At ovulation, the oocyte exits the gonad arm. In many species, maturation and ovulation are coupled. Ablation of the proximal myoepithelial sheath eliminates the contractions necessary to expel the oocyte from the arm. Ablation of the narrow distal spermatheca allows the oocyte to 'slip-back' from the spermatheca into the gonad arm following ovulation. We have isolated and mapped additional mutants with the Emo phenotype.
Endomitotic figures are most prominent in the very proximal portion of the gonad.
However, in other new emo mutants, such as oz138, oz198, and oz200, endomitotic figures extend further distally. Mating into oz138 females with wild type males results in a maternal effect embryonic lethality, but no Emo phenotype. The oz138 Emo phenotype is therefore dependent on oz138 sperm. In oz197, abnormalities are seen in chromosomal morphology in distal oocytes which are not yet endomitotic. This suggests a primary defects in meiotic prophase progression in this mutant rather than a defect in ovulation.