Oogenesis in Kalotermes flavicollis (Fabr.) (Isoptera: Kalotermitidae). I. Differentiation and maturation of oocytes in female supplementary reproductives.

The ovary of female supplementary reproductives is constituted by panoistic-type ovarioles containing a linear array of germ cells in successive stages of differentiation. In the distal region of the germarium, germ cells cannot be morphologically and ultrastructurally discriminated from somatic cells. In the middle and proximal region of the germarium, oogonia at two developmental stages have been identified. The oocytes at the beginning of meiosis are characterized by nuclear vacuoles and by a polar localization of cell organelles, in addition to synaptonemal complexes. The post-pachytene oocytes are partially isolated by prefollicular cell extensions and show annulate lamellae and Balbiani bodies. During previtellogenesis, the oolemma forms microvilli, with coated pits and vesicles, about 60 nm in diameter, at their bases. At the onset of vitellogenesis, coated pits and vesicles about 120 nm in diameter and early yolk globules appear in the cortical ooplasm. At a later stage, wide spaces filled with flocculent material are formed between the oocyte and follicular cells, and coated pits and vesicles about 180 nm in diameter are found in the cortical ooplasm. In late vitellogenesis, the endocytotic activity decreases, and large yolk globules and lipid droplets fill the whole ooplasm. The ultrastructural features during differentiation provide evidence of organelle renewal before vitellogenesis and then exogenous yolk synthesis.