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Corals signal to gobies, 'come clean me!'

The goby (Gobiodon histro) that lives in the coral (Acropora nasuta), approaching the toxic seaweed (Chlorodesmis fastigiata) to remove it.
[Image courtesy of Danielle Dixson]

On the reefs of Fiji, corals and goby fish help each other out, a new study shows. The corals offer the gobies food and shelter, and the gobies protect the corals from toxic seaweed.

Seaweed overgrowth is a major problem for coral reefs. The seaweed damages the corals and competes with them for space.

Danielle Dixson and Mark Hay of the Georgia Institute of Technology thought that some of the fishes that live in the reefs might protect corals by eating seaweed that is growing on them.

Working in the Fijian reefs, they studied communities of Acropora corals and their interactions with gobies and other coral-dwelling fishes.

Within minutes of contact by seaweed or even just a chemical from the seaweed, the corals released an odor that summoned the gobies to come trim the seaweed. This dramatically reduced the damage to the corals. The gobies, in turn, become more distasteful to predators after eating the seaweed.

This type of relationship, in which two species help each other, is called a "mutualistic relationship."

The research appears in the 9 November 2012 issue of the journal Science.