.
The first experiment, a Calcium ionophore is added which should boost the cortical reaction. .
Cortical Reaction: This process consists of the secretion of cortical granules into the space between the plasma membrane and the zona pellucida. This renders the membrane of the oocyte impermeable for other sperm cells. .
The cortical reaction occurs normally in Ca++- depleted medium, providing evidence that intracellular, not extracellular, Ca++ is important. After the sperm cell has penetrated the oocyte, the cortical reaction takes place. .
In the second experiment, EDTA was added which should prevent the cortical reaction. Hence little or no fertilization should occur.
The control experiment will be natural. With no solution added to it. So there should be fertilization. .
Materials.
Male and Female Sea Urchins.
Hypodermic Needle.
Seawater.
Depression Slides and Cover Slips.
Petri Dishes Pipettes.
Microscope.
Calcium Ionophore.
EDTA Solution.
Potassium Chloride (KCl) .
Method .
Control Experiment.
Inject the sea urchins in the oral region with 0.5 M of KCl to induce spawning of the resulting sperm and eggs. .
If the gametes are white or creamy, the urchin is a male, if the gametes are orange the urchin is a female.
Place the male sea urchins on a dry petri dish and the female sea urchin, place it on a beaker filled with seawater.
Using a pipette remove some of the eggs and place them on the slide and add to it a drop of equal size of seawater put a cover slip (don't press down) and observe.
Carefully add the sperm and study the normal fertilization of eggs observing what happens to the oocytes as the sperm come close and touch them.
Make drawings of what is seen.
Experiment # 1.
Add a drop of egg solution on the slide and a drop of EDTA solution. Put a cover slip and observe. .
Add the sperm and observe.
Make drawings of what is seen.
