La vitellogenese chez Patella coeruelae LMK (Mollusca, Gasteropoda). Approche ultrastructurale

During the reproductive period, the microscopical observation of Patella coerulea ovary shows some ovogonies forming neets, supported by a conjonctive network, previtellogenic oocytes which leave gradually the conjonctive tissue and vitellogenic oocytes isolated in the acinus lumen. In early stages of previtellogenesis, an important nucleolar activity, caracterised by cloud-shaped or nematosomes and ribonucleoproteinic extrusions in cytoplasm compartment can be observed. At the end of this stage, the oocyte becomes richer in organites, mitochondria, granular endoplasmic reticulum and Golgi. We further notice the outcome of the first vitellin platelets. Production of vitellus is higher as three kinds of vitellus are observed in the following order: dark lipidic vitellus which seems to be a consequence of mitochondrial transformation, light proteinic vitellus, always associated with ergastoplasmic structure and annulated lamellae, cortical granule, which contain peripherical fibrous material of mucopolysaccharide nature.