Oogenesis in supplementary reproductives of Reticulitermes lucifugus Rossi(Isoptera, Rhinotermitidae): an ultrastructural study

The Reticulitermes lucifugus ovary consists of about 40 panoistic ovarioles . A transverse septum between the terminal filament and germarium is absent , where two successive developmental stages of oogonia are recognizable. Ea rly meiotic oocytes with synaptonemal complexes and nuclear vacuoles charac terize the prophase region. Previtellogenic oocytes first show microvilli a nd later, in the cortical ooplasm, endocytotic vesicles about 70 nm in diam eter. Small yolk spheres and 120 nm coated vesicles characterize early vite llogenic oocytes, while 180 nm vesicles prevail in mid- and late vitellogen esis. The observations support heterosynthetic yolk production and endocyto sis of yolk precursors. Prefollicular cells surrounding oogonia and early m eiotic oocytes have a scarcely differentiated cytoplasm. Around early previ tellogenic oocytes, follicular cells build a monolayered epithelium, first flat then cuboidal and release a granular material on the oocyte side. They closely adhere to each other and extend microvilli interdigitating with th ose of the oocyte. During vitellogenesis they are first columnar then globo se and show large intercellular spaces which disappear in the final stage o f vitellogenesis when they again become flat. Follicular cells apparently r egulate transfer of materials for oocyte growth and after vitellogenesis sy nthesize egg envelope precursors. During choriogenesis they show an extende d proteosynthetic apparatus whose products are exocytosed on the egg-facing surface and, after choriogenesis, produce a finely granular matrix coverin g the egg, easing oviduct transit and binding together newly laid eggs. The postovulatory follicle becomes the "corpus luteum" composed of degeneratin g, non-steroidogenic cells.