Cleaner Wrasse

Labroides dimidiatus is a small marine wrasse known for cleaning other reef fishes. It is also called the common cleanerfish.

Look for a slender fish with a pale head, blue rear body and tail, and a broad black stripe running along each side. Juveniles look different: they are black with a bright blue stripe.

Fishes of Australia gives a maximum total length of about 12 cm, including the tail.

It occurs widely in the tropical and subtropical Red Sea and Indo-Pacific. Australian records extend roughly from Perth around the north to Sydney, with records from several offshore islands.

It is associated with reefs. Fishes of Australia lists a depth range of about 2–40 m; cleaning stations can occupy conspicuous places such as coral outcrops.

It picks external parasites from other fishes, especially small crustaceans such as gnathiid isopods. It also eats mucus from the clients’ skin, which can put the interests of cleaner and client in conflict.

It is a place on the reef where the cleaner works and client fishes visit for parasite removal. A small social group may use the station, with a dominant male and several females.

Its characteristic swimming display advertises cleaning services to prospective client fishes. A client can then approach and allow the wrasse to inspect its body for parasites.

Not always. In a 2003 feeding-choice experiment, cleaners preferred client mucus and parasitic flatworms over the commonly eaten gnathiid isopods. Taking a client’s protective mucus is described as cheating in this relationship.

A 2002 study found that clients often ended an interaction after a jolt associated with cleaner contact. Depending on access to other stations, clients could chase the cleaner or leave to seek another partner.

Yes. If a group loses its male, the largest female can become male. The direction can also reverse: experiments have documented males becoming female in changed social circumstances. Sex change is influenced by social relationships.

Predators also benefit from parasite removal and commonly tolerate cleaners during these visits. This is no guarantee of safety: a 2017 study found that cleaners retain strong escape performance, and dissatisfied clients can chase them.