I-17: The Importance of Animal Sperm Modelsin Understanding Human Male Fertility/Infertility

Male fertility assessment is performed in the context of WHO guidelines. Currently the 5th edition of the WHO guidelines have been published and technicians and clinicians are confronted with a new set of criteria. Apart from coming to grips with these criteria it is accepted/assumed that human fertility is declining? However, both aspects are debatable. The accuracy/consistency of semen evaluation according to WHO can only be considered as a course measure for the potential of male fertility. Secondly, evidence that male fertility is declining globally is debatable since most semen analysis represents examples of patients that visit fertility clinics. Furthermore, more infertility clinics and better access to these clinics would in principle provide a biased semen sample. It may then be argued which alternatives are available to study the problem of male fertility? The hypothesis developed in this study is that human semen quality should be viewed in the context of the evolution of sperm competition. Which animal models provide a model for studying human infertility? Two models have been selected for this study. Firstly, the naked rodent mole which is the only eusocial mammalian species. This model is one which represents major stress in the colony and most males are rendered sub-fertile except for the breeding male. Secondly, animals as diverse as dolphin and elephant provide extreme cases of sperm competition and in the case of the dolphin also promiscuity. In bottlenose dolphin there ap-pears to be extreme sperm competition with about 95% normal sperm and above 90% motility. Naked rodent moles experience a considerable amount of stress and this is very well reflected in their very poor/ semen/sperm characteristics. Of particular interest is that they also have a very low percentage abnormal sperm and low percentage motility (like in humans). In contrast, dolphins have >90% normal sperm morphology and >80% motility. Furthermore, in elephant and rhinoceros semen parameters in general are also excellent when field conditions are good. It is proposed that human sperm characteristics be viewed in an evolutionary context. The low level of promiscuity in humans may have selected against the basic principles of sperm competition and accordingly sperm characteristics are poor. It is proposed that the “general poor quality of human sperm” does not necessarily represent poor quality sperm but is a consequence of evolutionary selection. Many different animal models assist to understand sperm quality in a phylogenetic context.