Ultrastructural Observations on Sperm Penetration in the Egg of Elkhorn Sculpin, Alcichthys alcicornis, Showing Internal Gametic Association

概要

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Early fertilization process has been investigated ultrastructurally in elkhorn sculpin, Alcichthys alcicornis. In the eggs before immersion in sea water, spermatozoon was seen to be attached to the ooplasmic membrane at the site of an inner opening of the micropylar canal. By 10 sec after immersion in sea water, a fertilizing spermatozoon penetrated the ooplasm for about half the head length, and vesiculation occurred on the fused plasma membrane at the apical region of sperm head. By 30 sec after the immersion , the fertilizing spermatozoon showed a change in the tail axoneme , indicating a loss of its motility. By 1-2 min after the immersion, spermatozoon further penetrated the ooplasm up to its middle piece. It is worthy to note that a portion of ooplasm containing no significant cytoplasmic organelles other than ribosomes appeared around the penetrated sperm head and came to expand during the sperm penetration to form a triangular region surrounding the sperm head. This ooplasmic region may have a role in an active engulfment of immotile spermatozoon into the ooplasm. By 3 min after the immersion, sperm nuclear membrane was separated from chromatin and became vesiculated starting from the anterior region of sperm head caudalwards. Details of the events in early fertilization process were presented.
社団法人日本動物学会の論文
1993-02-15