Diplo XX ix5 homozygotes display variable degrees of intersexual characteristics, visible as incomplete and asymmetric development of the external terminalia and internal reproductive organs. The genital arch and anal plates are both affected, bristles are abnormal. Cell death is elevated in homozygous mutant genital discs.
When XX ix5/ix5 flies are reared at 18oC, the sixth and seventh sternite bristles can be female-like. In these flies, the male derivatives of the genital disc, genital arch and phallus apparatus are poorly formed. The anal plate can be laterally positioned as in the male, but remain fused. When XX ix5/ix5 flies are reared at 25oC, intersexual characters are seen with variable phenotypes. In some flies the terminal segments are not clearly differentiated. In these intersex flies, none of the male or female genital organs of the flies are developed and the anal plate remains undifferentiated. However, the segmental pattern follows the male pattern, despite a genital-arch like structure being developed. In some XX ix5/ix5 flies, simultaneous realization of both male and female developmental pathways was noted. When XX ix5/ix5 flies are reared at 29oC, both male and female genital primordia develop simultaneously. The terminal abdominal segment of the body develops differentiated intersexual characteristics in XX ix5/ix5 flies reared at 29oC. In these individuals, a rudimentary penis-like structure is seen. The morphology of the bristles of the terminal abdominal segments of all intersex XX ix5/ix5 flies is abnormal, although the penetrance and expressivity is variable. In XY, ix5/ix5 individuals sexual phenotypes are male except for the morphology of the bristles of the terminal abdominal segments. The female and male genital primordia develop simultaneously in the genital discs of XX ix5/ix5 larvae. In some larval genital discs of XX ix5 individuals, there is a loss of monolayer organisation. In addition, a large mass of chitinous outgrowth can protrude from the vaginal opening. In addition, a large mass of chitinous outgrowth can protrude from the vaginal opening ('genital knob'). The ix5 mutation is considered to cause disruption of cell lineages in the sex comb area of males. In some males the sex comb teeth are arranged in more than one row. In some flies, sex comb teeth are slender and pointed in appearance. An irregular and clustered arrangement of the sex comb teeth can be observed in some ix5 flies. Morphologically, the sex comb bristles are less masculinized. When ix5 males are reared at a restrictive temperature (29oC), the size of the gonads is reduced considerably. These males are also partially sterile. Orcein-stained squash preparation of testes from ix5 males raised at 29oC show an increased frequency of dense round sperm heads, instead of the long, narrow, condensed sperm heads of the wild-type male. XY, ix5/ix5 males elicit much less courtship than their control siblings. XX, ix5/ix5 are almost female-like in courtship behaviour.
Alteration of caetotaxal pattern of the basitarsus of the male foreleg. Homozygosity causes diplo X individuals to develop as intersexes. The external genitalia of these intersexes is variable.