Animal, Algae or Rock? Cells in the Zoo Coral Nursery

Behind the Glass at the Coral Nursery

1The aquarium building at Bayview Zoo has a coral nursery. It is part of a conservation program that grows corals for reef research. Staff cut small fragments from healthy corals, glue each one to a ceramic plug and raise them in tanks of warm, lit seawater. The program hopes to return some of these corals to damaged reefs one day. This year, sixth grader Jonah Abernathy joined the nursery as a teen volunteer.

2Aquarist Dr. Malia Kekona explained that each fragment is a colony of tiny polyps. A polyp has a soft body with a ring of tentacles around its mouth. Each evening the polyps open their tentacles to catch the tiny living food the staff add to the water. The polyps sit on a hard, white skeleton that they lay down beneath themselves, a little more each month, from minerals in the seawater.

3Dr. Kekona let Jonah look at samples under the lab microscope at 400×. He recorded what he saw in the log below. She also showed him a dish of lit seawater in which golden-brown cells taken from a coral had been kept for a month with no coral in it. The cells had kept dividing until they formed a brownish film. The same kind of golden-brown cell is also found living freely in the water over reefs.

4Inside a healthy coral, millions of these golden-brown cells live within the cells that line the polyps' gut. They give the coral most of its color, and they use light to make food, some of which they share with the polyps.