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NOCTURNAL worms with powerful home-making instincts may have laid the
foundations of some of the world鈥檚 great coral reefs, researchers in Australia
believe.

For reefs to grow, early settlers need a firm footing鈥攏ewly formed
volcanic rock, for instance. Yet massive reefs such as the Great Barrier Reef
have grown up on shifting sediments with no obvious solid foundation. John
Chisholm, of the European Oceanological Observatory in Monaco and Russell Kelley
of Watermark Films in Townsville, Australia, suggest that common marine worms
called eunicids could have seeded the growth of such reefs.

Chisholm and Kelley kept a tropical marine aquarium in Townsville. One
morning they were astonished to find that small colonies of the coral
Lobophyllia hemprichii had moved across the tank during the night. They
moved them back, but the same thing happened night after night. 鈥淭hey always
ended up on the same piece of rock, so something must have been putting them
there,鈥� says Chisholm.

An infrared video camera solved the mystery. After dark, the researchers
filmed a worm popping out of a hole in the rock and grabbing a coral colony in
its jaws. The worm then withdrew and stuck the coral in place part way up the
rock with a glue-like substance. On some nights it moved three or four colonies.
鈥淎s the worm grows it needs to build a bigger home, and anything it can stick on
will do,鈥� says Chisholm. They recorded the worm carrying corals weighing up to
20 grams over distances as large as 16 centimetres.

Eunicid worms can grow more than 2 metres long and must be capable of
amassing sizeable patches of rubble, says Chisholm. Such patches attract corals
and coralline algae larvae. 鈥淭he worms don鈥檛 build reefs but provide the
conditions reefs need to grow,鈥� he says.

鈥淚t would be nice to know how many worms really do this,鈥� says Brian Rosen, a
reef expert at the Natural History Museum, London. 鈥淯ntil then we can鈥檛 say if
this is a one-off or whether worms are a significant agent in forming reef
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