Ovogenèse et transmission des bactéries symbiotiques chez le charançon Sitophilus oryzae L. (Coleoptera: Curculionoidea)Summary. Oogenesis and transmission of symbiotic bacteria in the weevil Sitophilus oryzae L. (Coleoptera: Dryophthoridae). Among Coleoptera, and particularly in numerous Dryophthoridae, the insects share intracellular symbiosis with hereditary Gram-negative bacteria (or endocytobiotes). Sitophilus oryzae Primary Endosymbiote (SOPE) belongs to the γ3-proteobacteria group. It is a pleomorphic rod shaped (1 to 30 µm ), non-sporulating and non-ciliated bacterium. In the bacteriocyte the bacteria are not included in vacuoles but lie freely in the cytoplasm. SOPE is closely related to Escherichia coli, with 95% homology on the 16S rDNA gene, and also the primary endosymbiotes of Sitophilus zeamais (97,8% identity). In addition to SOPE, several wild strains of S. oryzae harbor a second symbiotic bacterium, that belongs to the B-group of Wolbachia (an α-proteobacterium). They are not considered in this work since studied strains were deprived of Wolbachia. Previous studies have shown that SOPE is transmitted to the offspring strictly through the female. The bacteria are located in ovaries and in the larval bacteriome. The latter organ is at the junction stomodeummidgut, and does not communicate with the gut lumen. It is dissociated at metamorphosis. This work aims to better describe oogenesis in the weevil Sitophilus oryzae and some other Coleoptera. It was performed with various techniques, some of them being original in histology and histochemistry (BMN fixative, RPH and RPMy). Autoradiographic studies were used to precise the nucleic acid (DNA, RNA) and protein metabolism, in the different cell types of the ovary, and in the symbiotic bacteria. In the adult females, the ovarioles are surrounded with a Tunica propria and a double sheath of flat cells, which present a ribonucleo-proteic metabolism. In the apical bacteriome the bacteriocytes are giant polyploid cells. They contain numerous symbiotic bacteria and exhibit a low cellular activity although they do multiply. They also show a lytic activity with myelinic degeneration figures. Between the bacteriocytes small interstitial cells can be seen. These small cells are also visible between the trophocytes in the tropharium. The trophocytes, or nurse cells, are polyploid and form a pseudosyncitium like. They harbor numerous symbiotes and mitochondria. The chromosoma are apparently at the end of pachytene or at diplotene stages. In opposition to most other telotrophic insects, the nutritive cords are poorly developped in S. oryzae. Despite an intense metabolism of RNA and proteins, no transfer of these substances to oocytes was seen. The oogenesis is accomplished in 8 serial steps, with the two first stages occurring in the nymph. The stage 1 includes oogonia and the stage 2 begins at the first step of meiosis and ends at pachytene. SOPE are rarely visible. At the stage 3 oocytes are found among the prefollicular tissue, at the basis of tropharium (3A)...