Observations and measurements of sea urchin eggs with a centrifuge microscope

✍ Scribed by Y. Hiramoto

• Book ID: 102881828
• Publisher: John Wiley and Sons
• Year: 1967
• Tongue: English
• Weight: 913 KB
• Volume: 69
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1040690212

✦ Synopsis

Eggs of the sea urchins, Arbacia punctulata and Lytechinus vaAgatus were observed with a centrifuge microscope. The protoplasmic viscosity calculated from the displacement velocity of the nucleus in a centrifugal field is about 30 poises.

The surface forces of the unfertilized egg, which were determined from the relationship between the deformations of the egg in centrifugal fields and the magnitudes of the centrifugal forces, are 0.046 dyne/cm in Arbacia and 0.087 dyne/cm in Lytechinus (mean values). Both of these values increase as the deformation of the egg increases.

The cleavage plane of the first cleavage of the egg in the centrifugal field (35-140 X g ) is parallel to the direction of the centrifugal force. The flattening of the fertilized egg in a constant centrifugal field changes during development, probably owing to the change in the surface force. The flattening attains a minimum shortly before the onset of cleavage and another minimum during the cleavage, corresponding to a peak of the surface force before the cleavage and another peak during the cleavage.