The cortical contraction related to the ooplasmic segregation inCiona intestinalis eggs

  • Tomo-o Sawada
  • Kenzi Osanai
Article

Summary

The egg cytoplasm of ascidian,Ciona intestinalis, segregates towards both the animal and vegetal poles within a few minutes of fertilization or parthenogetic activation with ionophore A23187. A constriction appears first on the egg surface near the animal pole and then moves to the vegetal pole. Carmine granules and spermatozoa attached to the egg surface move towards the vegetal pole with the movement of the constriction. Microvilli, which are distributed uniformly in unfertilized egg, disappear on the animal side of the constriction and became more dense on the vegetal side of the constriction. Transmission electron microscopy revealed that sub-cortical cytoplasm, containing numerous mitochondria and sub-cortical granules, moves towards the vegetal pole with the movement of the constriction and then concentrates into a cytoplasmic cap at the vegetal pole. An electron-dense layer appears in the cortex of the cap. The ooplasmic segregation and the cortical contraction were inhibited by cytochalasin B and induced by ionophore A23187. These observations suggest that ooplasmic segregation is caused by the cortical contraction which is characterised by a surface constriction and by the formation of an electron-dense layer.

Key words

Ascidian egg Ooplasmic segregation Cortical contraction 

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References

  1. Burgess DR, Schroeder TE (1977) Polarized bundles of actin filaments within microvilli of fertilized sea urchin egg. J Cell Biol 74:1032–1037Google Scholar
  2. Conklin EG (1905) The organization and cell-lineage the ascidian egg. J Acad Natl Sci Philadelphia 13:1–119Google Scholar
  3. Gingell D (1970) Contractile responses at the surface of an amphibian egg. J Embryol Exp Morphol 23:583–609Google Scholar
  4. Hara K (1971) Cinematographic observation of “surface contraction waves” (SCW) during the early cleavage of axolotl eggs. Wilhelm Roux's Archives 167:183–186Google Scholar
  5. Hoshino Z, Tokioka T (1967) An unusually robustCiona from the Northestern coast of Honshu Island, Japan. Publ Seto Mar Biol Lab 15:275–290Google Scholar
  6. Mancuso V (1964) The distribution of the ooplasmic components in the unfertilized, fertilized and 16-cell stage egg ofCiona intestinalis. Acta Embryol Morphol Exp 7:71–82Google Scholar
  7. Ortolani G (1955) I movementi corticali dell'uovo di Ascidie alla fecondaziona. Riv Biol 47:169–177Google Scholar
  8. Reverberi G (1961) The embryology of Ascidians. Adv Morphog 1:55–101Google Scholar
  9. Reverberi G (1971) Ascidians. In: Reverberi G (ed) Experimental embryology of marine and fresh-water invertebrates. North-Holland, Amsterdam, pp 507–550Google Scholar
  10. Reverberi G (1975) On some effects of cytochalasin B on the eggs and tadpoles of the ascidians. Acta Embryol Exp 2:137–158Google Scholar
  11. Schmidt BA, Kelly PT, May MC, Davis SE, Conrad GW (1980) Characterization of actin from fertilized eggs ofIlyanassa obsoleta during polar lobe formation and cytokinesis. Dev Biol 76:126–140Google Scholar
  12. Schroeder TE (1974) Ionophore, calcium and contractility in frog eggs. Exp Cell Res 83:139–142Google Scholar
  13. Schroeder TE (1975) Dynamics of the contractile ring. In: Inoue S, Stephens RE (ed) Molecules and cell movement. Raven Press, New York, pp 305–334Google Scholar
  14. Wessells NK, Spooner BS, Ash JF, Bradley MO, Luduena MA, Taylor EL, Wrenn JT, Yamada KM (1971) Microfilaments in cellular and developmental processes. Science 171:135–143Google Scholar
  15. Zalokar M (1974) Effect of colchicine and cytochalasin B on ooplasmic segregation of ascidian eggs. Wilhelm Roux's Archives 175:243–248Google Scholar

Copyright information

© Springer-Verlag 1981

Authors and Affiliations

  • Tomo-o Sawada
    • 1
  • Kenzi Osanai
    • 1
  1. 1.Marine Biological StationTohoku UniversityAsamushi, AomoriJapan

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