This activity is not designed to duplicate those efforts but rather to complement and enhance them. The purpose of this activity is twofold. First, rather than developing or redesigning an activity to add to an already impressive collection of urchin and zebrafish labs, the intent of this activity is to provide teachers with the information they need to obtain and perform one of the numerous preexisting developmental labs on urchins and zebrafish. After completion of a lab on each animal, the second purpose of this activity is to then have students examine the similarities and differences in development between a representative invertebrate and vertebrate animal. The sea urchin development lab has been the classic method of embryological study used for many years by numerous high school and university teachers nationwide.
Urchins have many positive attributes for study in the school setting.
They can be collected at no cost by teachers living close to the ocean or purchased from a biological supply house by teachers who do not have access to saltwater. Once collected, they can easily be induced to spawn and will shed millions of gametes. Students view the sperm and eggs separately and then mix the gametes and observe the moment of fertilization and formation of the fertilization membrane to prevent polyspermy. Development of the fertilized urchin egg is rapid and dramatic with the first division occurring within two hours of fertilization. The embryonic blastula hatches in just over 24 hours and the pluteus larvae can be observed within 72 hours of fertilization.