Oogenesis in Kalotermes flavicollis (Fabr.) (Isoptera, Kalotermitidae). II . Prefollicular and follicular cell ultrastructure during oogenesis in female supplementary reproductives.

Ovariole somatic cells were examined by light and electron microscopy. Prefollicular, follicular and interfollicular cells were identified. Prefollicular cells envelop oogonia and oocytes at the beginning of meiosis; they have a scarcely differentiated cytoplasm with protrusions penetrating between germ cells and between these and the tunica propria. Follicular cells form a flattened epithelium around initial previtellogenic oocytes, and during previtellogenic growth they proliferate and change from flattened to cuboidal and then columnar shape. They adhere tightly to each other and apically form microvilli which extensively interlock with oocyte microvilli. During vitellogenesis, the follicular cells show a globose shape; wide intercellular spaces appear between adjacent cells and between follicular cells and the oocyte. Their cytoplasm becomes enriched in rough endoplasmic reticulum cisternae, Golgi complexes, mitochondria and microtubules, particularly near the basal area. At the end of vitellogenesis the follicular cells are flattened and very wide, and earlier intercellular spaces have disappeared. From the last previtellogenic stages to the end of oocyte development, the ovarian follicles are separated by interfollicular cells anchored to the tunica propria and characterized by the present of numerous microtubules in the cytoplasm. The function of the ovariole somatic cells is discussed in relation to the stages of oocyte differentiation and growth.