Homozygous males are sterile but have highly motile sperm which do not show any obvious morphological abnormalities. csn^HB156 males mate normally with virgin wild-type females and the csn^HB156 sperm is transferred normally to the females at mating. However, eggs laid by these females never hatch. In addition, analysis of the eggs show no evidence of the presence of zygotes, cleavage stages or embryos, and there is no evidence for the presence of sperm nuclei inside these eggs. It therefore appears that the sperm of csn^HB156 males are incapable of entering the egg. Hemizygous males have phenotype identical to that of homozygous males. The male reproductive system appears normal in homozygous and hemizygous males. The acrosome, nucleus and all the components of the tail of the spermatozoa are also normal.

Mutant males produce morphologically normal and motile sperm. The mutant sperm is transferred to females.