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Keeping Cleaner Fish in Check

Sun, 10th Jan 2010

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Have you ever caught someone just before they say something embarrassing?  Did you give them a playful elbow?  Well, it turns out that cleaner fish do something quite similar.

Goatfish being cleaned by two cleaner WrassesCleaner fish are the little hangers-on you see on larger fish.  And their name is self-explanatory, they clean the larger fish of parasites and dead skin cells.  This ‘dirt’ is the cleaner fish’s food and it keeps the host fish happy, or at least prevents them from eating their followers.

Now Nicola Raihani and her team have found that male cleaner fish will punish the female cleaners if they step over the line and start munching on the tastier host fish, instead.  Because the host fish has a much more nutrient-rich mucous on their skin, and cleaner fish would much rather eat that, but it risks offending the host fish – which might mean the cleaner fish lose their food supply altogether.

In the journal Science this week; they tested this by offering the cleaner fish some fish flake feed and some more extravagant prawns. They trained the cleaner fish so that, if one took a bite from the prawns, all the food would be removed from the tank.  Very quickly, the researchers saw that whenever a female cleaner took a bite from the prawns the males would punish her by chasing her away.  And afterwards the females were much less likely to give into their prawny temptation again.

I’m not sure what it says about male-female relationships.  I know I get a telling-off if I reach for the chocolate.  Perhaps I’m offending the god of good female figures?  Raihani said "the males are less well behaved than the females a lot of the time but perhaps part of the reason the males are so likely to cheat is that females never punish males,"

But it might tell us something about the evolution of human behaviour and how we came to monitor each other’s behaviour for an overall benefit to the society.  Raihani suggests that, as the male fish are essentially looking after their own stomachs first, this is how behaviour which benefits the group as a whole might have evolved. 



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I take it the male refused to eat the prawn also having understand food would be lost, if they did so? If not that makes no sense.

If the males are refusing to eat the prawns and stopping the women doing so also, it implies they are seeking to protect the food sourses for everyone not just themsleves(they do not chace them away from the flakes).

Wiybit, Wed, 13th Apr 2011

I wonder if you could do another test and see which males twig quicker that eating the prawn, causes food to be lost, and then check out of all the males tested to see which of these males the female choose for a mate.

I bet the females will go for the smarter ones.

At a Guess I think it implies males are better at understanding the enviroment in colective survival terms, and females better at understanding males and enviromental needs for offspring(which is only an issue with offspring present).

As another experiment having a female with young in a tank with the prawn, could possibly lead to a role reversal where the female would chace the male away from the prawn, knowing that food would be with drawn(depending on the male ofcourse). Wiybit, Wed, 13th Apr 2011

Personally I think the female knows before the male about the shrimp and just likes getting chaced.

But the better provider under that sinario is the male that chases the female away.

Wiybit, Thu, 14th Apr 2011

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