Nuclear shaping in spermatids of the Thai leaf frog Megophrys montana.

Transmission electron microscopy of Thai leaf frog testis revealed a unique pattern of spermatid nuclear morphogenesis. Chromatin condenses into a continuous cylindrical coil within a roughly spherical nucleus. Later the nuclear membrane conforms to the contours of the uncoiling nuclear contents. In the mature sperm, the long, tapering nucleus is helically shaped. This developmental sequence occurs in the absence of a microtubular manchette, raising questions about the role of this structure in nuclear shaping in spermatozoa of other species.