Heat induced expression causes a drop in the embryo hatching rate. Unhatched embryos show a muscle pattern defect due to severe perturbations in muscle tendinous cell attachment creating the characteristic spheroidal muscle morphology. Cytoarchitecture of the spheroid muscles reveals a lack of defined Z bands and the muscles are significantly disorganised compared to wild type. Embryos with less drastic muscle perturbations can generate hatching movements and hatch with a time delay. Larvae are less active than wild type and exhibit perturbations in locomotor behaviour. They develop but do not grow in size. Larvae show perturbations in somatic muscles, they are attached to the epidermis at the apodeme sites but are very short and have a stretched appearance. Perturbations in visceral musculature are also seen; visceral muscles separate from each other and are no longer elongated. In mutant adults the leg tendon is absent.

Embryos carrying Cg25C^del.hs show a small to moderate rate of non-hatching in the absence of heat shock, non-hatching is significantly increased by a single 30 minute heat shock. Unhatched embryos show severe defects in morphogenesis, especially in germband shortening and dorsal closure and may also have head defects. 18% of hatched larvae have a hole in the dorsal cuticle. Hatched larvae may also show incomplete germband retraction. The nerve cord does not contract in mutant larvae, is flattened and does not appear to be separated from the epidermis. In the median and posterior parts of the larva it surrounds the internal organs. The supraoesophageal ganglia and presumptive optic lobes are not condensed.