A light- and electron-microscopic investigation of gametogenesis in Typosyllis pulchra (Berkeley and Berkeley) (Polychaeta: Syllidae)

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Abstract
Oogenesis in Typosyllis pulchra begins with a short proliferative gonial phase. Gonial clusters, consisting of six to eight syncytial sibling cells, are surrounded by gonial peritoneum and are eventually liberated into the coelom. At about the same time as the onset of the coelomic phase, one gonial cell in each cluster differentiates, begins to accumulate yolk and increases in size, eventually to become a mature oocyte. Yolk is composed of lipid droplets and membranebound protein granules. The protein component appears to be at least partially synthesized by the oocyte although there are some signs of endocytosis. Nurse cells and peritoneal cells are apparently able to manufacture some protein that may also be utilized by the oocyte. The nurse cells maintain cytoplasmic continuity with the oocyte, and mitochondria and ribosomes are often seen within the intercellular bridges between oocyte and nurse cell. Immediately prior to spawning, oocytes undergo prematuration and cytoplasmic reorganization. Ultrastructural changes which occur during oocyte growth and maturation are described.