Germinal cell loss in normal metazoan spermatogenesis

Abstract

A comprehensive review of the literature, of which a representative selection is given, reveals that a loss of developing germinal cells is a feature of spermatogenesis in general. The loss may be manifested by morphological, degenerative changes in single cells or in clones of cells at various stages of development, or in atypical spermatozoa ('polymorphism of spermatozoa') usually incapable of fertilizing an egg. The degree and the modes of the cell loss are species specific, but in general the abnormalities appear to originate during gametic mitosis and meiosis. They are associated with abnormalities in the division apparatus and the chromosomes. The hypothesis is suggested that the deviant and abortive gametes represent evidence of a mechanism of negative selection by which cells with certain undesirable characteristics are removed from the population. The nature of these characteristics is unknown.