Worms with Hard Hats

by David Sugarman

How do coral reefs form? It seems to be with the help of marine worms.

Scientists in Morocco noticed that small pieces of living coral in an aquarium had moved up to 16 cm one night and were stuck to the sides of rocks with a glue-like material.

When the scientists moved the corals back to their initial positions, the next morning the coral had moved yet again. This happened over and over.

But coral can't move on their own. Something in the tank was doing it, and it only happened in darkness.

Using an infrared camera (sensitive to heat, not visible light) they filmed a small worm no thicker than a shoe lace and about 3 cm long, grabbing the coral, moving them, and sticking them to the rock. And it did this very quickly — in less than 2 seconds!

The pieces of coral were little, weighing up to 20 grams, but since these worms can grow up to 2 metres in length, they could move fairly large chunks of coral, too.

And to top it off, even though it was working in the dark, the worm always stuck the coral onto the rocks so that the coral would be exposed to light, which is vital to keeping it alive. How did the worm know which end was up?

By moving coral in order to build homes for themselves, these eunicid worms can help to lay the foundations of coral reefs, which provide habitats for an incredible variety of life.

Vast coral reefs engineered by worms. Go figure.