Figure 6

Embryophore ultrastructure before and during the early phase of matrotrophic nutrition in Bicellariella ciliata (TEM). In all images the cuticle of the ooecial vesicle is shown with arrowheads. A, non-hypertrophied epithelial cells of the non-developed embryophore in an empty ovicell; B-D, beginning of embryonic incubation accompanied by hypertrophy of the epithelial cell of the embryophore: B, part of epithelial cell showing developing RER and flocculent material in the brooding cavity (arrow points to a formation of supposedly endocytotic vesicle), C, formation of the first foldings between two epithelial cells (cell borders arrowed, secretory vesicle with flocculent material is seen just beneath this zone), D, hypertrophied epithelial cells showing well-developed RER and zones of foldings (surface of the early embryo with infoldings are seen in the right upper corner). Abbreviations: bc, brooding cavity; co, coelom of ooecial vesicle; e, embryo; eph, epithelial cells of embryophore; fd, foldings of embryophore cells; fm, flocculent material; ga, Goldgi apparatus; mi, mitochondria; ns, nucleolus; nu, nucleus; rer, rough endoplasmatic reticulum; sv, secretory vesicle. Scale bars: A, D, 2.0 μm, B, C, 1.0 μm.