The Human Spermatozoon — Not Waving but Drowning

Abstract

The human male produces the poorest quality semen of all mammalian species studied to date. This alarming fact is illustrated by the World Health Organization’s recent reference text on human seminology (World Health Organization, 1999) which suggests that up to 85% of spermatozoa may be morphologically abnormal, even in the fertile male population. The abnormally shaped spermatozoa that appear endemic to our species also seem to possess a diminished capacity for fertilization, given that defective sperm function is the commonest, defined cause of human infertility (Hull et al., 1985). The morphological abnormalities that dominate the human semen profile may take many forms, but retention of excess residual cytoplasm in the midpiece of the spermatozoa and defects in the acrosomal region appear to be particularly important (Keating et al, 1997; Garrett et al., 1997). Impaired sperm motility, asthenozoospermia, is another common cause of defective human sperm function. This is a very dynamic aspect of sperm biology that is particularly susceptible to environmental interference, such as workplace exposure to organic solvents (Wang et al., 2001; Xiao et al., 2001). In the wake of such defects in semen quality, the human species is distinguished by a higher rate of spontaneous abortions and birth defects than any other mammal. In light of such data, it is difficult to avoid the conclusion that something is seriously wrong with spermatogenesis in the human male.