Spermiogenesis ofLacerta vivipara

Abstract

To the common aspects of spermiogenesis in Reptilia, several new organelles are described in the lizard. One or two nuclear pouches, formed by the invagination of the nuclear envelope, contain a substance similar to that of the perinuclear substance. They are formed near the acrosome and follow an helical pathway at the surface of the nucleus. The pouches could be driven by a nuclear ribbon made of six to seven microtubules engaged in the mouth of each pouch. The perinuclear substance, transported by the pouches, is deposited near the posterior part of the nucleus. The evolution of the nuclear pores, and the attachment of the chromatin to the nuclear envelope suggest that the chromatin is twisted inside the nucleus, following the displacement of the nuclear pouches. Adjacent pouches are separated by a lamellar plate, possibly originating from a modified mitochondrion. Untwisting of the nucleus and chromatin is evident at the time the manchette is present. The chromatin fibers become coarser and are progressively aligned parallel to the nuclear axis. The midpiece of the flagellum is very short; it wears 15 mitochondria disposed into three crowns. The ribs of the fibrous sheet are synthesized from the posterior part of the flagellum, anteriorly. A tegosomial sheet is described. It is composed of lipidic droplets that are injected between the two nuclear membranes, prior to the spermiation. A classification of the steps of spermiogenesis is proposed.