The heterocellular female gonad of Rhabdocoela consists of germaria and vitellaria both enveloped by a tunica comprising of an outer extracellular lamina and an inner cellular sheath of accessory cells. In the germaria oocyte maturation occurs completaly during the prophase of the first meiotic division. The main feature of oocyte differentiation is the development of RER profiles and Golgi complexes involved in the production of small inclusions that become localized in the cortical cytoplasm of mature oocytes. In Kalyptorhynchia, Typhioplanida and Dalyelliida the peripheral egg inclusions contain polyphenols and have been interpretated as residual eggshell granules. By contrast the oocytes of Temnocephalida possess peripheral inclusions containing glycoproteins and devoid of polyphenols and have been interpreted as cortical granules. In addition, the scutariellid Troglocaridicola sp. shows proteinaceous acorn-shaped granules which remain scattered in the ooplasm throughout oogenesis and have been interpreted as residual yolk. The maturation process of vitellocytes shows similar ultrastructural features in all the taxa of rhabdocoels examined and is typical of secretary cell producing membrane-bound inclusions: eggshell globules and yolk globules. Eggshell globules contain polyphenols and show a multigranular/ mosaic like pattern. The exception is represented by the scutariellid Troglocaridicola sp. where the poliphenolic eggshell globules show a meandering/ ring shaped pattern similar to that observed in Proseriata and Tricladida. Mature vitellocytes contain, in addition, glycogenand lipids as further reserve material. The phylogenetic significance of some ultrastructural features of oocytes and vitellocytes are discussed.
|Autori interni:||FALLENI, ALESSANDRA|
|Autori:||FALLENI A; LUCCHESI P; GHEZZANI C|
|Titolo:||COMPARATIVE ULTRASTRUCTURAL ASPECTS OF THE FEMALE GONAD IN RHABDOCOELA (PLATYHELMINTHES) AND IMPLICATIONS FOR PLATYHELMINTH PHYLOGENY|
|Anno del prodotto:||2005|
|Appare nelle tipologie:||1.1 Articolo in rivista|