One copy of Psi^ΔAB in a Psi^v16 homozygous background induces male abnormal courtship behavior, in particular longer duration of wing extension, difficulty initiating song production, and increase in copulation attempts as compared to controls.

Psi^v16 males partially rescued by Psi^ΔAB show courtship defects. The courtship index of these males is 60% (compared to 75% in controls). Also only 30% of mutant males copulate over a 30-min period and these matings yield no progeny. In two-thirds of the lines examined, spermatid cysts are disorganised and spermatid bundles are intermingled. Postmeiotic onion stage early spermatids are often multinucleate and contain atypical large mitochondrial derivatives. Abnormal spermatids start to differentiate but fail to mature, and no sperm are stored in the seminal vesicle. In other lines, almost no postmeiotic cells are observed. No bundles of spermatids are formed, and large cells similar to undifferentiated premeiotic spermatocytes fill the testes.