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Published online 29 September 2008 | Nature | doi:10.1038/news.2008.1139
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Underwater cleaners keep the peace
Piscine predators distracted from hunting during their trip to the spa.
Only humans and a handful of other primates will attempt to make peace between warring third parties. But now there is a new diplomat on the block: the cleaner wrasse.
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Could it also be that they clean more with more prey around so that the predator gets to do more stuff (because of more prey) until it returns again? Effectively, they know the predator will be gone having fun for a longer time, so they want to massage/eat more parasites, say if cleaning got them to scrape off more food to be picked up later from the bed? I really doubt cleaner fish to be peace makers from an objective point of view, unless of course they can instinctively compute complexity within a certain cocoon of cooperation. I'd like to be proven wrong.
This is very intriguing, but did the observers know the reason for the experiment? It would be reassuring if they did not know the hypothesis or question and were simply told to count the numbers of attacks in each tank. If the observers did know, that might bias what they recorded, or at least raise doubt about it.
In order to get cleaned in the first place, predatory fish must have to suppress their instincts to eat the cleaner fish - as the picture associated with the article graphically demonstrates. It seems like it would be a lot easier, neurologically, to suppress all predatory tendencies, rather than trying to wire specific circuits for all particular species of cleaner wrasse and cleaner shrimp. It's hard for me to even imagine how you could wire those specific recognition circuits without a long entrainment time - which would be tough on the cleaners. Very interesting!
The idea of fish having 'modes' of behaviour, and not mixing them up, is an old one in fishing circles, that I have read and heard a few times, although certainly not in a scientifically researched context. Based on my long career of unsuccessful fishing, I think my throwing in a baited hook is just as likely as a cleaner species to put fish into a social or travel mode.