A Comparative Overview of Mammalian Fertilization

Abstract

The domestic cat is a member of the order Carnivora, a taxon consisting of 231 species, most of which exhibit vastly different reproductive strategies. The data base on sperm and oocyte interaction is poor for almost all carnivores. However, the mechanisms of fertilization for the domestic cat are beginning to receive attention because these studies generate new information of both fundamental and applied benefit. Unlike most conventional laboratory species, which ovulate spontaneously during estrus, the cat is an “induced” ovulator. Ovulation occurs only after multiple copulations trigger pituitary release of sufficient amounts of luteinizing hormone (LH), which causes final maturation of follicular oocytes. Therefore, the cat is useful for studying the kinetics of LH effects on oocyte nuclear maturation. It also is possible that induced ovulatory species have different mechanisms for sustaining oocyte viability in the ovarian follicle. If for some reason copulation is delayed in the estrous cat, then, in theory, the intrafollicular oocyte must innately sustain its longevity, moreso than in most mammals, which ovulate spontaneously near the onset of sexual receptivity.