Structural characterization of procentrioles in Drosophila spermatids.

Male gametogenesis in insects is unusual in that the centrioles do not duplicate during the second meiosis and the differentiating spermatids inherit only one centriole. Here it is showed that a distinct procentriole is assembled close to the proximal region of the centriole in early S13 spermatids at the onion stage, confirming previous reports of a proximal centriole-like structure at the proximal end of the spermatid centriole. However, the procentrioles of Drosophila spermatids do not behave like true procentrioles, but their development is blocked at an early stage before the assembly of a complete A-tubule set. Therefore, they may represent early frozen stages of procentriole assembly that do not develop further and eventually disappear in late spermatids.