Histochemical and cytological observations on the developing ovary of Sarcophaga lineatocollis Macq. (Diptera-Muscidae)
Bhide, M.; Sahai, Y.N.
Folia Morphologica 34(2): 187-196
1986
ISSN/ISBN: 0015-5640 PMID: 3744181 Document Number: 274703
A pair of typical muscid ovaries, with 25-30 polytrophic ovarioles, is found in Sarcophaga lineatocollis. Development of the penultimate egg follicle is delayed up to the development of the ultimate (last or distal) follicle and it starts developing after ovulation. Each developing egg follicle contains 15 trophocytes or nurse cells and one oocyte, all produced by four successive mitotic divisions of the oogonium, as in Muscidae in general. The oocyte is soon differentiated from the trophocytes; it also grows faster, while the size of the trophocytes-together with their contents-steadily diminishes. The trophocytes are interconnected by cytoplasmic bridges (fusosomes) and are also connected with the oocyte of the same follicle. The entire egg follicle, i.e. 15 trophocytes + 1 oocyte, is wrapped in follicular epithelium which plays an active role in the transfer of vitellogenin from the haemolymph to the developing oocyte. The follicular epithelium is proteinaceous and its cells contain mitochondria and Golgi bodies. The germinal vesicle is somewhat smaller than the trophocyte nuclei; it has one nucleous, while the trophocyte nuclei contain 7-9 nucleoli. The oocyte nucleus lies close to the nurse cell chamber. Mitochondria and Golgi bodies are found in large numbers round the trophocyte nuclei and near the follicular epithelium, i.e. at the periphery of the ooplasm, showing where protein is presumably synthesized. Conjugated proteins in Sarcophaga take the form of glycoprotein and lipoprotein, present in the ooplasm. After ovulation, yellow-coloured bodies are found at the junction of the ovariole and the pedicle. They are corpora lutea, in which the follicular epithelium is actively degenerating. Folding and refolding of the tunica propria is indicative of active reduction and resorption of the corpus luteum.