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KMID : 0364219770200020077
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Korean Journal of Zoology
1977 Volume.20 No. 2 p.77 ~ p.92
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Oogenesis in a Tubiculous Polychaete, Schizobranchia insignis Bush: I. Microscopic and Biometric Studies
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Lee Yang-Rim
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Abstract
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A study has been made to correlate morphological and biochemical differentiation in the oocytes of a tubiculous polychaete, Schizobranchia insignis. The pressent paper is concerned with an examination of the cytological changes during oogenesis and annual size distribution of oocytes, The oocytes are released from the ovary into the coelomic sac at the end of the oogonial division and grow to a maximum size (180 $\\mu$ diameter). Oogensis takes place continuously throughout a year, although the breeding season is the period between January and March. When the oocytes reach the largest size class, they remain constant in size thereafter and accumulate in the coelomic sac. The nucleolus, which first appears in the oocytes 5-10$\\mu$ diameter, grows in the early stages of oogenesis, becomes maximum in the oocytes 100-120$\\mu$ diameter, and is constant throughout the rest of the pertiod. The nuclelus initially has a single comartment but becomes bipartite prior to vitello genesis. Three types of yolk including lipid droplets, proteid granules and oval granules oof unknown composition form at different times of oogenesis. The lipid droplets and oval granules appear in the early stage, but mainly in the oocytes larger than 80 $\\mu$ diameter. Proteid yolk and cortical granules appear only in the oocytes larger than 80 $\\mu$ diameter Microvilli are abundant in the oocyte 80 $\\mu$ diameter and embedded in the vitelline membranc. In the oocytes 180 $\\mu$ diameter they have retracted from the vitelline membrane.
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