Aggressive sea predators can be kept calm by cleaner fish

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London, July 5 : A new research has indicated that aggressive sea predators can be kept calm by cleaner fish that remove and eat the parasites off them, exchanging a grooming service for a tasty meal.

According to a report in New Scientist, researchers have previously shown that cleaners who enhance their service by touching the fish they are cleaning with their fins benefit from more cooperative clients.

This is especially helpful if the customer is a predator that could attack the cleaner. ut now, it seems that the calming effect of the cleaner fish's touch has wider repercussions.

"It makes hunters so mellow that it transforms the cleaning station into a safe haven for other fish," said Redouan Bshary at the University of Neuchatel in Switzerland.

"I've always marvelled at prey fish seeming so relaxed and non-vigilant at cleaning stations, even when lots of predators are around. A cleaning station should be a marvellous place for hunters to strike, but it never happens," said Bshary.

To test if cleaner fish influenced predators' behaviour towards prey, Bshary and colleagues from the University of Queensland in Brisbane, Australia, built mini coral-reefs in aquaria and observed the interactions between cleaners, their predatory and non-predatory clients and potential prey species that were not clients of the cleaners.

They found that predators in aquaria with cleaners chased prey two thirds less often than those in aquaria without a cleaner fish.

This peacefulness was not just a result of them having had less time to hunt because they were busy being groomed. Their aggression was suppressed even when they were not being tended to by the cleaner fish.

The number of chases also decreased the longer a cleaner spent touching a predator with its fins, and predators received at least three times as many touches as any of the other clients.

According to Jens Krause at the University of Leeds, interacting with a cleaner fish may trigger a simple behavioural switch in the predators, causing them to stop foraging.

"But it is still unclear if the cleaners actively mediate because they benefit from an overall peaceful environment, or if other fish receive protection simply as a side effect of the cleaner fish protecting itself," he said.

Bshary and colleagues want to test this by looking at whether cleaner ?sh stroke predators more when potential prey species are nearby.

They also intend to measure the predators' heart rate with hydrophones to see if the cleaners' massage has a physiological effect.


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