Up to 2% adult escapers are seen among crc1 hemizygotes. Mutants show several lethal phases during larval, pupal and adult development. Hemizygotes show 15-50% of their lethality after pupariation. Hemizygous puparia are generally aberrant to varying degrees (approximately 5% are indistinguishable from wild type). The defects include a failure to evert the anterior spiracles, and a retention of a larval shape, which is thinned, elongated and sometimes curved to one side. In the most severe cases, the abdominal gas bubble, which normally forms approximately 6 hours after pupariation, does not appear, although the larval mouthparts are later expelled. Head eversion fails or is incomplete and the leg and wing discs do not completely elongate. Segmentation and differentiation of the abdomen usually fail, although in some cases the anterior abdominal segments differentiate. Other aspects of adult development proceed normally, resulting in the appearance of mature eye pigments and darkened macrochaetae and differentiation of the wings and legs. Hemizygous females show markedly reduced fecundity. 5-10% of hemizygous adults fail to expand their wings and fully tan the adult cuticle. Other hemizygous adults show more subtle defects involving the wings, legs, scutellum, scutellar bristles, halteres and dorsal thorax.
Low rate of chitin deposition during prepupal chitin deposition period. Studies of pupal cuticles suggest that crc1 homozygotes are unable to evert their cephalic complexes at pupation. Total chitin content studies of the pupal cuticle cannot exclude the possibilty of specific increases in chitin content of the head and anterior thorax region.
Head eversion is totally or partially suppressed, wings and legs are shortened, abdomen is longer than normal. Homozygotes die within the puparium after completion of imaginal development.
Homozygotes frequently die as larvae; failure to eliminate chitinous mouthparts at the larval molt frequently results in larvae with supernumerary mouth parts; homozygotes undergo pupation but rarely eclose from puparia. Imaginal head is not everted from thorax. Except for slightly reduced eyes and shortened legs, wings and thoracic bristles, the head and thorax are fully differentiated; frequently fail to pass gas bubble to anterior retro-opercular position, thus failing to provide space for head eversion. Head eversion is inhibited by integument being more rigid than normal. Mutant integument contains more glucosamine than normal; Sparrow and Chadfield (1982) unable to confirm. Feeding glucosamine to wild-type larvae produces a phenocopy very similar to crc. Abdomen often shows no differentiation and internal organ development is arrested at pupal stage. Lethality suppressed by su(crc)1 (Sparrow, 1981). RK3.