Normal embryogenesis in Arbacia.

Arbacia, sea urchins, are used by biologists to study embryonic development. The purpose of this experiment was to observe normal embryonic development of the sea urchin, Arbacia. Before the actual fertilization and zygote formation of the sea urchin five steps are performed. The sperm moves toward the egg by chemotaxis, which is movement by the sperm cell in reaction to chemical signals, sent out by the egg cell. The second, third and fourth steps of this process, respectively, are the acrosomal reaction, the sperm cell and egg cell adhesion through the vitelline envelope, and the actual membrane contact between the two cells. The gamete fusion is the last step of this process. The fusion allows the egg to be activated and subsequent embryonic development to occur.

Katie Hopkins, Susan Roy
Department of Biology
Presbyterian College