Cleaner fish
Cleaner fish are
There are two types of cleaner fish, obligate full time cleaners and facultative part time cleaners[1] where different strategies occur based on resources and local abundance of fish.[1] Cleaning behaviour takes place in pelagic waters as well as designated locations called cleaner stations.[8] Cleaner fish interaction durations and memories of reoccurring clients are influenced by the neuroendocrine system of the fish, involving hormones arginine vasotocin, Isotocin and serotonin.[3]
Conspicuous coloration is a method used by some cleaner fish, where they often display a brilliant blue stripe that spans the length of the body.[9] Other species of fish, called mimics, imitate the behavior and phenotype of cleaner fish to gain access to client fish tissue.
The specialized feeding behaviour of cleaner fish has become a valuable resource in
Diversity and examples
Marine fish
The following is a selection of few of the many marine cleaner species.
Commonly studied cleaner fish are the cleaner wrasse of the genus Labroides found on coral reefs in the Indian Ocean and Pacific Ocean.[8]
Neon gobies of the genera Gobiosoma and Elacatinus provide a cleaning service similar to the cleaner wrasse, though this time on reefs in the Western Atlantic, providing a good example of convergent evolution[12] of the cleaning behaviour.
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A disruptively patterned white-spotted puffer being cleaned by a conspicuously coloured Hawaiian cleaner wrasse
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Lumpfish (Cyclopterus lumpus), a cleaner fish employed in salmon farming in Atlantic Canada, Scotland, Iceland and Norway[14]
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A neon goby from the Western Atlantic
Brackish water fish
Freshwater fish
Cleaning has been observed infrequently in fresh waters compared to marine waters. This is possibly related to fewer observers (such as divers) in freshwater compared to saltwater.[16] One of the few known examples of freshwater cleaning is juvenile striped Raphael catfish cleaning the piscivorous Hoplias cf. malabaricus. In public aquariums, Synaptolaemus headstanders have been seen cleaning larger fish.[17][18]
Mechanisms
Facultative cleaner fish
A facultative cleaner fish does not rely solely on specialized cleaning behaviour for nutritious food.
Using the example of the blue wrasse from Caribbean waters, their alternative feeding strategy is described as being a generalist
Obligate cleaner fish
An obligate cleaner fish relies solely on specialized cleaning behaviour for its food.[2] Therefore, obligate cleaners have a higher output of cleaning on a wider range of parasites in comparison to facultative fish. To maximize nutrient consumption, obligate cleaners utilize a higher proportion of cleaning stations.[1] Obligate cleaner fish may also be divided by stationary and wandering. These life history choice are made based on the amount of interspecific competition from other obligate cleaners in the area.[19] An example of an obligate cleaner is the shark nose goby (Elacatinus evelynae) in the Caribbean Reef, where it has been observed to perform up to 110 cleanings per day.[1]
Cleaner stations
Interactions are begun by the client and ended by the cleaner, implying that the client is seeking out the service where the cleaner has control.[2]
Cheating
Cheating parasitism occurs when the cleaner eats mucus or healthy tissue from the client. This can be harmful to the client as mucus is essential to prevent UV damage, and open wounds can increase the risk of infection.
Memory
Cleaner fish (especially facultative cleaners) assess the value of possible clients when deciding whether to invest in a client or cheat and eat mucus or tissue.[1][3] Observations of cleaner and client interactions have found that cleaners may provide the client with tactile stimulation as a way to establish a relationship and gain the client's 'trust'. This interaction costs the cleaner as it is time not spent feeding.[3] This physical interaction demonstrates a cleaner fish's tradeoff. The cleaner minimizes feeding time to establish a memorable relationship with the client that also contributes to conflict management with a possibly predatory client.[3]
Neurobiology
The cleaner fish neuroendocrine system has been studied specifically in reference to arginine vasotocin (AVT) and Isotocin. These are fish-specific hormones that are analogous to human hormones involved in sociality.[3] In laboratory experiments, during conditions of low AVT, cleaners are more engaged in interspecific interactions. High AVT conditions tend to show high client interactions but more instances of cheating. This implies that AVT expression acts as a switch for cleaner fish feeding behaviour, showing less client interactions (but more honest cleaning) or increased client interactions (with less honest cleaning).[3] It has also been observed that obligate cleaners have higher overall brain activity, and specifically in the cerebellum, likely related to the movements involved in cleaning.[3]
Serotonin has also been noted to influence cleaning behaviour. High serotonin increases motivation to interact with clients, and a lack of serotonin decreases client interaction and slows learning.[3]
Mimicry
Mimic species have evolved body forms, patterns, and colors which imitate other species to gain a competitive advantage.
