The Structure of the Spermatozoon of the Japanese Quail,Coturnix coturnix L., var. japonica

The spermatozoa of the Japanese quail conform, in their general ‘sauropsid’ plan, to that of other non-passerine birds. They are notable, however, in that the flagellum is very elongated (208 μm) and carries approximately 2,500 mitochondria in an extensive midpiece. Ultrastructurally, the acrosome and acrosome-nucleus junction is exactly as reported for other galliform birds. The neck region contains two centrioles arranged almost in-line; this unusual layout apparently occurs also in guinea fowl sperm. At the tip of the axoneme, beyond the termination of the central pair microtubules, is a structure—the tip granule—previously recognized in sperm of the domestic fowl. Trypsin digestion splits the axonemal cylinder, and the doublets then spiralize. This response has been reported before, in the sperm tails of other avian species.