Cleaner fish are fish that provide a service to other species by removing dead skin and ectoparasites. Although the animal being cleaned typically is another fish, it can also involve aquatic reptiles (sea turtles and marine iguana), mammals (manatees and whales) or octopuses. The cleaning symbiosis is an example of mutualism, an ecological interaction that benefits both parties involved. However, the cleaner fish may sometimes cheat and consume mucus or tissue, thus creating a form of parasitism. A wide variety of fish including wrasse, cichlids, catfish, pipefish, and gobies display cleaning behaviors. Similar behavior is found in other groups of animals, such as cleaner shrimps.
Cleaner fish advertise their services with conspicuous coloration, often displaying a brilliant blue stripe that spans the length of the body. This adaptation has evolved independently in different species of cleaner fish, making it an example of convergent evolution. Other species of fish, called mimics, imitate the behavior and phenotype of cleaner fish to gain access to client fish tissue. This is another example of convergent evolution.
The best known cleaner fish are the cleaner wrasses of the genus Labroides found on coral reefs in the Indian Ocean and Pacific Ocean. These small fish maintain so-called cleaning stations where other fish, known as hosts, congregate and perform specific movements to attract the attention of the cleaner fish. Remarkably, these small cleaner fish safely clean large predatory fish that would otherwise eat small fish such as these.
While they derive the majority of their nutrients by removing ectoparasites, cleaner fish also feed on the mucus and tissue of the client fish, as these food sources have greater nutritional value. There is however a risk of terminating the cleaning interaction if the cleaner is too aggressive, taking too much mucus and tissue. Because of this, cleaners seek a balance in feeding between ectoparasites and mucus or tissue.
Cleaning behaviors have been observed in a number of other fish groups. Neon gobies of the genera Gobiosoma and Elacatinus provide a cleaning service similar to the cleaner wrasses, though this time on reefs in the western Atlantic, providing a good example of convergent evolution. Unlike the cleaner wrasses, they also eat a variety of small animals as well being cleaner fish, and generally do well in aquaria. However, the Caribbean cleaning goby (Elacatinus evelynae) gladly eat scales and mucus from the host when the ectoparasites it normally feeds on are scarce, making the relationship somewhat less than mutually beneficial. The symbiosis does not break down because the abundance of these parasites varies significantly seasonally and spatially, and the overall benefit to the larger fish outweighs any cheating on the part of the smaller.
An interesting example of a cleaning symbiosis has been observed between two brackish water cichlids of the genus Etroplus from South Asia. The small species Etroplus maculatus is the cleaner fish, and the much larger Etroplus suratensis is the host that receives the cleaning service.
Cleaning has infrequently been observed in fresh waters compared to marine waters, but at least in part this is possibly related to fewer observers (such as divers) in the former habitat compared to the latter. One of the few known examples of cleaning is juvenile striped Raphael catfish cleaning the piscivorous Hoplias cf. malabaricus. In public aquariums, Synaptolaemus headstanders have been seen cleaning larger fish.
Mimic species have evolved body forms, patterns, and colors which imitate other species to gain a competitive advantage. One of the most studied examples of mimicry on coral reefs is the relationship between the aggressive mimic Plagiotremus rhinorhynchos (the bluestriped fangblenny) and the cleaner wrasse model Labroides dimidiatus. By appearing like L. dimidiatus, P. rhinorhynchos is able to approach and subsequently feed on the tissue and scales of client fish while posing as a cleaner.
The presence of the cleaner mimic, P. rhinorhynchos, has a negative impact on the foraging success of the cleaner model L. dimidiatus. P. rhinorhynchos feeds by eating the tissue and scales of client fish, making client fish much more cautious while at cleaning stations. More aggressive mimics have a greater negative impact on the foraging rate and success of the cleaner fish. When mimics appear in higher densities relative to cleaners, there is a significant decline in the success rate of the cleaner fish. The effects of the mimic/model ratio are susceptible to dilution, whereby an increase in client fish allows both the mimics and the models to have more access to clients, thus limiting the negative effects that mimics have on model foraging success.
