Animal, Vegetable, or Mineral?

by B. N. Sullivan

Take a look at the photos below. What's your guess: animal, vegetable or mineral?

At first glance they look like some kind of vegetable, don't they? Perhaps cauliflower or broccoli come to mind?

In fact, the correct answer is "animal."  The images above are macro photos of a type of soft coral in the genus Dendronephthya.  The common name for this variety is "Broccoli Coral," and you can see why that is so.

Although this kind of coral can resemble broccoli in appearance, it definitely is not a plant.  It is a colony of animals -- the coral polyps. The polyps arrange themselves in bundles at the ends of the rubbery stalks. Each polyp has exactly eight short, feathery tentacles. In order to feed, the polyps open and close their little tentacles, grabbing tiny nutrient particles that are suspended in the water.

This feeding activity happens mostly at night.  During daylight hours, the polyps retract into tiny bundles, as you see in these photos.

The final photo, below, shows what the entire colony looks like.  All of these photos were taken in the Red Sea, but this species also can be found elsewhere in the Indo-Pacific region.