When parasites build up on the skin of a reef fish, it can get relief by swimming over to a small, so-called cleaner fish that nibbles off the encrustations.
HOW WOULD YOU DESCRIBE THE RELATIONSHIP BETWEEN THE REEF FISH AND CLEANER FISH?
Mutualistic
Cleaner fish can also get food and nutrients by nibbling directly on the surface of the reef fish scales (a protective mucous coating). In fact, cleaner fish prefer the taste and nutrition of the mucous versus the encrustations.
WHY WOULD A CLEANER FISH NOT WANT TO NIBBLE ON THE SCALES?
The reef fish would swim away…and might not come back again later…..But:
"It's much more complicated than simple reciprocity" says behavioral ecologist Lee Alan Dugatkin of the University of Louisville in Kentucky, who has studied altruism.
WHAT IS SIMPLE RECIPRICOL ALTRUISM?
“Tit for Tat”, I help you and you help me.
In the team's previous observations, fish in the wild were less likely to bite one client when potential clients lingered nearby.
EXPLAIN THIS BEHAVIOR BY THE CLEANER FISH
It has been hypothesized that thecleaner-client system may be a case of indirect reciprocity, where a fish works attentively and holds back on taking a tasty nibble of the client's protective mucus coating, which would incite a jolt and perhaps a chase. By so doing, it wins an opportunity to clean a future client—the fish that watched. The idea that animals show generous behavior and reap benefits from those that observe it "has been floating around," says Dugatkin
DESIGN AN EXPERIMENT WITH CLEANER FISH AND CLIENT FISH THAT CAN SUBSTANTIATE THIS HYPOTHESIS.
Bshary and Grutter put a possible client, the bridled monocle bream Scolopsis bilineatus, in the middle compartment of an aquarium, where it could watch two cleaner fish, Labroides dimidiatus, in the end compartments. The researchers provided clients to each of the cleaners.
One cleaner, which got a client smeared with delectable prawns, worked diligently picking off the treats. The other cleaner, given a familiar, already clean client, largely ignored the visitor. Cleaner fish could not see the observer fish.
PREDICT HOW THE MONOCLE BREAM IN THE MIDDLE COMPARTMENT BEHAVED.
In 28 tests, the observer fish in the center compartment tended to hover nearer the compartment of the harder-working cleaner.
WHAT DOES THIS SHOW?
This shows that the client fish respond to more diligent cleaner fish. Clients engage in what is called image-scoring behavior.
WOULD YOU LIKE TO EXTEND THIS EXPERIMENT TO SHOW SOMETHING FURTHER?
But do cleaner fish work harder so that the same client fish will come back (simple reciprocity) or is it to impress observer fish so that they can get new clients?
DO YOU HAVE ANY IDEAS ON HOW TO SHOW THAT CLEANER FISH WORK HARDER AND ARE LESS LIKELY TO ENGAGE IN BITING BEHAVIOR IN THE PRESENCE OF OBSERVER CLIENT FISH?
In the earlier experiment, the cleaners couldn't see the observer. To see what might happen when the cleaners had an audience, researchers used pairs of food plates. The researchers stocked the two plates mixed with both ho-hum fish-food flakes and delectable bits of prawn. In one scenario, as long as the cleaner nibbled the flakes, the researchers left the second mixed plate. If the cleaner fish gulped a prawn, though, the researchers snatched away the second plate.
WHY DID THEY DO THIS? DRAW A PICTURE IF IT HELPS. WHAT IS THE PURPOSE OF THE DIFFERENT PLATES?
First plate=client fish being cleaned.
Second plate=future client fish that is observing.
If cleaner fish eat prawns from first plate=nibbling on client fish skin….then take away second plate (future client fish)
If cleaner fish eat ho hum food=parasites….then second plate remains (future client fish)
When researchers trained the cleaner fish with plate-snatching rules, the fish ate MORE OR LESS? of the uninspiring flakes when the second plate was nearby than when there was only one plate. When the two plates were available, the trained fish ate MORE OR LESS? flakes than a fish that hadn't been taught the rules.
SUMMARIZE HOW THESE FINDINGS MAY APPLY TO HUMAN BEHAVIOR AND ALTRUISM.
Humans are highly social animals and often help unrelated individuals that may never reciprocate the altruist's favor. This apparent evolutionary puzzle may be explained by the altruist’s (cleaner fish) gain in social image from image-scoring bystanders. (future client reef fish). These eavesdroppers notice the altruistic act and therefore are more likely to help the altruist (cleaner fish) in the future. Such complex indirect reciprocity based on altruistic acts may require two steps. First, image scoring evolves when bystanders gain personal benefits from information gathered, for example, by finding cooperative partners(first experiment) Second, altruistic behavior in the presence of such bystanders may evolve if altruists benefit from access to the bystanders(second experiment). "What makes this unique is that this study brings together audience effects and image-scoring in one system," says Dugatkin.