June 22, 2004 | David F. Coppedge

Cleaners Advertise in the Fish Market

The plot of this science project seems made for Disney animation, a fishy version of Aesop’s parable of Androcles and the lion.  There are fish that will clean parasites out of the mouths and gills of their predators without getting eaten (see 01/13/2003 headline).  How these “cleaner fish” and their clients developed this risky relationship, a classic example of mutualistic symbiosis in which both parties benefit from the transaction, has long been a puzzle.  Alexandra S. Grutter (U. of Queensland) decided to do a science project on this phenomenon and published her results in the June 22 issue of Current Biology.1  Observing fish species from the Great Barrier Reef under lab conditions, she observed some interesting behavior that she termed “preconflict management strategy.”  It appears that with a bit of Madison-Avenue advertising skill, cleaners know how to clinch a deal in the fish market.
    Negotiations and compromises can result in unequal benefits, as in the fable of the contract between the man that needed a fur coat and the bear that needed a meal.  In the case of cleaner fish, Grutter showed experimentally that the “clients” (predators) normally have no qualms about munching on their little dentists.  They did eat the cleaner fish in certain situations without remorse.  The cleaners also have a natural aversion to swimming right into the mouths of their biggest threats, as seen in the fact that related fish won’t come near.  The variables in the experiment were: the parasite load on the client, the client’s hunger level, the cleaner’s hunger level, and the cleaner’s skill at preconflict management strategy.  There’s nothing like a little entertainment to break the ice.  Cleaner fish have mastered the feel-good commercial: they dance.
    Grutter observed the cleaner fish approach their dangerous clients with “tactile dancing”; they oscillate their tail fins and gently rub against the predator’s gills and body.  The client, apparently appeased by this show of good will, says, “OK, it’s a deal,” opens its mouth, and both get their satisfaction.  The cleaner fish seem to be able to sense when their clients are hungry, and respond by softening them up with more tactile dancing than usual.  (The cartoon becomes more entertaining at this point.)  But there is still a danger to the little serviceman.  Grutter and others have known that client fish will sometimes exhibit “posing” behavior, posturing themselves in a way that suggests readiness for cleaning.  How does the cleaner know it isn’t a trap?  It would seem the perfect ruse for a hungry predator to lie in wait, saving its energy, advertising itself that it just wants cleaning service, only to clamp its jaws shut on the do-gooders.  (See 04/26/2004 story about why animals rarely lie.)  It’s risky to do business with one’s enemies.  Most surprisingly, at the end of the cleaning, the client, now in a strength position, makes no effort to take advantage of the easy, gullible snack.
    How did this mutualism, sometimes termed reciprocal altruism, originate?  Grutter takes issue with the typical game theoretic approach (see 02/10/2004 headline).  Instead, she views her results supporting another approach: “The iterated prisoner’s dilemma has long been used to explain the evolution of cooperation between unrelated individuals, although some of its limitations have been illustrated with the cleaner fish mutualism.  Recently, biological market theory, in which traders exchange goods, services, or both, was proposed as an alternative for understanding cooperation in many systems, including cleaning symbioses.  Client ectoparasites and cleaning services are the main goods traded in the cleaner fish market.”
    It takes a skilled salesperson to convince a difficult, dangerous customer that she has a win-win offer that’s too good to refuse.  A Disney rendition of this story, with a timid yet fast-talking cleaner fish doing its little dance to appease the mean ol’ predator and get it to open up, is not hard to visualize.  And what hey, even tough guys need to see a dentist occasionally.  Maybe they fall for the best dancer.


1Alexandra S. Grutter, “Cleaner Fish Use Tactile Dancing Behavior as a Preconflict Management Strategy,” Current Biology,Vol 14, 1080-1083, 22 June 2004.

Personifying a phenomenon with an analogy does not explain its origin.  Neither game theory nor market theory provide adequate explanations in Darwinian terms for these interesting behaviors.  Fish are not capable of rational thought and market strategy.  If not designed, this behavior must be reducible to genetic and developmental factors.  If the predators always took advantage of the cleaners, there would be none left, and the phenomenon would disappear.  But the present is not the key to the past.  “Obviously, cleaning symbiosis has survival value for both types of species involved,” elaborated Gary Parker, a former evolutionist, in What Is Creation Science? (Master Books, p. 37).  “But does survival value explain the origin of this special relationship?” he asked.  “Of course not.  It makes sense to talk about survival only after a trait or relationship is already in existence.”
    In additional articles by Gary Parker, who used to teach evolution as fact, the conundrum posed by cleaning symbioses is acknowledged by Darwinians to be a problem for their theory.  Parker tells how Garrett Hardin, an evolutionist, once presented some startling questions in a Scientific American publication entitled, “Nature’s Challenges to Evolutionary Theory.”  He asked, “Is the evolutionary framework wrong?”  Taking note of the implication of design in such biological phenomena, he further suggested, “Was Paley right?”  Then, with a preconflict management strategy of his own, he proposed a fair deal that could provide a win-win situation for both sides.  He said, “Think about it.

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Categories: Marine Biology

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