Bluestreak cleaner wrasse

The bluestreak cleaner wrasse (Labroides dimidiatus) is one of several species of cleaner wrasses found on coral reefs from Eastern Africa and the Red Sea to French Polynesia. Like other cleaner wrasses, it eats parasites and dead tissue off larger fishes' skin in a mutualistic relationship that provides food and protection for the wrasse, and considerable health benefits for the other fishes.

Description
This is a small wrasse, averaging 10 cm long, at most 14 cm. It can be recognized thanks to a wide longitudinal black stripe running along the side and eye; the back and the stomach are white (sometimes slightly yellowish). This white part changes to a bright blue on the front of the animal, while the black band widens at the tail. The young are black with an electric blue line.

A genetic analysis of L. dimidiatus revealed the population fell into two monophyletic clades, with Indian Ocean populations generally having different stripe widths to western Pacific fishes. The Japanese cleaner wrasses, though, fell within the same group as Indian Ocean fish, despite differing in appearance, and both clades overlap around Papua New Guinea. Two closely related cleaner wrasse species, Labroides pectoralis and Labroides bicolor, were grouped inside the L. dimidiatus clade, so the bluestreak cleaner wrasse may in fact be polyphyletic, incorporating several species.

Distribution
The bluestreak cleaner wrasse is found on coral reefs in the tropics from the Red Sea and Indian Ocean to the western Pacific (including Papua New Guinea, Japan, Fiji, and French Polynesia). It was first recorded from the Kermadec Islands Marine Reserve north of New Zealand in 2015, after researchers examined hundreds of hours of unused documentary film footage.

Cleaning
Cleaner wrasses are usually found at cleaning stations. Cleaning stations are occupied by different units of cleaner wrasses, such as a group of youths, a pair of adults, or a group of females accompanied by a dominant male. When visitors come near the cleaning stations, the cleaner wrasses greet the visitors by performing a dance-like motion in which they move their rear up and down. The visitors are referred to as "clients". Bluestreak cleaner wrasses clean to consume ectoparasites on client fish for food. The bigger fish recognise them as cleaner fish because they have a lateral stripe along the length of their bodies, and by their movement patterns. Cleaner wrasses greet visitors in an effort to secure the food source and cleaning opportunity with the client. Upon recognising the cleaner and successfully soliciting its attention, the client fish adopts a species-specific pose to allow the cleaner access to its body surface, gills and sometimes mouth. Other fish that engage in such cleaning behavior include goby fish (Elacatinus spp.) The bluestreak cleaner wrasse is known to clean balaenopteridae, chondrichthyans, homaridae, octopodidae, and dermochelyidae.

Some fish mimic cleaner wrasses. For example, a species of blenny called Aspidontus taeniatus has evolved the same behavior to tear small pieces of flesh or skin from bigger fish rather than rid them of parasites. Another species, the bluestreak fangblenny, Plagiotremus rhinorhynchos, mimics juvenile cleaner wrasse so its presence is tolerated by the cleaners, which, it is assumed, enables it to take advantage of the concentration of potential victims.

In different regions, the bluestreak cleaner wrasse displays various degrees of dependency on clients' ectoparasites as a primary food source. In tidal environments such as the Great Barrier Reef, the bluestreak cleaner wrasse is a facultative cleaner that feeds more on corals than on fish clientele. Juvenile bluestreak cleaners are seen to bite their clients more often than the adults within that region, thus changing the dynamic of the known mutualistic relationship. However, in regions where the bluestreak cleaners are solely dependent on clients' parasites, fish who have access to cleaning services have better body condition than those without cleaner access. In the Marsa Bareika of the Ras Mohamed Nature Reserve, Egypt, the bluestreak cleaner wrasse live in specific sectors of the shallow reefs and are shown to rely on ectoparasites from species such as the brown surgeonfish and white belly damselfish. In this region, fish that visit cleaner wrasses have lower antibody responses than those without cleaner access, suggesting that cleaner access may decrease the need for active immunity. <!-- not specific to this species ===Life history=== All cleaner wrasses start their lives as females. A group of six to eight cleaner wrasses contains only one male, as the rest are females or juveniles. When the male dies, the strongest female changes her sex, an occurrence known as sequential hermaphroditism.Cleaner wrasses sleep in crevices between rocks or corals, covered in a slime layer they secrete at dusk and which can be seen floating on the surface in the morning. Cleaner wrasses live for about four years, and can grow to up to four inches.

Cooperation
This food acquisition also serves to clean the "client" fish in a mutualistic relationship: both parties benefit from the interaction. This relationship requires trust between the related parties because the cleaner wrasse wants to eat the flesh and mucus of the client fish, since this would be of a greater short-term benefit to the cleaner wrasse. Engaging in this behavior is considered to be "cheating". Punishment by the client fish deters this behavior. After being bitten, the client will either chase or flee away from the cleaner wrasse. This punishment proves to be effective because cleaner wrasses are less likely to bite the client in future interactions. Cooperation increases in the presence of bystanders, especially those that are attractive food sources (large and highly parasitized). The cleaner wrasses were found to feed against their preferences and not cheat when doing so would allow them access to more future clients.

Competition and cheating
Competition and access to multiple partners leads to improved cleaning of clients by cleaner wrasses. When the client has the opportunity to switch cleaning partners, each interaction lasts longer. Thus there is a more extensive cleaning of the client. This does not mean that there is less cheating though. To limit the cheating of cleaner wrasses, a client with access to many partners may utilize many different strategies, such as punishment and pursuit. When cheated, the clients will aggressively pursue and chase the cleaner wrasses. Other clients will be able to see this chase and will know to avoid engaging with that specific cleaner wrasse in the future.

Punishment
To go along with the importance of attractive food sources, cleaner wrasses vary intensity of punishment of each other. Males punish females more extensively when similarly sized females cheat highly valued clients. Clients watch cleaning interactions between cleaner wrasses and other clients, so that they know which ones to avoid. Males and females clean in groups, so if one cheats the other pays the price as well. This is why males punish females through cheating in return, partner switching, or termination of partnership. The size of the female is important because punishment is passed down the dominance hierarchy, and there is little threat of retaliation by subordinates. The males are the most dominant and do not want females to overtake them to become males due to the hermaphroditic trait. Cheating by similarly sized females can lead to a decrease in size difference at which females change sex and become competitors to the males. This has been determined to be adaptive since females respond to become more cooperative after increased punishment. Punishment can be adjusted based on circumstances, and these subtleties have an important bearing on cooperative interaction. -->

Reproduction
Cleaner wrasse males defend specific living territories from other males in which they are able to have control over the females in those territories. When the dominant male no longer exists in that territory, one of the larger females is able to change sexes to take control over that territory.