SPERMATOZOA: THE PROBABLE SELECTION OF A SMALL POPULATION BY THE GENITAL TRACT OF THE FEMALE RABBIT

Abstract

Summary. Spermatozoa recovered from rabbit uterus or oviducts, or from antibody columns, were mixed with freshly ejaculated spermatozoa of different genotype and inseminated into the uterus of a second doe, 9 to 12 hr before ovulation to allow time for capacitation. Forty-seven litters were produced. Spermatozoa from high in the female tract were individually more potent: 1·9×107 `unselected', 2·1×107 `chemically selected', 7×105 uterine, 1·6×104 oviducal spermatozoa were inseminated per offspring produced. If only spermatozoa represented by progeny were counted, the figures became: 1·6×107, 3·4×106, 2·7×105, 1·04×102, respectively. Logarithmic means, for litters calculated separately, were: unselected 6·61±0·19, chemically selected 5·92±0·42, uterine selected 4·91±0·45, oviducally selected 2·04±0·17. This is considered good evidence that part of the function of the mammalian female tract is selection of a few spermatozoa for fertilization. Possible reasons for such selection are considered, and the process is related to errors of chiasmata during spermatogenesis.