Ultrastructure and histochemistry of the periplasm in oocytes of sturgeons during egg envelope formation.

In the cytoplasm of oocytes (ooplasm) located in ovarian follicles with diameters 2000 microm and 2150 microm in Acipenser gueldenstaedtii, and 2000 microm and 2350 microm in A. baerii, periplasm containing a basophilic compartment and endoplasm containing reserve materials was formed. Vesicles involved in polyspermy blocking and in the formation of the embryo were located in the periplasm. These included compact (cCGs), low-electron-dense cortical granules (lCGs), and lamellar bodies. The cCGs were bounded by a membrane, comprised fibrillar material, fibrils and rod-shaped components. The lCGs were membrane-bounded and contained fibrillar material and granular inclusions. Endoplasmic reticulum (ER) and Golgi complexes were involved in the formation of cCG and lCG. The basophilic compartment, ER and Golgi vesicles participated in the formation of lamellar bodies. They comprised numerous membranes and fibrillar material. It is assumed that they transfer membranes and their precursors to the growing furrow during cleavage and release their content to organize the extracellular matrix. The location of compounds in the developing egg envelope of A. gueldenstaedtii was presented and discussed. Ovaries of both investigated species represented the first pubertal stages of development. Such fish should not be used for reproduction.