Mutant testes exhibit a meiotic arrest phenotype. They contain mature pre-meiotic primary spermatocytes, but not cysts undergoing meiotic divisions or attempting post-meiotic spermatid differentiation. Testes are smaller than wild-type because the lack of later stages of spermatogenesis. The arrested cells degenerate towards the distal end of the mutant testes. Mutant females are fertile.