Mount Holyoke College

Sea Urchin Embryos:
A vegetal view of the developing gut


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This time-lapse video was made by Munira Bhaidani and Kiyoko Takahashi (Bio 305, fall 99). As a sea urchin embryo develops, it forms a spherical blastula. One side of this is called the vegetal plate. At the beginning of gastrulation, as the embryo is making a gut, this vegetal plate buckles in in a process called invagination. Munira and Kiyoka filmed a vegetal-pole view of a gastrulating embryo. The large ring in the center is the primary invagination of the developing gut. Over the course of 45 minutes of real time (compressed by time-lapse into a few seconds) you can see this ring get narrower and tighter, reflecting the cellular rearrangements that are occuring in the elongating gut. Eventually this invagination will form a tube with a mouth at one end, and the anus at the other (this is not shown in this movie). The individual cells outside the gut are primary mesenchyme cells, which make the larval skeleton.