Ultrastructural study of oogenesis in Xiamen amphioxus

Using electron microscopic technique, ultrastructural characters of the oogonia and oocyte at the different phases of amphioxus are observed in detail in the present study. The squeezed out nucleolus, nucleolus-like bodies and yolk nucleus at the side of nucleus are the characters in the early egg cells of the first and secondary phase. The nucleus and cytoplasm of oocyte change obviously their morphology and structure from large growth stage to mature stage (from Stage Ⅲ to Stage Ⅴ).As a result, the dense distribution of nuclear pore and the extension and depression of nuclear envelope are observable. Mitochondria, Golgi complex, rough endoplasm reticular and annulate lamellae, and others in the cytoplasm join in the formation of yolk granular. Their morphology and number also change correspondingly with the development and maturation of the oocyte. These results will provide a whole base for the reproductive physiology and artificial propagation as well as the resource management of amphioxus.