mir-977^KO increases the viability of males, but not of females, as compared to controls. mir-977^KO hemizygous males crossed to control females produce significantly more progeny than control males, which is due to the stimulation of ovulation (i.e. a significantly increased egg production per mating) rather than increased embryo viability (i.e. number of eggs hatching is unaffected). Furthermore, mir-977^KO does not affect in the mating ability of mutant males with naive females, but results in a slightly higher reduction of female receptivity to re-mating, as compared to control males. The progeny of mir-977^KO males present a similar sex ratio as control progeny.