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Spermiogenesis in Thysaniezia ovilla begins with the appearance of a differentiation zone equipped with peripheral microtubules, surrounded by arched membranes and containing two parallel centrioles surrounded by electron dense granular material. One of the centrioles aborts, the other gives rise to a flagellum which quickly grows in the cytoplasmic(More)
Bundles of microtubular structures appear in the cytoplasm of spermatids of the African frog Dicroglossus occipitalis. They are observed in the vicinity of axonemes. Natural tubulin polymerization leads to the formation of hooks on microtubular structures. They can be related to experimentally induced tubulin hooks. The direction of curvature of the hooks(More)
During meiosis in the male of a cyprinodontid fish, Aphyosemion splendopleure, and during the organization of the spindle of division, the spindle is made of two types of tubules: microtubules (20-25 nm) and macrotubules (30-50 nm). The macrotubules are associated only with the polar region of the meiotic apparatus and are located outside the spindle of(More)
The middle region of the spermatozoon of Hexostoma exhibits two 9 + "1" axonemes, the nucleus, the mitochondrion, and cortical longitudinal microtubules. The ultrastructure is similar to that of other Polyopisthocotylean monogeneans and this confirms the position of the family Hexostomatidae within Polyopisthocotyleans.
In Megalocotyle the zones of differentiation (ZD) are short and incomplete; there is no median cytoplasmic process or free flagella. Some peripheral microtubules are present in early ZD, but they disappear. Each nucleus of the common cytoplasmic mass inserts one extremity into a ZD. The mitochondria fuse around this extremity and form a beadlike perforated(More)
The Centrorhynchus milvus spermatozoon is a filiform cell. The free part of the flagellum measure 2 mu and is situated in front of the gamete. The centriole is no more visible but an axial tubule formation is found at the anterior extremity of the flagellum. This Polymorphidae spermatozoon shows a reversed anatomy like the one we described for the first(More)
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