The adult ovary was examined in a freshwater crayfish, Procambarus clarkii, to clarify the ovarian structure and the mode of oogenesis. A Y-shaped ovary consisting of a pair of anterior ovarian sacs and a single posterior ovarian sac was located in the cephalothorax, on the dorsal side of the stomach. An oviduct connected each of the posterior ends of the paired anterior ovarian sacs with the genital pore on the coxa of the 6th appendage. The wall of the ovarian sacs, consisting of a layer of the ovarian epithelium, folded inwards to form a number of oogenetic pouches of various sizes. Each oogenetic pouch contained one egg or large oocyte, vitellogenic or previtellogenic, sometimes followed by a few early previtellogenic oocytes in the oogenetic pouch lumen. Germaria containing oogonia, very early previtellogenic oocytes and somatic interstitial cells were located in the ovarian epithelium near the bases of the oogenetic pouches. In a cross-section of the ovarian sac, the germaria were concentrated in the center of the ovarian sac as a central germarial cluster. An early previtellogenic oocyte beginning to grow left its germarium and raised the ovarian epithelium to form a new oogenetic pouch, in which it remained until mature. Mature eggs were ovulated from the oogenetic pouches into the central ovarian lumen, transferred into the oviducts, and oviposited through the genital pores. The female reproductive system was surrounded wholly and tightly by a thin muscular sheath, which has often been mistaken as the ovarian epithelium in some decapod crustaceans.
Structure of the adult ovary and oogenetic mode were examined in the freshwater crab Potamon dehaani. An H-shaped ovary consisting of a pair of long ovarian sacs connected by a narrow bridge tube is located in the cephalothorax on the dorsal side of the stomach. A short oviduct with a seminal receptacle is connected with the posterior end of each ovarian sac, and a genital pore opens on the sternum of the sixth thoracic segment. The ovarian wall consists of a layer of ovarian epithelium that infolds to form a number of oogenetic pouches of various sizes. These are present mainly in the anterior regions of the ovarian sacs, are scarce in the posterior regions of the ovarian sacs, and are absent from the bridge tube. Each oogenetic pouch contains an egg or a relative large oocyte in its lumen. Germaria containing oogonia, very early previtellogenic oocytes, and somatic interstitial cells are located in the ovarian epithelium near the necks of the oogenetic pouches in the anterior regions of the ovarian sacs and are randomly scattered throughout the ovarian epithelium in the posterior regions of the ovarian sacs. In cross section, the germaria appear to be concentrated into a central germarial cluster in the ovarian sac. In the posterior regions of the ovarian sacs, however, the germaria are randomly scattered throughout the ovarian epithelium. An early previtellogenic oocyte leaves its germarium and raises the ovarian epithelium infolds to form a new oogenetic pouch in which it grows to maturity. Mature eggs are ovulated from the oogenetic pouches into the ovarian lumen, transferred from the ovarian lumen into the oviducts, fertilized there by sperm stored in the seminal receptacles, and then oviposited through the genital pores. The female reproductive system is surrounded wholly and tightly by a thin, cellular, membranous sheath, which has often been mistaken as the ovarian epithelium in some decapod crustaceans.
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