text: cleaning symbiosis cleaning symbiosis is a mutually beneficial association ( symbiosis ) between 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 . 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 mullerian mimicry , as where stinging bees and wasps mimic each other . history in his histories ( book ii ) , the ancient greek historian herodotus wrote : as [ the crocodile ] lives chiefly in the river , it has the inside of its mouth constantly covered with leeches ; hence it happens that , while all the other birds and beasts avoid it , with the trochilus it lives at peace , since it owes much to that bird : for the crocodile , when he leaves the water and comes out upon the land , is in the habit of lying with his mouth wide open , facing the western breeze : at such times the trochilus goes into his mouth and devours the leeches . this benefits the crocodile , who is pleased , and takes care not to hurt the trochilus . herodotus thus claimed ( circa 440 bc ) that nile crocodiles had what would now be called a cleaning symbiosis with the bird he called the trochilus , possibly a sandpiper ; but while he was right about the existence of cleaning symbioses , there is little evidence for it in crocodiles . in 1906 henry quoted john mason cook , son of travel agent thomas cook , as reporting from egypt that he had seen some spur - winged plovers approach a crocodile , which opened its jaws for them : mr. j. m. cook , of the celebrated tourist agency , when in egypt in 1876 , " watched one of these birds , and saw it deliberately go up to a crocodile , apparently asleep , which opened its jaws . the bird hopped in , and the crocodile closed its in what appeared to be a very short time , probably not more than a minute or two , the crocodile opened its jaws , and we saw the bird go down to the water 's edge . " there were several of these birds about , and mr. cook shot two of them , which dr. sclater identified as spur - winged plovers ; so that the question as to what bird enters the mouth of the crocodile is now set at rest . macfarland and reeder , reviewing the evidence , found that extensive observations of nile crocodiles in regular or occasional association with various species of potential cleaners ( e.g. plovers , sandpipers , water ) ... have resulted in only a few reports of sandpipers removing leeches from the mouth and gular scutes and snapping at insects along the reptile 's body . a disputed relationship cleaning symbiosis is a relationship between a pair of animals of different species , involving the removal and subsequent ingestion of ectoparasites , diseased and injured tissue , and unwanted food items from the surface of the host organism ( the client ) by the cleaning organism ( the cleaner ) . its status has been debated by biologists , with viewpoints ranging from pure mutualism through to a form of exploitative parasitism by the cleaner . marine biologist alexandra grutter explains : cleaning associations involve cleaner organisms that remove ectoparasites and other material , such as mucus , scales and skin , from the body surfaces of other apparently co - operating animals . the latter are often referred to as hosts , customers , or clients . cleaning behaviour is one of the most highly developed inter - specific communication systems known , with clients striking elaborate postures which have generally been assumed to make ectoparasites more accessible to cleaners . co - operation grutter and her colleague robert poulin , reviewing over thirty years of debate by biologists on cleaning symbioses , argue that " cleaning symbioses may not be mutualistic associations but rather one - sided exploitation " . they quote , for example , c. limbaugh as writing in 1961 : " from the standpoint of the philosopher of biology , the extent of cleaning behavior in the ocean emphasizes the role of co - operation in nature as opposed to the tooth - and - claw struggle for existence " . mutual selfishness in 1971 , mathematical biologist robert trivers wrote more carefully " cleaner organisms and their hosts meet the preconditions for the evolution of reciprocally altruistic behavior . the host 's altruism is to be explained as benefiting him because of the advantage of being able quickly and repeatedly to return to the same cleaner " ( i.e. mutual selfishness ) . one - sided exploitation by 1987 g. s. losey wrote less optimistically " cleaners are nothing but very clever behavioral parasites ... that have taken advantage of the rewarding aspects of tactile stimulation , found in nearly all vertebrates . " poulin and grutter remark that " over the last few decades , ... the opinion of scientists regarding cleaning symbioses has changed , from selfless cooperation , to a mutually beneficial interaction , and finally to a one - sided exploitation . " biological range cleaning symbiosis is known from several groups of animals both in the sea and on land ( see table ) . cleaners include fish , shrimps and birds ; clients include a much wider range of fish , marine reptiles including turtles and iguanas , octopus , whales , and terrestrial mammals . cleaning symbioses with reptile clients include fish cleaning the teeth of american crocodiles ( crocodylus acutus ) , geckos eating mosquitoes on aldabra giant tortoises ( geochelone gigantea ) and scarlet crabs ( ) , and three species of galapagos finches removing ticks from marine iguanas ( cristatus ) . the best known cleaning symbioses are among marine fishes , where several species of small fish , notably of wrasse , are specialised in colour , pattern and behaviour as cleaners , providing a cleaning and ectoparasite removal service to larger , often predatory fish . cleaner species , as shown in the table , vary widely in their degree of dependence on their clients . some are essentially pure obligate symbionts like the cleaner wrasse ; some are opportunistic or facultative symbionts , like the orange or some cleaner shrimps ; and some , like the oxpeckers , combine a little eating of parasites ( beneficial to client ) with taking of blood ( harmful to client ) , their favoured food . mimicry among cleaner fish mutual mimicry among cleaner fish many cleaner fish in different families , such as the caribbean neon goby ( elacatinus ) and the cleaner wrasse ( labroides dimidiatus ) , share the distinctive combination of a long narrow body , a longitudinal stripe , a blue colour , and small size . " convergent signalling among cleaners , using size , stripes and colour , should facilitate their recognition by fish clients . " this is analogous to mullerian mimicry where genuinely aposematic species ( such as wasps ) mimic each other 's warning colours . aggressive mimicry of blennies to cleaner fish the sabre - toothed blenny ( taeniatus ) is a predatory blenny , an aggressive mimic which accurately resembles the bluestreak cleaner wrasse , not only in colour and pattern , but also in the ritualised dance the cleaner wrasse makes when potential client fish swim nearby . however , instead of providing the cleaning service that it signals , it bites off pieces of healthy skin , scales and mucus from the host and then swims rapidly away to safety . the effect of aggressive mimicry in a cleaning symbiosis is analogous to batesian mimicry , where a harmless " edible mimetic species copies the warning signal of a noxious , aposematic model species , thereby gaining protection from predators " . as in batesian mimicry , the rate of successful attacks on cleaning clients by the ( ) , which like the sabre - toothed blenny mimic the bluestreak cleaner wrasse ( labroides dimidiatus ) , is frequency - dependent , meaning that the mimicry is more effective when the cheating is rare compared to the cleaner wrasse . the difference , however , is that the aggressive mimic is inserting itself into a co - operative relationship ( between cleaner and client ) , whereas " batesian mimics insert themselves into an antagonistic predator – prey interaction ( where the models are the unpalatable prey ) . 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