FRANCIS LEROY & GUILLAUME WILMOTTE, BIOCOSMOS / SCIENCE PHOTO LIBRARY FRANCIS LEROY & GUILLAUME WILMOTTE, BIOCOSMOS / SCIENCE PHOTO LIBRARY
Sea urchin fertilisation. Animation showing a sea urchin sperm penetrating an egg. When the sperm comes in contact with the egg it releases enzymes (black dots) from its acroscome (yellow) that digest the jelly coat (grey) of the egg. Next an acrosomal process forms and actin filaments (black line) fuse with the vitelline layer (thick black line) that lays over the egg cell membrane (white). The acromosomial membrane and the egg membrane then fuse and the sperm's nucleus is able to enter the egg.
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