Spermatids from both Rab1^Z4144/Rab1^S147213 and Rab1^Z4144/Df(3R)ED10838 transheterozygous males display cytokinesis defects and contain multiple nuclei associated with enlarged nebenkern mitochondrial derivative. In contrast to wild-type controls, Rab1^Z4144/Df(3R)ED10838 spermatocytes at mid-late telophase as well as larval neuroblasts frequently show unconstricted and fragmented contractile ring (as visualized by zip staining). The lva positive bodies in the mutant spermatocytes are more numerous but smaller and on the ultrastructural level their Golgi apparatus stacks appear collapsed with fragmented cisternae and a large number of associated small vesicles. Adult lifespan of Rab1^Z4144/Df(3R)ED10838 flies is significantly reduced compared to controls.

Both omt^Z4144 homozygotes and omt^Z4144/Df(3R)e-F1 mutants have spermatids with one large nebenkern and four nuclei of normal size, indicating a cytokinetic failure in both meiotic divisions. At a lower frequency, both mutants also contain spermatids with two nuclei, indicating failure of only one of the meiotic divisions. During early telophase of omt^Z4144 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. omt^Z4144/Df(3R)e-F1 mutants show the same phenotype.