Secretory product of the lateral oviducts of Baculum thaii haus. (Phasmida: Phasmatidae) and its change during egg transit

The secretory product elaborated by the epithelium of the lateral oviducts of Baculum thaii (Phasmida: Phasmatidae) gives rise, in the oviduct lumen, to 2 main structural types: fibrils and granules. The ultrastructural characteristics of the fibrils are uniform throughout the various oviductal zones in both the virgin and mated females. However, the organization of the granules is characteristic of a particular zone, and sometimes different in the same zone, when virgins are compared with mated females. The fibrils accumulate on the chorion of newly ovulated eggs to form a thick, compact sheath outside which the granules converge, undergo rapid and multiple fragmentation, and overlay the fibrillar sheath in an orderly arrangement. The fibrillar and granular components give rise, in both virgin and mated females, to the formation of a sclerotized sheath called extrachorion that is still present in newly laid eggs. The probable role played by these 2 extrachorionic components in relation to the egg is discussed.