The Cleaner Wrasse - Helping to Keep Fish Parasite Free

The ecologically diverse coral reef at our backdoor is home to over 4,000 species of fish. All these species play a role in the reef ecosystem; some fish provide food for other animals, while others clean damaging algae from the reef. Still other species have symbiotic relationships with other fish, a relationship in which both species benefit. One of the most striking examples of symbiosis involves the cleaner wrasse. This fish is responsible for setting up what are known as "cleaning stations," providing a valuable service to other fish by picking off and "cleaning" its customers of parasites and dead tissue. The wrasse, in turn, receives nutrients from the parasites and tissue.

    The parasites that the wrasse consume are organisms that live on or within the body of a host, in this case a fish. Often, parasites are simply small crustaceans that live between the scales of fish and feed on its tissue. It is not known whether these critters, which are a fact of life for many fish, are anything more than an annoyance, but it is clear that most fish prefer to have them removed. For this removal, many fish turn to the cleaner wrasse to get the job done.

Reef Brief is a weekly column published in the San Pedro Sun
    The cleaner wrasse, one of 600 species of wrasse, is found along coral reefs worldwide and usually choose a home along the reef that is popular among fish to set up its cleaning station. At this location, various fish literally line up and wait to be "cleaned" by the wrasse. This is one of the few cases in which varying species of fish actually inhabit the same space without becoming territorial or aggressive with each other. It's clear that these fish have one thing on their mind when they line up at the cleaning station: getting the parasites removed as soon as possible. Easily distinguished by a bright blue and yellow band, the cleaner wrasse makes an effort to advertise its services by performing a dance. Likewise, when a fish wants to be "cleaned" it sends specific signals to the wrasse, such as keeping its body stationary, while spreading its fins and gills and opening its mouth. If the wrasse picks up on the signal it will begin the cleaning process on its customer, which is usually a larger fish. Cleaning consists of the wrasse swimming over the entire body of its customer, eating parasites from the fins and gills. The wrasse will even go inside the mouth and clean between the teeth of its customer. Interestingly enough, the wrasse is rarely injured or eaten by the other fish; the wrasse vibrates its fins while cleaning to remind its customer of its presence. Moreover, the cleaned animal will frequently defend the cleaning station and its cleaners from attack by would-be predators.

     Almost all marine species are actively involved in close symbiotic relationships with at least one other species in their community. The unique relationship between the cleaner wrasse and the fish it cleans at the "cleaning stations" are an important and impressive example of symbiosis. Not only does the satisfied customer leave parasite free, but also the wrasse enjoys a protein rich meal.

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