3 types. 20% of males show loss of the anal plates. The typical horseshoe shape of the male external genitalia is maintained with a distinct lateral lobe, posterior lobe and claspers in these flies. In about 20% of males the horseshoe shape of the external genitalia is replaced with an "α" shape, due to the absence of anal plates and a portion of the genital arch, leaving the lateral plates and claspers lying almost close together. Approximately 60% of males completely lack the anal plates and genital arch. The bristles of the lateral lobes, posterior lobe and claspers are fused together and are in the centre of the "α" shaped external genitalia. The penis apparatus shows less extreme defects; hypandrial processes are expanded and the apodeme is defective in approximately 20% of males. In females the external genitalia are less severely affected; the thorn bristles and long bristles of the vaginal plate show duplication, but all other structures are normal.

The hh⁴/hh⁸ combination is temperature sensitive: loss of hh function 6hrs AEL leads to loss of 1^o, 2^o and 3^o but not 4^o fates. Loss of hh function 7hrs AEL leads to loss of 1^o, 2^o but not 3^o and 4^o fates. In double mutants with ptc⁹, 1^o and 2^o cell types are restored. Loss of hh function 6hrs AEL leads to loss of 3^o fates. In double mutants with lin²/lin³ the 3^o cell type is restored.

When hh⁴/hh¹¹ females are grown at 18^oC and raised to 28-29^oC for 6-8 days, compound egg chambers are produced which result from the failure to encapsulate the germline cysts by the somatic follicle cells. Region 1 of the germarium appears normal but region 2 contains round germ-line cells amongst which individual cysts are difficult to distinguish. In the most extremely affected ovarioles a small germarium is attached to a giant chamber which contains all the cysts that would normally be separated into individual egg chambers. These effects are similar to those caused by neurogenic mutants. In addition, follicle cells in young egg chambers sometimes show an increased number of mitotic figures.

The critical period sensitive to hh activity is 1-2 hours (at 18^oC) prior to the delamination of neuroblasts 6-4 and 2-4. hh produced 6.5 to 8.5 hours AEL at 18^oC or 3 to 4 hours at 29^oC is necessary and virtually sufficient to form neuroblasts 6-4 and 2-4 normally. Results suggest the target cells for hh are not the neuroblasts but neuroectodermal precursors.

hh⁴/hh⁸ embryos raised at 29^oC throughout development exhibit a severely reduced heart, at 18^oC the number of heart cells is normal. Temperature shift experiments show heart formation is most sensitive between 3.5 and 4.5 hours of development.

Embryos exhibit a ventral cuticle phenotype.

When hh function is inactivated at 6 hours after egg laying, 1^o, 2^o and 3^o cell types are missing from the embryonic dorsal cuticle. When hh function is inactivated after 9 hours after egg laying the dorsal cuticle is unaffected. When hh function is inactivated at 7 hours after egg laying 3^o and 4^o cell types, but not 1^o and 2^o cell types, are specified. When hh function is inactivated at 8 hours after egg laying 2^o, 3^o and 4^o cell types, but not 1^o cell types, are specified.

Defective in gonad assembly.

Transheterozygotes with hh^A, hh^AC, hh^AE or hh^AM produce some adult survivors, at 18^oC transheterozygotes with hh^AC and hh^AE display an eye phenotype.

Embryonic viable at 18^oC and lethal at 25^oC with partial denticle belt fusions. In a su(w^a) background hh⁴ is embryonic viable and normal at 18^oC and 25^oC.

Weak hh phenotype: denticle belt fusions along the anteroposterior axis. Embryonic lethal at 25^oC and viable at 18^oC. Temperature shift analyses demonstrate the temperature sensitive period is between 2.5 and 6 hr of embryonic development and a larval/pupal period from 4 to 7 days of development.

Weak phenotype. Mutant embryos show fusions that delete the naked cuticle usually between abdominal segments 1 and 2 and 6, 7 and 8.

hh⁴ has embryonic epidermis | dorsal phenotype, suppressible by Wnt4^UAS.cGa/Scer\GAL4^da.G32

hh⁴ has dorsal denticle phenotype, suppressible by Wnt4^UAS.cGa/Scer\GAL4^da.G32

hh⁴ is a non-suppressor of imaginal disc phenotype of ci⁹⁴/ciⁿ

hh⁴ is a non-suppressor of leg disc phenotype of cg⁰⁷⁶⁵⁹