Media related to Cleaner fish at Wikimedia CommonsAggressive mimicry
Aggressive mimicry is a form of mimicry in which predators, parasites or parasitoids share similar signals, using a harmless model, allowing them to avoid being correctly identified by their prey or host. Zoologists have repeatedly compared this strategy to a wolf in sheep's clothing. In its broadest sense, aggressive mimicry could include various types of exploitation, as when an orchid exploits a male insect by mimicking a sexually receptive female (see pseudocopulation), but will here be restricted to forms of exploitation involving feeding. An alternative term Peckhamian mimicry (after George and Elizabeth Peckham) has been suggested, but is seldom used. The metaphor of a wolf in sheep's clothing can be used as an analogy, but with the caveat that mimics are not intentionally deceiving their prey. For example, indigenous Australians who dress up as and imitate kangaroos when hunting would not be considered aggressive mimics, nor would a human angler, though they are undoubtedly practising self-decoration camouflage. Treated separately is molecular mimicry, which shares some similarity; for instance a virus may mimic the molecular properties of its host, allowing it access to its cells.
Aggressive mimicry is opposite in principle to defensive mimicry, where the mimic generally benefits from being treated as harmful. The mimic may resemble its own prey, or some other organism which is beneficial or at least not harmful to the prey. The model, i.e. the organism being 'imitated', may experience increased or reduced fitness, or may not be affected at all by the relationship. On the other hand, the signal receiver inevitably suffers from being tricked, as is the case in most mimicry complexes.
Aggressive mimicry often involves the predator employing signals which draw its potential prey towards it, a strategy which allows predators to simply sit and wait for prey to come to them. The promise of food or sex are most commonly used as lures. However, this need not be the case; as long as the predator's true identity is concealed, it may be able to approach prey more easily than would otherwise be the case. In terms of species involved, systems may be composed of two or three species; in two-species systems the signal receiver, or "dupe", is the model.
In terms of the visual dimension, the distinction between aggressive mimicry and camouflage is not always clear. Authors such as Wickler have emphasized the significance of the signal to its receiver as delineating mimicry from camouflage. However, it is not easy to assess how 'significant' a signal may be for the dupe, and the distinction between the two can thus be rather fuzzy. Mixed signals may be employed: aggressive mimics often have a specific part of the body sending a deceptive signal, with the rest being hidden or camouflaged.Bluehead wrasse
The bluehead wrasse or blue-headed wrasse (Thalassoma bifasciatum) is a species of saltwater fish in the wrasse family (Labridae) of order Perciformes native to the coral reefs of the tropical waters of the western Atlantic Ocean. Individuals are small (less than 110 mm standard length) and rarely live longer than two years. They form large schools over the reef and are important cleaner fish in the reefs they inhabit.Cleaner shrimp
Cleaner shrimp is a common name for a number of swimming decapod crustaceans, that clean other organisms of parasites. They belong to any of three families, Hippolytidae (including the Pacific cleaner shrimp, Lysmata amboinensis), Palaemonidae (including the spotted Periclimenes magnificus) , and Stenopodidae (including the banded coral shrimp, Stenopus hispidus) . The last of these families is more closely related to lobsters and crabs than it is to the remaining families. The term "cleaner shrimp" is sometimes used more specifically for the family Hippolytidae and the genus Lysmata.
Cleaner shrimp are so called because they exhibit a cleaning symbiosis with client fish where the shrimp clean parasites from the fish. The fish benefit by having parasites removed from them, and the shrimp gain the nutritional value of the parasites. The shrimp also eat the mucus and parasites around the wounds of injured fish, which reduces infections and helps healing. The action of cleansing further aids the health of client fish by reducing their stress levels. In many coral reefs, cleaner shrimp congregate at cleaning stations. In this behaviour cleaner shrimps are similar to cleaner fish, and sometimes may join with cleaner wrasse and other cleaner fish attending to client fish.
Shrimp of the genus Urocaridella are often cryptic or live in caves on the reef and are not associated commensally with other animals. These shrimp assemble around cleaning stations where up to 25 shrimp live in proximity. When a potential client fish swims close to a station with shrimp present, several shrimp perform a "rocking dance," a side-to-side movement. Frequency of rocking increases with hunger. This increase in frequency suggests competition between hungry and sated shrimp. To avoid competition with other cleaners during the day, the shrimp Urocaridella antonbruunii was observed cleaning a sleeping fish at night.Cleaner shrimps are often included in saltwater aquaria partly due to their cleansing function and partly due to their brightly colored appearance.Cleaning station
A cleaning station is a location where aquatic life congregate to be cleaned by smaller creatures. Such stations exist in both freshwater and marine environments, and are used by animals including fish, sea turtles and hippos.The cleaning process includes the removal of parasites from the animal's body (both externally and internally), and is performed by various smaller animals including cleaner shrimp and numerous species of cleaner fish, especially wrasses and gobies (Elacatinus spp.).
