ovo^D3/+ females carrying ovo^D1r+ produce embryos, but they die before hatching with gross and variable defects in cuticle differentiation including holes, especially anteriorly, segment deletions and fusions, failed head involution and deletions of anterior elements of the mouthparts.

Females carrying ovo^Δa in a wild-type or ovo^-/+ background are fertile.

Underexpression of ovo⁺ in females causes an extreme reduction in germ cell number. Most males bearing an extra 3 to 5 copies of ovo⁺ exhibit testes with wild type gross morphology and are at least semi-fertile. Nearly all males exhibit some spermatid cysts with defects. The most common defect is cells with a single large mitochondrial derivative surrounded by four spermatid nuclei, this is believed to be due to defects in the completion of cytokinesis during meiosis. Most rarely altered spermatid nuclei sizes are seen. Extra copies of ovo⁺ do not affect development of the male germline.