Dsim\Nmy¹⁴²⁷ males show sex ratio distortion; the progeny of such males show a female-biased sex ratio. The expressivity of the sex ratio distortion is inversely correlated to the temperature; at 18[o]C, the sex ratio of the progeny can reach as high as 93%, whereas at 25[o]C, the sex ratio decreases to approximately 60%. Only the temperature at which the males are reared has an effect on the sex ratio distortion. The age of the males also has a much smaller, but also significant, effect on the sex ratio distortion.

Dsim\Nmy¹⁴²⁷ males show abnormalities in various stages of spermatogenesis. The mutant spermatid nuclei start to accumulate nucleoplasmic vacuoles at the late onion stage. At the early elongation stage, some mutant spermatid nuclei have very pronounced nucleoplasmic vacuoles, although the alignment of rows of microtubules along the fenestrated portion of the nuclear membrane appears normal. Later, in the post-elongation period, nuclear condensation appears disrupted, and rupture of the nuclear membrane is sometimes seen. During individualisation, the nucleoplasmic vacuoles within abnormal mutant spermatids are squeezed into the tail region, apparently causing physical difficulty for the cystic bulge to pass through. These abnormal tails remain in the syncytium, which other tails are individualised and separated.