Cleaner fish

A cleaner fish feeds on parasites, dead tissue, or mucus from larger animals, often at designated cleaning sites. The interaction can benefit both cleaner and client, though cleaners sometimes cheat by biting healthy tissue.

Cleaning station: A site where cleaner animals repeatedly remove parasites or tissue from visiting clients. Clients gather at these sites, turning cleaning into a repeated interaction rather than a chance encounter.
Bluestreak cleaner wrasse: A small Indo-Pacific wrasse that establishes cleaning stations and removes ectoparasites from reef fishes. It is one of the best-studied dedicated cleaner fishes.
Mutualism: An interaction between species in which both participants gain a benefit. Cleaner-client relationships are a well-known example, although cheating can make benefits unequal.
Cheating in mutualism: Behavior in a mutualism that gains benefits while reducing or withholding the partner's expected benefit. Some cleaners bite healthy mucus-rich tissue instead of removing parasites.
Fish self-awareness: The question of whether fishes possess forms of self-awareness, including recognition of their own bodies. Cleaner wrasse mirror-test results have fueled disagreement about what counts as self-recognition.
Cleaner wrasse: A wrasse that feeds on ectoparasites and tissue from visiting reef fishes. This fish is a prominent example of specialized cleaning behavior on coral reefs.
Spanish hogfish: A Caribbean wrasse that cleans parasites from larger reef fishes, especially as a juvenile. Its cleaning role changes with age, illustrating that cleaning can be a life-stage strategy.
Reciprocal altruism: Cooperation in which an individual benefits another and may receive a benefit in return later. Repeated visits can make present restraint worthwhile when clients return.
Parasitism: An interaction in which one organism benefits while harming another organism, its host. A cleaning encounter can shift toward parasitism when the cleaner's feeding harms the client.
Animal consciousness: The capacity of nonhuman animals to have subjective experiences. Claims about cleaner-fish cognition raise broader questions about how animal minds can be inferred.

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