ULTRASTRUCTURAL CHANGES OF THE OOGENESIS IN THE POLYCHAETE Capitella capitata (Fabricius)

The ultrastructural changes of the oogenesis in Capitella capitata are described. The developing oocytes undergo obvious ultrastructural changes during the process of oogenesis, which include:the formation or differentiation of endoplasmic reticulum, Golgi complex, endocytotic pits, vesicles and the surface of the cell. The evidence demonstrates that these changes are connected with the process of yolk synthesis which occures largely within the ovary by means of autosynthesis and heterosynthesis. The results show that the Golgi complex and the endoplasmic reticulum within both the oocytes and the follicle cells are involved in the yolk synthesis and transformation of probable yolk precursors. In summary, the similarities of oogenesis in the sibling species of Capitella suggest that there is a very close evolutionary relationship between them.