Summary
The egg coats of a starfish (Patiria miniata) are examined before, during, and after the cortical reaction by scanning and transmission electron microscopy. The unfertilized egg is closely invested by a vitelline coat about 300 μm thick, and cortical granules are scattered in the peripheral cytoplasm. After insemination, as the cortical granules undergo exocytosis, the cortical reaction sweeps over the egg surface. Much of the material ejected from the cortical granules adheres to the inner surface of the vitelline coat as a dense layer about 40 μm thick and as scattered spheres and hemispheres, each about 1 μm in diameter. Together, the vitelline coat and the adherent cortical granule material form the fertilization envelope, which becomes separated from the plasma membrane of the egg by a perivitelline space. The perivitelline space contains some flocculent material, which is too diffuse and discontinuous to be considered a hyaline layer. Possible functions of the starfish egg coats are discussed.
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Supported by USPHS Grant No. R-07011 (1979–1980). Ms. Ellen Flentye gave competent assistance with the scanning electron microscope, and the manuscript was criticized by Ms. Linda Holland and Dr. Mia Tegner
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Holland, N.D. Electron microscopic study of the cortical reaction in eggs of the starfish (Patiria miniata). Cell Tissue Res. 205, 67–76 (1980). https://doi.org/10.1007/BF00234443
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DOI: https://doi.org/10.1007/BF00234443