title: Ultrastructural studies on oogenesis in Symphyla: previtellogenic and vitellogenic stages.
abstract: The paired ovaries of Symphyla are sac-shaped. Their interior is filled with synchronously developing oocytes surrounded by a simple follicular epithelium. Previtellogenic oocytes have spherical or oval nuclei, the latter containing a large number of small nucleoli. Part of the nuclear surface is covered by a thick "coat" made up of a granular substance of medium electron density. The "coat" is penetrated by cisternae of the smooth endoplasmic reticulum. Micropinocytosis is the principal source of yolk in Symphyla;a small amount of yolk material arises within the mitochondrial cristae. Vitellogenic oocytes are characterized by a highly active rough endoplasmic reticulum synthesizing a material, probably lipoprotein in nature, which is incorporated into lipid droplets.
mesh_terms: D000818:Animals; D001181:Arthropods / Q000648:ultrastructure*; D002467:Cell Nucleus / Q000648:ultrastructure; D003593:Cytoplasm / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D005260:Female; D008854:Microscopy, Electron; D009865:Oocytes / Q000648:ultrastructure*; D009866:Oogenesis; D006080:Ovarian Follicle / Q000648:ultrastructure; D010063:Ovum / Q000648:ultrastructure*