Monday, September 29, 2003


Bruce Long writes

“I have been following the recent discussion on monkey ethics. It seems to me that there is a much better example of ethics and fair play in the animal kingdom, one that involves fish. As an active SCUBA diver I am aware of, have seen, and actually have participated in a “cleaning station”.

Fish have some severe problems in the area of dental hygiene. They too suffer from pieces of food stuck between their teeth. More of a problem are the opportunistic algae and other parasites that colonize their gills. Nature has evolved a solution to this problem, the cleaning station. A cleaning station is a prominent outcrop of coral with one or more small shrimp. The customer fish swims up to the cleaning station and opens his mouth. The shrimp swim into the open mouth and make a meal on the food debris, and parasites present in the teeth, mouth area and gills. The customer fish gets a good flossing and cleaning and the shrimp get a free meal.

So here you have a fish with several tasty shrimp in his mouth. The fish appears to understand the short term gain of a quick and easy meal is not worth losing the clean service provided by the shrimp. But the "moral" behavior of the fish does not end here. It turns out the services of the cleaning shrimp are much in demand, so much so that a line forms. I have seen cleaning station with five or more fish patiently waiting in line. So it appears fish understand the concepts "of get in line" and "wait your turn". Even more amazing there is an apparent moratorium on predatory behavior as it is common to seen a large predatory fish patiently waiting in line with a small prey fish just inches in front of its nose. Both fish seem to understand that cleaning station customers do not eat other cleaning station customers.

It is possible for a SCUBA diver, if he moves slowly and carefully to take a place at the end of the line. I have done this and when my turn at the cleaning station came I put out my hands for inspection. The shrimp looked a little confused but they examined my hands and worked a bit on the cuticle of my fingernails before deciding I had no parasites to speak of . The returned to the coral pinnacle to wait for the next customer.

Cleaning stations are not at all uncommon on tropical coral reefs although they can be easily disturbed by the activity of a large number of divers. I seem to remember an article in a diving magazine about 15 years ago. If I remember correctly the diving community was widely aware of the phenomena of cleaning stations but it seem it was not entirely taken seriously by the marine biology community. This impression could well be wrong or out of date but I am unaware of any discussion of the cleaning station morals in the scientific literature. To be fair, as an electrical engineer, I have no contact with the marine science community so whatever I think I know in this area is second hand knowledge at best.

In any event it seems reef fish of many species have a well developed sense of fair play and understand at least in one circumstance, the postponement of short term gain for long term benefit. I find this truly amazing and rather more convincing than the recent monkey experiment.

The creationist people use cleaning stations as evidence of intelligent design. I don't quite believe this but I have no idea how to explain the development of cleaning stations in terms of Darwinian evolution.”

Cheney, K.L. and I.M. Cote. 2001. Are Caribbean cleaning symbioses mutualistic? Costs and benefits of visiting cleaning stations to longfin damselfish. Animal Behaviour 62:927-933.


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