EDUCATION: When Gametes Collide

Science  03 May 2002:
Vol. 296, Issue 5569, pp. 811d
DOI: 10.1126/science.296.5569.811d

Spiky and rotund, an adult sea urchin looks more like a big, wet cocklebur than one of our close kin. Yet the early stages of development are very similar in humans and urchins, which makes these marine echinoderms excellent subjects for labs on embryology.

High school or college teachers who want to induct urchins into their courses can get plenty of wise guidance from this tutorial and lab manual hosted by Stanford University's Hopkins Marine Station. Started 5 years ago, the how-to explains the procedures for staging and observing sea urchin fertilization and early development. It describes, for example, how to stimulate the discharge of sperm and eggs with injections of potassium chloride, and how to house and feed the animals (if you can't obtain seaweed, they relish “urchin cookies” made from eggs, carrots, seawater, and agar). Projects include cookbook procedures and student-designed explorations, and seasoned teachers will appreciate this potential lifesaver: alternative experiments in case your best laid plans go awry. Adding pizzazz are animations that illustrate hard-to-visualize events, such as a sperm ramming through the gelatinous layer shielding the egg like an icebreaker plowing through frozen Arctic seas.

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