DEVELOPMENT OF THE NUCLEAR STRUCTURE AND METABOLISM DURING OOGENESIS OFPERINEREIS CULTRIFERA(ANNELIDA, POLYCHAETA)

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Abstract
An ultrastructural study of the nucleus was carried out, during oogenesis of Perinereis cultrifera, accompanied by an autoradiographic and biochemical study of the syntheses of RNA. The nucleus encloses formations deriving from the dispersal of meiotic chromosomes and a voluminous nucleolus. The latter undergoes morphological development of which each stage is characteristic of a stage of oogenesis. The autoradiographic study shows that the synthesis of RNA of extra-nucleolar origin is highly intense in young oocytes (during the stages of previtellogenesis and vitellogenesis) and that it decreases in older oocytes. The synthesis of RNA of nucleolar origin is very weak during previtellogenesis, increases during vitellogenesis, which is the stage at which it reaches its peak, and then decreases during the stages of the development of cortical alveoli and of maturity. These autoradiographic results are confirmed by a biochemical study which shows that once an oocyte diameter of 80 μm is reached (mid-vitellogenesis), the specific radioactivity of 18 and 28 S rRNA and of 4 and 5 S RNA decreases progressively up to the end of oogenesis.