Morphological abnormalities in spermatozoa of man and great apes

Abstract

HUMAN semen has long been known to differ from that of any other mammal in the high proportion of abnormal spermatozoa that it contains¹. But there has been almost no opportunity to compare human spermatozoa with those of man's closest living relatives, the chimpanzee (Pan troglodytes), the pygmy chimpanzee (Pan paniscus), the gorilla (Gorilla gorilla) and the orangutan (Pongo pygmaeus); these are all now endangered species, and the few animals in zoos are not available for experimentation. Recently, workers at the Yerkes Regional Primate Research Center, where all four species are maintained, have perfected a technique for obtaining semen from these rare animals by electroejaculation². Preliminary studies have suggested that marked morphological similarities exist only between the spermatozoa of the gorilla and man³. We examined these similarities and differences in more detail, in the hope that spermatozoal morphology might provide some taxonomic clues about our affinities to the great apes.