Document Detail

Fertilization in a chiton: acrosome-mediated sperm-egg fusion.
MedLine Citation:
PMID:  3246365     Owner:  NLM     Status:  MEDLINE    
Contrary to the widely accepted view that chiton sperm lack acrosomes and that fertilization in this group occurs via a micropyle, we demonstrate here that fertilization in Tonicella lineata occurs by acrosome-mediated sperm-egg fusion. The acrosome is a small vesicle containing two granules located at the tip of the sperm. The eggs have an elaborate hull (= chorion), which is formed into cupules that remain covered by follicle cells until maturity. When dissected ripe eggs were exposed to sperm in vitro, the sperm were attracted only to open cupules, inside which they swam through one of seven channels to the base where they penetrated the hull. The acrosome fired on contact with, or in, the hull, and during passage through it the apical granule was exhausted while the basal granule was exposed. If sperm contacted follicle cells between the cupules the acrosome did not react. The vitelline layer beneath the hull contains pores arranged in a regular pattern. Embedded in the base of each pore is an egg microvillus. Having penetrated the hull the sperm anterior filament located a pore and fused with the tip of the egg microvillus projecting into it. This created a membranous tube, through which the sperm nucleus was injected into the egg. The egg membrane appeared to be raised up into a small fertilization cone around the penetrating sperm, the vitelline layer became slightly elevated, and some cortical granules were released by exocytosis.
J Buckland-Nicks; R Koss; F S Chia
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Gamete research     Volume:  21     ISSN:  0148-7280     ISO Abbreviation:  Gamete Res     Publication Date:  1988 Nov 
Date Detail:
Created Date:  1989-06-16     Completed Date:  1989-06-16     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7806559     Medline TA:  Gamete Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  199-212     Citation Subset:  IM    
Department of Zoology, University of Alberta, Edmonton, Canada.
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MeSH Terms
Acrosome / enzymology,  physiology,  ultrastructure
Microvilli / physiology
Models, Anatomic
Mollusca / physiology*
Organelles / physiology
Ovum / ultrastructure
Sperm-Ovum Interactions
Spermatozoa / ultrastructure

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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