When the animal approaches a cleaning station, it will open its mouth wide or position its body in such a way as to signal that it needs cleaning. The cleaner fish will then remove and eat the parasites from the skin, even swimming into the mouth and gills of any fish being cleaned. This is a form of cleaning symbiosis.
Cleaning stations may be associated with coral reefs, located either on top of a coral head or in a slot between two outcroppings. Other cleaning stations may be located under large clumps of floating seaweed or at an accepted point in a river or lagoon.
Some species of combtooth blenny, most notably the false cleanerfish, mimic the appearance and behaviour of cleaners, then tear away scales or flesh when suitably close to the victim.Cleaning symbiosis
Cleaning symbiosis is a mutually beneficial association between individuals of two species, where one (the cleaner) removes and eats parasites and other materials from the surface of the other (the client). Cleaning symbiosis is well-known among marine fish, where some small species of cleaner fish, notably wrasses but also species in other genera, are specialised to feed almost exclusively by cleaning larger fish and other marine animals. Other cleaning symbioses exist between birds and mammals, and in other groups.
Cleaning behaviour was first described by the Greek historian Herodotus in about 420 BC, though his example (birds serving crocodiles) appears to occur only rarely.
The role of cleaning symbioses has been debated by biologists for over thirty years. Some believe that cleaning represents selfless co-operation, essentially pure mutualism, increasing the fitness of both individuals. Others such as Robert Trivers hold that it illustrates mutual selfishness, reciprocal altruism. Others again believe that cleaning behaviour is simply one-sided exploitation, a form of parasitism.
Cheating, where either a cleaner sometimes harms its client, or a predatory species mimics a cleaner, also occurs. Predatory cheating is analogous to Batesian mimicry, as where a harmless hoverfly mimics a stinging wasp, though with the tables turned. Some genuine cleaner fish, such as gobies and wrasse, have the same colours and patterns, in an example of convergent evolution. Mutual resemblance among cleaner fish is analogous to Müllerian mimicry, as where stinging bees and wasps mimic each other.Cortez rainbow wrasse
The Cortez rainbow wrasse (Thalassoma lucasanum) is a species of wrasse native to the eastern Pacific Ocean from Baja California to Peru, as well as around the Galapagos Islands. It is a reef inhabitant, occurring in small schools from the surface to depths of 64 m (210 ft), though rarely deeper than 25 m (82 ft) or shallower than 2 m (6.6 ft). It is generally very common. It can also be found in the aquarium trade. This species can reach 15 cm (5.9 in) in total length. It feeds on small organisms such as crustaceans, plankton and fish eggs, and the young are cleaner fish.Crimson cleaner fish
Suezichthys aylingi, the Crimson cleaner fish, or butcher's dick in Australia, is a species of wrasse native to the southwestern Pacific Ocean around Australia and New Zealand. This species inhabits patches of sand on reefs at depths of from 6 to 100 metres (20 to 328 ft). It is a cleaner fish. Males of this species can reach a length of 11.7 centimetres (4.6 in) SL while females only reach 8.6 centimetres (3.4 in).Elacatinus oceanops
Elacatinus oceanops, the neon goby, is a species of goby native to waters of the Atlantic and Gulf coast of North America from Florida to Belize. This cleaner fish can be found on coral heads at depths from 1 to 45 m (3.3 to 147.6 ft). This species grows to a total length of 5 cm (2.0 in). This species can also be found in the aquarium trade.Fish disease and parasites
Like humans and other animals, fish suffer from diseases and parasites. Fish defences against disease are specific and non-specific. Non-specific defences include skin and scales, as well as the mucus layer secreted by the epidermis that traps microorganisms and inhibits their growth. If pathogens breach these defences, fish can develop inflammatory responses that increase the flow of blood to infected areas and deliver white blood cells that attempt to destroy the pathogens.
Specific defences are specialised responses to particular pathogens recognised by the fish's body, that is adaptative immune responses. In recent years, vaccines have become widely used in aquaculture and ornamental fish, for example vaccines for furunculosis in farmed salmon and koi herpes virus in koi.Some commercially important fish diseases are VHS, ich and whirling disease.Fish intelligence
Fish intelligence is "...the resultant of the process of acquiring, storing in memory, retrieving, combining, comparing, and using in new contexts information and conceptual skills" as it applies to fish.
