Expression of zip^hs.P using heat shock in adult males has little overall effect on viability or sperm production. Overexpression of zip^hs.P during spermatogenesis results in minor defects in developing spermatid bundles; nuclei are seen scattered along the length of the cyst in elongating spermatid bundles (in contrast to wild type, where they are localised apically). These defects are present prior to spermatid individualisation.

When heat shocked males expressing zip^hs.P are crossed to wild-type females, there is a significant increase in the proportion of unhatched eggs compared to when non-heat-treated males carrying zip^hs.P or heat-treated wild-type males are crossed to wild-type females. Fertilised eggs derived from a cross of heat shocked males expressing zip^hs.P and wild-type females show numerous chromosomal abnormalities. If the females in these crosses are infected with Wolbachia, there is no rescue of the phenotype, and the proportion of unhatched eggs is increased.