Some aspects of spermiogenesis in a lizard

Abstract

Abstract Spermatids of the American chameleon Anolis carolinensis , have been examined with the electron microscope during the period from the first appearance of caudal sheath microtubules to the stage of differentiation just before the caudal sheath disappears. The caudal sheath microtubles are arranged initially in the form of a helix with a very low pitch. As the condensation of the chromatin and the elongation of the nucleus proceed, the caudal sheath helix unwinds. Shortly before the caudal sheath disappears, the sheath microtubles are oriented parallel to the longitudinal axis of the nucleus and the sheath resembles those found in other vertebrate spermatids. Assuming that the caudal sheath is functionally related in some way to the changes that occur in the nucleus, it is proposed that the unusual arrangement of the caudal sheath in A. carolinensis spermatids is a device to avoid a large excess of microtubules clustered around the nucleus at the end of nuclear elongation.