The occurrence of a "SME"-defect-like abnormality in the head of spermatozoa from a Norwegian Landrace boar.

A spermhead-defect appearing in 15-20 per cent of the spermatozoa from a Norwegian Landrace boar with a slightly impaired fertility was studied in light and electron microscope. The defect had the shape of a circumferential, somewhat elevated area containing a cystic structure located within the nucleus. In some of the sections observed in electron microscope a communication could be found between the cyst and the acrosome, indicating that a deviating development of the latter could be involved in the formation of the defect. In some spermatozoa the occurrence of the cyst was combined with the presence of an apical defect of the acrosome. From ultrastructural studies of spermatids the development of the cystic defect was found to have reached a rather advanced stage early in the acrosome-phase of the spermateliosis. As a whole the observations correspond very well with those made in connection with the socalled "SME"-defect first found in a Danish Landrace boar.