Abnormal human spermatozoa including comparative data from apes

Several reports have shown that the sperm counts in man have declined over the last 20 years. Human spermatozoa also exhibit a structural and chemical variation that is greater than that of most other mammals. Human fecundability is low compared with other examined animal species. Possible causes of these three classes of findings are analyzed: The effect of clothing or of other undue heating of the scrotum; xenobiotic influences such as smoking, lead compounds, X-rays, alkylating agents; degeneration effects, and mating habits. Comparative data from the great apes are of interest, as spermatozoa from the gorilla but not from the chimpanzees and orangutan show a structural variation similar to that of human spermatozoa. A classification of the different types of abnormal spermatozoa is given and the possible causes-genetic or environmental-for each subgroup of abnormal sperm pattern are presented.