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KMID : 0381920000300010061
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Korean Journal of Microscopy
2000 Volume.30 No. 1 p.61 ~ p.72
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Fine Structural Investigations of Fertilization Envelopes and Acrosomal Reaction in Urechis unicinctus
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Kwon Hyuk-Jae
Shin Kil-Sang
Kim Wan-Jong
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Abstract
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Three fertilization envelopes (FE) have been observed after the artificial insemination of U. unicinctus oocytes. The substances of the first fertilization envelope, which is an effective barrier against excessive sperm, come mainly from the surface coat of the oocyte. The secretions of the cortical granules take part in formation of the 2nd fertilization envelope. Histologically, the 3rd fertilization envelope is not amorphous as seen under light microscope, but contains numerous panicles under electron microscope, which would be contributed to harden the envelope by 60 min after the fertilization. With the substantial similarity between the 1st fertilization envelope and the surface coat of the oocyte, and the coincidence of retraction of microvilli and the formation of the 1st fertilization envelope, it is suggested that the microvilli contain the sperm receptors in U. unicinctus. Some granular substances from the distal part of the acrosome diffuse on the surface coat of the oocyte while the acrosomal tubules penetrate into the surface coat. The acrosomal tubules arise from the proximal part of the acrosome and pass through the acrosomal lumen.
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KEYWORD
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Acrosomal tubule, Cortical granule, Fertilization envelope, Ultrasoucture
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