The presence of the cleaner mimic, P. rhinorhynchos, reduces the foraging success of the cleaner model L. dimidiatus.[22] 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.[22] 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.[23][24]
Similar species also include Plagiotremus tapeinosoma (the Mimic blenny), Aspidontus.
Implications
Salmonid aquaculture
Methods
Cleaner fish are commercially cultured and introduced into salmonid sea cages. Salmon and lumpfish are able to coexist, where the lumpfish spend a certain amount of time foraging for supplemented food and only a portion of their time delousing salmon. With significant ratios of cleaner to client, the efforts are sufficient to minimize louse outbreaks.[13][11] Sea cages are designed with additional substrate for lumpfish to attach to during periods of inactivity to minimize stress levels in the cleaner fish and maximize delousing abilities.[13]
Challenges of using cleaner fish
North Atlantic Aquaculture facilities use facultative cleaner fish (
Minimizing disease in commercial lumpfish stocks is critical for the continuation of their usage in aquaculture. Vaccine development for the lumpfish is a current area of research as lumpfish demand is increasing in the aquaculture industry.[13] In an effort to minimize disease in the cleaner fish, commercial lumpfish stocks are supplemented with wild individuals during the breeding season to minimize inbreeding depression. The lumpfish genome has not yet been fully sequenced so subtle details between populations are not yet appreciated.[13]
Another consideration in using cleaner fish in aquaculture is minimizing escapees from sea cages. If escaped cleaner fish spawn with natural populations in the environment it may decrease the wild fishes' natural survival abilities.[13]
Environment
Cleaner fish have taken over lice-reduction strategies, which were based upon chemical delousers in the past. This decreases the amount of effluent waste affecting the surrounding wild habitats in outdoor aquaculture.[11] Introducing cleaner fish into salmonid aquaculture cages has also been found to be less stressful on salmonids than medical intervention for sea lice outbreaks.[13]
Cleaner fish in the wild contribute to the overall health of aquatic communities by reducing morphological and physiological injuries by parasites to other species of fish. Maintenance of these populations of fish help the complex web of interactions remain stable.[2]
Economic
Sea lice outbreaks are detrimental to the survival of cultured salmonids and cause the majority of revenue loss in the aquaculture business. By employing the cleaner fish instead of medical intervention for sea louse management, aquaculture farmers save money.[13]
See also
- Doctor fish, fish that provide a cleaning service to humans
- Reciprocal altruism
- Social grooming, cleaning services offered between members of the same species
References
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- ^ OCLC 36051279.
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- ^ a b "Cleaner fish – what do they do?". Lochduart. 2017-06-08. Retrieved 2019-10-27.
- ^ S2CID 51871138.
- OCLC 38168280.
- ^ ISSN 1753-5131.
- ^ "Cleaner fish – what do they do?". Lochduart. 2017-06-08. Retrieved 2019-10-28.
- JSTOR 1442742.
- ^ Carvalho, L.N (2007). "Natural history of Amazon fishes". In Encyclopedia of Life Support Systems (ed.). Tropical Biology and Natural Resources Theme. 1. Oxford: Eolss Publishers. pp. 1–24.
- ^ "Broadband red headstander". Den Blå Planet. 2016-10-03. Retrieved 2019-10-27.
- ^ "Broadband red headstander". National Aquarium Denmark. 2016-10-03. Retrieved 18 August 2018.
- S2CID 17321980.
- PMID 17148155.
- ^ PMID 17986437.
- ^ PMID 21865244.
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- ^ "Lumpfish: Emerging species profile list. DFO" (PDF).
- ^ "Labrus bergylta : Ballan Wrasse | NBN Atlas". species.nbnatlas.org. Retrieved 2019-10-28.
External links
Media related to Cleaner fish at Wikimedia Commons