Spermatogenesis in XY, XYSxra and XOSxra mice: a quantitative analysis of spermatogenesis throughout puberty.

Adult XYSxra mice exhibit varying degrees of spermatogenic deficiency but are usually fertile, while XOSxra mice have severe spermatogenic failure and are always sterile. The present quantitative spermatogenic analysis documents when these anomalies first appear during puberty. The results demonstrate that in XYSxra mice there was increased degeneration of pachytene spermatocytes and, to a lesser extent, meiotic metaphase stages. On average, there were only one-half the number of spermatids compared with the XY controls. The defect in XOSxra mice appeared a little later, with an almost complete arrest and degeneration during the meiotic metaphases, so that the number of spermatids produced was only 3% of the control value. These results are discussed in relation to an hypothesis that links sex chromosome univalence during meiotic prophase with spermatogenic failure.