Common Wrasse (aka Blue Streak Wrasse) Labroides dimidiatus
Symbiotic relationship:
Mutualist relationship between Labroides dimidiatus and a variety host fish species

L. dimidiatus

There are five species of cleaner wrasse in the family Labroides. The Blue Streak or Common Cleaner Wrasse is the most widely known (Cleaner Wrasse). The Common Cleaner Wrasse (aka “Blue or “Blue Streak” Cleaner Wrasse) is a rather small fish, usually reaching only about four inches in length. It is a carnivorous fish that has the ability to maintain a mutualistic symbiotic relationship with nearly any other species of fish, ranging from very large in size to sometimes no bigger than itself. (Blue Streak Cleaner Wrasse) The relationship includes a meal for the wrasse along with temporary protection from its host. The host fish becomes rid of microscopic parasites invading its mouth and body. The cleaner wrasse is dependent on microscopic parasites obtained with its forcep like teeth to provide much of its nutrition. Thus, it needs to feed on quite a few of them to meet its basic nutritional value. Dead tissues from the host fish will also add to the wrasse’s meal (Gosnell).

Photograph of Labroides dimidiatus and its interaction with a moray eel

Feeding: Interaction with Host
The feeding behavior of Labroides dimidiatus is quite unique. Initiation of the symbiosis involves a soliciting “dance” performed by the wrasse. The host fish identifies the wrasse by its distinctive blue streak running laterally down its body (Blue Streak Cleaner Wrasse). Along with the wrasse’s distinctive bright colors, the dance helps larger fish recognize the cleaner (Salerno, 97). This action also intrigues and calms the host fish. The host fish then proceeds to perform a certain movement or series of movements, providing the cleaner fish access to its body surface, fins, gills, and in most cases its mouth (Cleaner Wrasse). When it comes to specificity of cleaning location on the client fish, both juvenile and adult Labroides dimidiatus seemed largely in favor of the body. This is where the mucus of the host fish is located, which is often ingested by wrasse even if no parasites are present. In one study, only in one case did cleaning occur on the mouth, gills, and body of the same client fish. Observing host specificity, only juveniles were seen to display preferences for smaller fish, as to be cautious against predation from larger hosts. (Salerno, 102).
Common Wrasse cleaning a host client's mouth

Cleaning Station
After the cleaner wrasse inspects the host by fanning it with its ventral fin, it proceeds to obtain its meal. This process is often carried out at designated “cleaning stations” where fish can arrive to receive the service (CleanerWrasse). Feeding stations are usually located underneath a piece of reef or boulder that juts outward creating an overhang. When studying single working wrasse, most juveniles were found to perform cleaning at one such “station”, while some adults will provide services in more exposed settings. The adult cleaner stations were found to be twice as large in area ( >4 square meters) than the juvenile cleaning stations(>2 square meters). Researchers also found that the average cleaning time per client fish for adults was less than that of juveniles. Further, the ratio of cleaned fish by adults vs. that of juveniles equaled three to one. Since juveniles were found to be cleaning a smaller number of fish, they needed to spend more time in the process in order to gain enough nutritional benefit (Salerno, 99).

Watch a Cleaner Wrasse in Action, Cleaning a Barracuda's mouth!

“Cheating” while feeding occurs habitually. The mucus from the skin of a fish provides a more satisfying meal than just the parasites and dead skin alone, so the wrasse are often tempted to take a larger bite than they should. As one can imagine, this does not provide for a happy host fish. The client fish will leave the station if they are cheated. The cheating appears to be purposely performed, since surprisingly cheating is reduced when cleaners notice they are under the watch of other client fish. (Douglas, 65). Each cleaning station is considered a territory for either a single wrasse or a pair of wrasses to utilize. (Salerno, 97). The cleaning is sometimes carried out by a single fish, or by a pair of fish in which they act together on the same host. When serving in two’s, research displayed the pair is almost always comprised of one female and one male. In this case, the female contributes more towards the quality of cleaning. However when observing cleaning ability of solitary wrasse, there were no significant differences between the sexes (Bshary, 964). It was found that when a host fish was cleaned by a pair, the service was better than when the cleaner worked alone (Swedish Research Council). The benefits of cheating can only be gained by one partner in the pair, since the clients will leave in response to a cheating bite (Bshary, 964). Interestingly, researchers suggest that males will “aggressively chase females” who perform the cheating act. It will seem to the client that the male is acting to protect it, though the male is really just looking out for his best interest in feeding himself. Researchers also noted that if the cleaners work together and “watch each other’s behavior”, they seem to pass up taking the appealing cheat bite more often (Zoological Society of London).

Social Behavior
Labroides dimidiatus has a social behavior that is far from ordinary. The Blue Streak cleaner wrasses start their lives primarily as females. For every small group of cleaner wrasses there is usually only one male present. Thus, female fish are much more common in nature than males. If the male happens to die, a female can actually change her sex to become the new male. This happens by the process of sequential hermaphroditism (The Ideal Relationship). The ability to change sex can raise further question about competitive levels between female hermaphrodites and already existing males.

Aspidontus taeniatus, also known as the sabor-toothed blenny, is an impostor of the cleaner wrasse. The blenny resembles the cleaner fish in size, shape, and coloration. The L. dimidiatus vary slightly in coloration and markings based on different geographical locations, which the benny is able to match (Douglas, 66). This disguise allows it to protect itself from predators, or approach prey without alarming them (Paracer, 205). A. taeniatus is remarkable in its close resemblance to the cleaner wrasse. It even performs a similar dancing movement that causes the prey to prepare for cleaning (or so they think). Thus, they mock the wrasse in both appearance and behavior (Wickler, 473). Most experienced client fish can differentiate a real cleaner wrasse and a mimic, thus the young and inexperienced fish are usual the victims. (Douglas, 66)

Aspidontus taeniatus, resembling a Blue Streak Cleaner Wrasse


-“Blue Streak Cleaner Wrasse” About Fish Online (2008) Web. 06 Apr 2011.
-"Cleaner Wrasse" Animal-World (2011) Web. 08 Apr 2011.
-Gosnell, Jeremy. "Cleaner Wrasse" - Fish Channel (2011) Web 06 Apr 2011.
-Bshary, R., Grutter, A. S., Willener, A. S. T., & Leimar, O. (2008). Pairs of Cooperating Cleaner Fish Provide Better Service Quality than Singletons. Nature. 455(7215), 964-966.
-Douglas, Angela E. The Symbiotic Habit, Princeton, NJ, Princeton University Press (2010) p.64-66
-"The Ideal Relationship - Blue Streak Cleaner Wrasse" Wild Facts (2010) Web. 06 Apr 2011
-Paracer, S., Ahmadjian, V. Symbiosis: An Introduction to Biological Associations, New York, Oxford University Press (2000) Ed. 2 p. 205
-Salerno, Daniel J., The Feeding Activities of the Cleaner Wrasse, Labroides dimidiatus (Valenciennes), in the Shallow Waters of New Caledonia and Fiji Beta Beta Beta Biological Society, (1991), 62.4 pp. 97-103
-The Swedish Research Council. "Pairs Of Cleaner Fish Co-operate And Give Better Service On The Coral Reef." ScienceDaily, 4 Nov. 2008. Web. 14 Apr. 2011.
-Wickler, W. "Mimicry in Tropical Fishes" Philosophical Transactions of the Royal Society of London - The Royal Society, 251(772) p. 473-474
-Zoological Society of London. "Reluctant hero? Cleaner fish show it pays to be selfless." ScienceDaily, 12 Jan. 2010. Web. 27 Apr. 2011.