The experimental induction of gynogenesis in the mouse. II. Ultra-violet irradiation of the sperm

Abstract

Sperm of the mouse, Mus musculus, was irradiated by ultra-violet light in vitro with dosages of up to 1.6 joules per sq.cm, then artificially inseminated into oestrous females. At $3\frac{1}{2}$ days' gestation, many haploid, hyper-haploid, hypo-diploid, hyper-diploid and mosaic embryos were found in addition to diploids. The haploids, hyper-haploids and hyper-diploids were very retarded in development, many of the hypo-diploids and diploids were normal or only slightly retarded. Ultra-violet irradiation interfered with the participation of the male chromosomes in syngamy, and occasionally suppressed the growth and differentiation of the male pronucleus. Many potential gynogenetic haploids degenerated without cleaving. Ultra-violet irradiation reduced the activity of sperm, and probably caused delayed penetration. After short exposures, considerable embryonic mortality occurred in presumably diploid embryos at implantation, and litter size was very small. One of the few offspring was deformed. Slight increase in exposure time completely suppressed implantation. These effects could have been due to induced changes in the sperm chromosomes. A theory of irradiation damage to the centriole or cytoplasm of the sperm in addition to the inactivation of its chromatin is postulated to account for the retarded development of the haploid and other embryos.