Ultrastructural Study of the Female Reproductive System of Saduria Entomon (Linnaeus, 1758) (Isopoda, Valvifera)

Abstract

[The structure of the ovaries, oviducts, fertilization chamber and spermathecae of a mature female of Saduria entomon (L., 1758) is presented at the ultrastructural level. In the ovaries a proximal and a distal part is distinguished. The proximal part is only built of a flattened epithelium lying on a thick basal lamina. In the lumen of this part are previtellogenic and primary vitellogenic oocytes enveloped in follicle cells in which synthetic organelles are absent. Previtellogenic oocytes have large nuclei containing synaptonemal complexes and very large nucleoli with vacuoles of various sizes. Primary vitellogenic oocytes are characterized by intra-oocytic yolk formation inside the elements of the endoplasmic reticulum. The walls of the distal parts of the ovaries and oviducts are built of an epithelium and its surrounding muscle cells. On the lumen side, the oviduct epithelium is covered with a cuticle in which an epicuticle and an endocuticle can be distinguished. The fertilization chamber is built of large cells containing bundles of myofilaments in some areas. Their cytoplasm is rich in mitochondria and glycogen granules. The bundles of myofilaments occurring in the muscle cells of the ovaries, oviducts and the cells of the fertilization chamber are striated. They are characterized by a short sarcomer length (2.6 μm and 3.5 μm) and a high ratio of thin-to-thick filaments. The single epithelium building the spermathecae is separated from the haemocoel only by a basal lamina. The apical surface of the epithelium is covered with a thick intima which does not look like a cuticle., The structure of the ovaries, oviducts, fertilization chamber and spermathecae of a mature female of Saduria entomon (L., 1758) is presented at the ultrastructural level. In the ovaries a proximal and a distal part is distinguished. The proximal part is only built of a flattened epithelium lying on a thick basal lamina. In the lumen of this part are previtellogenic and primary vitellogenic oocytes enveloped in follicle cells in which synthetic organelles are absent. Previtellogenic oocytes have large nuclei containing synaptonemal complexes and very large nucleoli with vacuoles of various sizes. Primary vitellogenic oocytes are characterized by intra-oocytic yolk formation inside the elements of the endoplasmic reticulum. The walls of the distal parts of the ovaries and oviducts are built of an epithelium and its surrounding muscle cells. On the lumen side, the oviduct epithelium is covered with a cuticle in which an epicuticle and an endocuticle can be distinguished. The fertilization chamber is built of large cells containing bundles of myofilaments in some areas. Their cytoplasm is rich in mitochondria and glycogen granules. The bundles of myofilaments occurring in the muscle cells of the ovaries, oviducts and the cells of the fertilization chamber are striated. They are characterized by a short sarcomer length (2.6 μm and 3.5 μm) and a high ratio of thin-to-thick filaments. The single epithelium building the spermathecae is separated from the haemocoel only by a basal lamina. The apical surface of the epithelium is covered with a thick intima which does not look like a cuticle.]