Cleaner fish

Two cleaner wrasses Labroides dimidiatus removing dead skin and external parasites from the grouper Epinephelus tukula.

Cleaner fish are fish that provide a service to other fish species by removing dead skin and ectoparasites. This Cleaning symbiosis is an example of mutualism, an ecological interaction that benefits both parties involved, though cleaning may grade into parasitism.

A wide variety of fishes have been observed to display cleaning behaviors including wrasses, cichlids, catfish, and gobies. Similar behavior is found in a number of species of cleaner shrimp.

Cleaner fish advertise their services with conspicuous coloration, often consisting of a bold blue stripe the length of the body. By convergent evolution, different species of cleaner fish often resemble each other. There is also at least one aggressive mimic, the sabre-toothed blenny, that looks like a cleaner fish but in fact feeds on healthy scales and mucus.

Diversity of cleaner fish

Marine fishes

A White-spotted puffer being cleaned by a bluestreak cleaner wrasse

The best known cleaner fish are the cleaner wrasses of the genus Labroides found on coral reefs in the Indian Ocean and Pacific Ocean. These small fish maintain so-called cleaning stations where other fish, known as hosts, will congregate and perform specific movements to attract the attention of the cleaner fish. Remarkably, these small cleaner fish will safely clean large predatory fish that would otherwise eat small fish such as these. Cleaner wrasses appear to get almost all their nutrition through this cleaning service, and when maintained in aquaria rarely survive for long because they cannot obtain enough to eat.

Caribbean cleaning goby Elacatinus evelynae

Cleaning behaviors have been observed in a number of other fish groups. Neon gobies of the genera Gobiosoma and Elacatinus provide a cleaning service similar to the cleaner wrasses, though this time on reefs in the Western Atlantic, providing a good example of convergent evolution. Unlike the cleaner wrasses, they also eat a variety of small animals as well being cleaner fish, and generally do well in aquaria. However, the Caribbean cleaning goby (Elacatinus evelynae) will gladly eat scales and mucus from the host when the ectoparasites it normally feeds on are scarce, making the relationship somewhat less than mutually beneficial. The symbiosis does not break down because the abundance of these parasites varies significantly seasonally and spatially, and the overall benefit to the larger fish outweighs any cheating on the part of the smaller.

Brackish water fishes

An interesting example of a cleaning symbiosis has been observed between two brackish water cichlids of the genus Etroplus from South Asia. The small species Etroplus maculatus is the cleaner fish, and the much larger Etroplus suratensis is the host that receives the cleaning service.

Freshwater fishes

Cleaning is notably less common in freshwater habitats than in marine habitats. One of the few examples of cleaning is juvenile Striped Raphael catfish cleaning the piscivorous Hoplias cf. malabaricus.

Mimicry

Many cleaner fish have a distinctive combination of a long narrow body, a longitudinal stripe, a blue colour, and small size. "Convergent signalling among cleaners, using size, stripes and colour, should facilitate their recognition by fish clients."

The sabre-toothed blenny Aspidontus taeniatus is a blenny that mimics the ritualised dance the cleaner wrasse makes when passing fish swim by. Instead of providing a useful cleaning service, however, it bites off pieces of healthy skin and scales from the host before darting away to safety.

See also

• Doctor fish, fish that provide a cleaning service to humans.
• Reciprocal altruism
• Social grooming, cleaning services offered between members of the same species.
• Surgeonfish, named for the scalpel-like blades near their tails.
• Tinca tinca, known as the "doctor fish" in the UK.

External links

Media related to Cleaner fish at Wikimedia Commons