Ultrastructure of germaria and vitellaria in Dugesia sicula Lepori, 1948 (Platyhelminthes, Tricladida, Paludicola)

The female gonad of the diploid and sexual planarian Dugesia sicula Lepori, 1948 has been studied by means of transmission electron microscopy (TEM). The germaria consist of two ovaries occurring in the anterior body part behind the eyes. The vitellaria are composed of two lateral rows of vitelline follicles ranged dorsally and ventrally from the ovaries to the copulatory apparatus. During their growth, oocytes are provided with scattered residual yolk globules. The cytoplasm of maturing oocytes is filled with mitochondria, chromatoid bodies, Golgi complexes, RER, annulate lamellae and small yolk globules (2-3 μm in diameter) surrounded by a simple membrane, and lacks cortical granules. During the early stage of differentiation, vitellocytes enclose well-developed RER and Golgi complexes. Mature vitellocytes show yolk and eggshell globules, lipid droplets and glycogen particles. Golgi complexes and RER are involved in the production of eggshell and yolk globules respectively. Eggshell globules exhibit a concentric pattern typical for triclads.