Labroides dimidiatusBlue streak(Also: Bridled beauty; Cleaner fish; Common cleaner wrasse; Gadfly fish)

Geographic Range

Blue streak wrasses inhabit Indo-pacific coral reefs, including the Great Barrier Reef. They range from Queensland and the South Seas through the East Indies to the Red Sea, Zanzibar and Mauritius (Marshall, 1964)


Striped cleaner wrasses tend to dwell in coral or rocky areas on coral reefs (Roughley, 1951). They are commonly found in waters adjacent to shallow coral outcrops along the Great Barrier Reef (Grant, 1978). They are also seen in tide-pools. (Smith, 1965)

They are not migratory.

  • Aquatic Biomes
  • reef

Physical Description

Adult blue streak wrasses usually grow to be 4 inches long (Grant,1978).

Wrasses possess a smooth, compressed, elongate body with a pointed snout. They have small mouths with prominent lips. They have jaws and teeth, particularly 2 canines that are curved anteriorly in each jaw.

Wrasses have a rounded caudal fin along with a dorsal fin consisting of 9 spines and 9-11 rays and an anal fin with 2-3 spines and 9-10 rays (Marshall, 1964). Wrasses have very small scales and the head is normally scaleless.

Blue streak wrasses are brilliant blue with a broad jet-black band that runs from the tip of the snout to the end of the tail, starting out narrow at the anterior end and gradually broadening towards the posterior end. This band usually takes up most of the tail, except the upper and lower rays which are a shade of blue (Marshall, 1966). Young wrasses are sometimes all black, except for a pale streak along the lower, upper and back caudal rays (Marshall, 1964).

The colors of young and adult wrasses differ (Smith, 1965). They are also known to change colors based on mood (Grant, 1978).

There is no geographic variation in morphology or coloration.


Wrasses practice external fertilization in which the female's eggs are released into the water. Mating usually occurs at twilight (Flying Fish Express)

Large males defend reef territories and attract multiple females to these territories, usually by performing a beautiful mating dance. Females live within these territories and spawn with the male. Fertilized eggs form planktonic larvae that move freely with the ocean currents. If the territorial male leaves or dies, the most dominant female will take his role and become male within the next 24 hours. She assumes the territory and mates with the rest of the females.


  • Average lifespan
    Status: captivity
    4 years


Usually 1 to 3 cleaner fish occupy a single cleaning station. These cleaning stations are often permanent.

Wrasse are quick and agile swimmers, weaving in and out of crevices and tunnels amongst the rocks of the reef

(Smith, 1965)

Well-defined social groups of these wrasses consists of one dominant male and multiple females. When the male dies or leaves, the most dominant female replaces him. Within the next 24 hours her sex changes and she becomes male (Grant, 1978).

These fish are diurnal and are able to sleep, an unusual behavior and ability amongst fish. When darkness encompasses the ocean, wrasses burrow into the sand on the ocean floor and produce a mucous envelope where they remain until sunrise (Roughley, 1951)

Communication and Perception

Food Habits

Wrasses are carnivorous. Their diet consists primarily of parasitic copepods and other invertebrates that are taken from the mouth and gill openings of larger fish. They also feed occasionally on free-swimming crustaceans.

Blue streak wrasses are known as common cleaner fish that set up cleaning stations on various parts of coral reefs, usually 3-10ft. deep. They attract larger fish to their stations by making strange, oscillatory swimming movements, and the fish then stop to get cleaned. Wrasses enter the mouth and gill openings and remove any ectoparasites and diseased tissue. The larger fish not only refrain from devouring these small cleaner fish, but actually readily open their mouth and gill cavities so that they are able to clean.

This is clearly a mutualistic relationship between cleaner wrasses and various larger fish of the ocean (Grant, 1978).

Economic Importance for Humans: Positive

Cleaner wrasses benefit humans by increasing the survival of various economically important fish. They increase the survival of larger fish by eating and removing harmful parasites and diseased tissue from their scales and body.

Economic Importance for Humans: Negative

Wrasses are not known to have any negative affects on humans.

Conservation Status

Other Comments

A similar species, L. aspidontus, closely resembles L. dimidiatus. Members of this species swim in an oscillating motion, as the wrasse does, and when larger fish open their mouths to be cleaned, swims inside and rips off pieces of skin (Roughley, 1951).


Lisa Evans (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.


Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.


uses touch to communicate


"Flying Fish Express" (On-line). Accessed April 8, 2000 at

Grant, E. 1978. Guide to Fishes. Brisbane, Queensland: The Department of Harbours and Marine.

Marshall, T. 1964. Fishes of the Great Barrier Reef *and coastal waters of Queensland*. Sydney: Angus and Robertson LTD.

Marshall, T. 1966. Tropical Fishes of the Great Barrier Reef. Sydney: Angus and Robertson LTD.

Roughley, T. 1951. Fish and Fisheries of Australia. Sydney: Angus & Robertson LTD.

Smith, J. 1965. The Sea of Fishes of Southern Africa, 5th Edition. South Africa: Central News Agency LTD.