Science: Corals Signal to Gobies, "Come Clean Me!"

Corals use chemical cues to call goby fish to their aid when threatened by toxic seaweed, researchers report in the 9 November issue of Science. In return, the coral provide shelter and food for the fish.

Seaweed overgrowth is a major problem for coral reefs. All of the major stresses on coral reefs, from overfishing to climate change, encourage this growth, according to Georgia Institute of Technology researchers Danielle Dixson and Mark Hay. Seaweed seems to do its damage when it is in very close proximity to corals, so Dixson and Hay reasoned that the herbivorous fishes that live in the reefs might protect corals by eating seaweed that is growing on them.

Working in Fijian reefs, they analyzed communities of Acropora corals, which generate much of the reef's structural complexity, and their interactions with a variety of coral-dwelling fishes including gobies. Within minutes of contact by seaweed or even just seaweed chemical extract, the corals released an odor that recruited the gobies to trim the seaweed and dramatically reduce coral damage that would have otherwise occurred. Some gobies, in turn, become more distasteful to predators after eating the seaweed.

"The fish are getting protection in a safe place to live and food from the coral," Hay noted in a news release about the study. "The coral gets a bodyguard in exchange for a small amount of food. It's kind of like paying taxes in exchange for police protection."

Kathy Wren

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Corals provide goby fish with shelter and food in return for protection from natural enemies. [Slideshow courtesy of Science/AAAS]