Testes from sec8^Z1010/Df(3R)Exel6145 flies show mild defects in spermatid elongation, and have bipolar cysts with axonemes growing from opposite directions. Plasma membranes separating individual spermatids are largely absent.

The majority (>89%) of fun^Z1010 mutant spermatids have one large nebenkern with four nuclei of normal size, indicating a cytokinetic failure in both meiotic divisions. A smaller proportion (8%) have two nuclei and a large nebenkern, indicating failure of only one of the meiotic divisions, while <2% of spermatids contain three nuclei, which may be due to failure of cytokinesis in the first meiotic division, followed by budding off of only one daughter cell in the second meiotic division. Further, a small amount of spermatids (<1% of cases) have more than four nuclei, which may result from defects in the mitotic divisions preceding mitosis. During early telophase of fun^Z1010 spermatocytes, there is an actin ring of normal appearance and and a normal central spindle. However, as telophase progresses the actin ring fails to fully constrict and the central spindle either becomes less dense or completely disorganized. The cleavage furrow initiates ~10 minutes after anaphase onset as in wild type, but shows a limited ingression and then regresses leading to a failure of cytokinesis.