Homozygous males have an apparently normal reproductive system, which contains elongate bundles of maturing spermatids, but there are no motile sperm in the reproductive tract (although apparently mature sperm heads are present in these males). No sperm are transferred to females during copulation. The earliest defect in spermiogenesis in homozygous males is a failure of cytokinesis following meiosis. The primary spermatocyte undergoes nuclear division, resulting in four nuclei. Cytokinesis fails, resulting in four spermatids developing within a common cytoplasm. The mitochondria fuse, usually forming a single large nebenkern, rather than the four smaller nebenkern that would normally form in wild-type spermatids. This large nebenkern then first divides into two approximately equal bodies which have irregular shapes and show contact with the membrane sheaths surrounding the four axonemal complexes. The derivatives may then divide further, giving as many as 8 mitochondrial derivatives in a common cytoplasm. Odd numbers of mitochondrial derivatives are often seen suggesting that there is not a synchronised series of divisions within the cytoplasmic unit following the initial division of the nebenkern. As elongation begins, differentiation appears nearly normal except that the components of four spermatids are seen in each cytoplasmic unit. Acrosomes and centrioles establish normal contact with each nucleus. The mitochondrial derivatives appear to undergo normal elongation, despite being unusually large. Microtubules extend both anteriorly around the nucleus and posteriorly around the axonemal complex and mitochondrial derivatives, as in wild type. At the stage when the paracrystalline body begins to form, the mitochondrial derivatives are variable in size and rather irregular in shape. The paracrystalline bodies form at each point of contact between the primary derivative and the membranes around the axoneme. A single primary derivative may establish up to four contacts, and a single axoneme may contact more than one primary derivative, resulting in multiple paracrystalline bodies within the mitochondrial derivatives. At later stages, massive degeneration is seen in the spermatids.

Incomplete cytokinesis and ring-canal formation occur normally during meiosis in homozygous mutant males, however, furrow membranes subsequently fuse and disintegrate; double-membrane fragments and ring canals are found freely floating in the spermatid cytoplasm.