Terrorized “care salons” in the coral reef

Video © Cambridge University
“Business-damaging” behavior in the underwater world: Researchers have found that some species of bass chase away “customers” from cleaner fish. The phenomenon may have ecological significance: in damaged coral reefs, the number of troublemakers could increase and thus their negative effect on the fishy “cleaning service”. The scientists say that this would affect the sensitive environment even further.

Mutually beneficial relationships between different living beings are among the most fascinating phenomena in the animal kingdom. The coral reefs of the world offer a particularly interesting example. There, certain species of fish feed on parasites and pieces of dead skin from other reef inhabitants, who in turn appreciate these “services” very much. In the Caribbean, the shark nose gobies (Elacatinus evelynae) take on the role of cleaner fish. The small, black and white striped fish work alone or together with others at nursing stations that they set up at certain points on the coral reef.

Many species of fish can then be treated “professionally” there. The “customers” adopt a motionless posture and seem to enjoy the procedure. “In return for their services, the gobies receive payment in the form of food – parasites and dead skin fragments,” says lead author Katie Dunkley of the University of Cambridge. Previous studies have already shown that the cleaning service is important for the health of the reef inhabitants: if there are any impairments, the population and biodiversity in the fish community suffer.

Spotlight on cleaning stations

To further explore this interesting and important service system in coral reefs, Dunkley and her colleagues targeted cleaning stations at various locations on a shallow coral reef off the Caribbean island of Tobago. For their study, they evaluated extensive observation data of the visitors and their behavior. Basically, it was again shown that a motley clientele stopped by the cleaner fish: representatives of the parrot fish, surgeon fish, butterfly fish and also damselfish can be found there.

As the researchers report, however, the latter have a special meaning: The team found that damselfish species that claim territories for themselves can be problematic for the “care salons”: They scare away customers and thus have a “damaging effect on business”, is characterized in significantly different from the observations. Damselfish defend their territory by repelling intruders with bites, attacks, pursuit or threats. I thought damselfish might have a special role at cleaner fish stations, but to see how influential they are was amazing,” says Dunkley. It is a case where a beneficial relationship system in nature is disrupted by a third party, the researchers point out. To stay in the picture of economics, Dunkley says: “If the customers are excessively absent from it, a cleaning station will go out of business over time,” according to the behavioral ecologist.

Troublemakers on the rise?

Basically, it is obviously a natural aspect in the network of relationships of the reefs. But in the future, the behavior of the damselfish could have an increasingly negative effect, say the scientists. Because the widespread impairment of coral reefs due to climate change and over-fertilization of the water could cause their stocks to grow excessively. Territorial damselfish feed on algae, which thrive better under these circumstances. Thus, the cleaning stations could increasingly fall into the territory of damselfish. “As coral reefs deteriorate, damsel fish may help fewer species receive health-critical cleaner fish cleaning,” says Dunkley. This could ultimately contribute to the further decline of the sensitive ecosystems, explains the researcher.

She and her colleagues now want to investigate these complex connections further. “It’s important that we don’t just look at relationships in lifeworlds in isolated bubbles. We need to take a step back and see how all fish are connected so we can protect ecosystems like coral reefs,” concludes Dunkley.

Source: Cambridge University, professional article: Behavioral Ecology, doi: 10.1093/beheco/arac122

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