Abstract
The semen from a Landrace boar which contained 13 -60% of the sharp folding deformity, called "hairpin curved sperm", was investigated on the inner structure.Inside of the serial plasma membrane, the folding characteristically occurred at the caudalarea of the middle piece, average 10th of the mitochondrial profile from the annulus(Jensens ring). In the cross section, a pear-shape profile containing a cut surface of themiddle piece and a principal piece which showed an opposite direction of the axonemalconstruction occurred. The possible etiology of this deformity was briefly disscused inthis report.
