Cleaner fish

Cleaner fish are fishes that provide a service to other fish species by removing dead skin and parasites. This is an example of mutualism, an ecological interaction that benefits both parties involved. A wide variety of fishes have been observed to display cleaning behaviours including wrasses, cichlids, catfish, and gobies, as well as by a number of different species of cleaner shrimp. There is also at least one predatory mimic, the sabre-toothed blenny, that mimics cleaner fish but in fact feeds on healthy scales and mucous.

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Diversity of cleaner fish

Marine fishes

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 fishes such as these.^[1] 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.^[2]

  Cleaning behaviours have been observed in a number of other fish groups. Neon gobies of the genera Gobiosoma and Elacatinus provide a similar cleaning service 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^[2]. 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 spacially, and the overall benefit to the larger fish outweighs any cheating on the part of the smaller^[3].

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.^[4]

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.^[5]

Mimicry

The sabre-toothed blenny Aspidontus taeniatus is a blenny that mimics the cleaner wrasse. 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.^[6]

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.

References