Jelly Coat On Eggs
Sea urchin eggs have a "jelly" coat around them that serves them in many ways.
- It prevents too many sperm from getting to the egg at the same time, because of its viscosity.
- Proteins in the jelly initiate the acrosome reaction in sperm so they are ready to fertilize the egg.
- It provides a sort of "shock absorber" to prevent injury to the egg from wave action.
It is colorless, so it is difficult to see.
- Add a small amount of "sumi ink" to the sea water surrounding the eggs to make the jelly layer more visible.
- The ink particles are too big to get through the jelly layer and are excluded.
- Where the ink is excluded, more light can get through and we see the jelly layer as a clearing around the eggs.