According to Culum Brown from Macquarie University, "Fish are more intelligent than they appear. In many areas, such as memory, their cognitive powers match or exceed those of ‘higher’ vertebrates including non-human primates."Fish hold records for the relative brain weights of vertebrates. Most vertebrate species have similar brain-to-body mass ratios. The deep sea bathypelagic bony-eared assfish, has the smallest ratio of all known vertebrates. At the other extreme, the electrogenic elephantnose fish, an African freshwater fish, has one of the largest brain-to-body weight ratios of all known vertebrates (slightly higher than humans) and the highest brain-to-body oxygen consumption ratio of all known vertebrates (three times that for humans).Four-line wrasse
The four-line wrasse, Larabicus quadrilineatus, is a species of wrasse native to the Red Sea and the Gulf of Aden. It can be found on coral reefs at depths from the surface to 15 m (49 ft). Juveniles are cleaner fish, while the adults feed on coral polyps. This species grows to 11.5 cm (4.5 in) in total length. This species is the only known member of its genus.Hawaiian cleaner wrasse
The Hawaiian cleaner wrasse or golden cleaner wrasse (Labroides phthirophagus), is a species of wrasse (genus Labroides) found in the waters surrounding the Hawaiian Islands. The fish is endemic to Hawaii. These cleaner fish inhabit coral reefs, setting up a territory referred to as a cleaning station. They obtain a diet of small crustacean parasites by removing them from other reef fish in a cleaning symbiosis.Johnrandallia nigrirostris
The blacknosed butterflyfish or barberfish (Johnrandallia nigrirostris) (from the Spanish names, El Barbero or Mariposa Barbero, "the barber" or "butterfly barber"), is a species of fish in the family Chaetodontidae, the butterfly fishes. It is found in the East Pacific, specifically around the Galapogas Islands and in the Sea of Cortez, and it sometimes acts as a cleaner fish. It is the only member of the genus Johnrandallia, named after the ichthyologist John E. Randall, but in the past it was commonly placed in Chaetodon.Kelp perch
Brachyistius frenatus, the Kelp perch, is a species of surfperch native to the eastern Pacific Ocean from British Columbia, Canada to Baja California, Mexico where it is found in kelp forests down to a depth of about 30 metres (98 ft). This fish is also known to be a cleaner fish. This species can reach a length of 22 centimetres (8.7 in) TL. It can also be found on display at public aquariums.Labroides
Labroides is a genus of wrasses native to the Indian and Pacific Oceans. This genus is collectively known as cleaner wrasses, and its species are cleaner fish.Noronha wrasse
The Noronha wrasse, Thalassoma norohanum, is a species of wrasse native to the western Atlantic Ocean off the coast of Brazil and nearby islands, where it inhabits coral reefs from the surface to 60 m (200 ft) deep, though mostly much shallower, between 2 and 5 m (6.6 and 16.4 ft). Younger individuals act as cleaner fish. This species can reach 13.3 cm (5.2 in) in standard length. It can also be found in the aquarium trade.Reciprocal altruism
In evolutionary biology, reciprocal altruism is a behaviour whereby an organism acts in a manner that temporarily reduces its fitness while increasing another organism's fitness, with the expectation that the other organism will act in a similar manner at a later time. The concept was initially developed by Robert Trivers to explain the evolution of cooperation as instances of mutually altruistic acts. The concept is close to the strategy of "tit for tat" used in game theory.Wrasse
The wrasses are a family, Labridae, of marine fish, many of which are brightly colored. The family is large and diverse, with over 600 species in 81 genera, which are divided into 9 subgroups or tribes.
They are typically small fish, most of them less than 20 cm (7.9 in) long, although the largest, the humphead wrasse, can measure up to 2.5 m (8.2 ft). They are efficient carnivores, feeding on a wide range of small invertebrates. Many smaller wrasses follow the feeding trails of larger fish, picking up invertebrates disturbed by their passing. Juveniles of some representatives of the genera Bodianus, Epibulus, Cirrhilabrus, Oxycheilinus, and Paracheilinus hide among the tentacles of the free-living mushroom coral Heliofungia actiniformis.The word "wrasse" comes from the Cornish word wragh, a lenited form of gwragh, meaning an old woman or hag, via Cornish dialect wrath. It is related to the Welsh gwrach and Breton gwrac'h.Yellowtail tubelip
The yellowtail tubelip , Diproctacanthus xanthurus, is a species of wrasse native to coral reefs of the western Pacific Ocean. It can be found at depths from 3 to 25 m (9.8 to 82.0 ft). The juveniles act as cleaner fish, while the adults primarily prey on coral polyps. This species grows to a total length of 10 cm (3.9 in). It can be found in the aquarium trade. This species is the only known member of its genus.