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Under optimal conditions (20-30 isolated homozygous larvae per vial) about 60% of Dp(3;3)Karel homozygous larvae reach the third instar. Development during the third larval instar is significantly delayed (wandering homozygous larvae appear about 2 days after their heterozygous siblings) and some homozygous third instar larvae can be found alive even after 10 days of development. Dp(3;3)Karel homozygous third instar larvae show fat body disintegration and have multiple melanotic tumours, predominantly in the caudal part of the body and accompanied by disintegration of the fat body. Melanisation of the lymph gland is not seen in these larvae and the imaginal discs and brain appear normal. The overall structure of the ring gland appears unaffected. Less than 30% of Dp(3;3)Karel homozygotes eventually pupate. Homozygous pupae usually die soon after pupariation, in some cases they develop normal head and thorax imaginal structures, but abdominal parts do not usually develop. The pupal abdomen has an abnormal curvature to the right. Less than 2% of Dp(3;3)Karel pupae develop normally and eventually emerge as adults. These adults do not have any obvious abnormalities besides the abdominal curvature, although some are sterile. Dp(3;3)Karel homozygous early third instar larvae contain a much higher number of "sessile hemocytes" (hemocytes attached to the tissues under the integument) than wild-type controls. Dp(3;3)Karel homozygous late third instar larvae contain an average of 7-fold more hemocytes in circulation than wild-type larvae. More than 75% of the mutant hemocytes are strongly adhesive when placed on a substrate (in contrast to wild-type larval plasmatocytes which remain rounded) and after being placed on a drop of hemolymph on a microscope slide, they develop filamentous and membranous extensions. 7% of the mutant hemocytes are lamellocytes (a cell type that is not present in the circulation of wild-type larvae under normal conditions) and the mutant larvae also contain excess crystal cells compared to wild-type. The lymph glands of the mutant larvae appear dispersed in the late third instar (dispersal of the lymph glands normally occurs during metamorphosis). Pupariation frequency in Dp(3;3)Karel mutants is restored to almost wild-type levels by treatment with 20-hydroxyecdysone, and the delay in development is also significantly reduced.
