Vitellin accumulation and vitellogenin synthesis in relation to oogenesis inPennereis Cultrifera(Polychaeta Annelida)

Summary The accumulation of total protein and exogenously synthesized vitellin has been quantified during oogenesis of P. cultrifera. The bulk of protein accumulation occurs during the second stage of oogenesis, i.e., in the period of pronounced oocyte growth or corticogenesis which follows the so-called vitellogenesis stage. However, although cortical alveolus protein (two major polypeptides of 24,000 arid 18,000) comprises a significant proportion of the total protein at maturity, the massive increase in protein content in cortical alveolus stage oocytes appears to be due mainly to vitellin accumulation which continues throughout oogenesis. In addition, the results of in vitro metabolic studies show a progressive increase in the rate of secretion of newly synthesized vitellogenin by the coelomocytes (eleocytes) which produce this protein until the completion of oocyte growth. Thus, in contrast to the results from previous cytological and autoradiographic studies, the present data clearly indicate that the vitellogenesis process is active not only during the “vitellogenic stage” but also throughout corticogenesis and demonstrate that the bulk of the main yolk protein is synthesized and accumulated during the second stage of oogenesis.