Symbiosis is a term used in biology. We use the following definition: the long-term relationship between two or more organisms, whereby the relationship is beneficial—or even necessary—for at least one of the organisms. Our eco-displays contain many examples of symbiosis. A symbiosis can involve different animal species or, for example, one animal species and one plant species. It is a fascinating phenomenon that beautifully illustrates the complexity and dynamics of ecosystems. All animal and plant species maintain various relationships with other organisms within an ecosystem. This time: the bluestreak cleaner wrasse and its host.
The bluestreak cleaner wrasse feeds on excess slimes, dead skin, dead scales and skin parasites of various larger types of fish. The larger fish generally enjoy being cleaned, and there are often several fish in the immediate vicinity awaiting their turn. The bluestreak cleaner wrasse usually hangs around fixed spots on the reef, called cleaning stations. They often work in pairs, but not always. The larger fish recognise the bluestreak cleaner wrasse by its colours and shape. Because they do such a nice and pleasant job, the bigger fish usually leave the bluestreak cleaner wrasse alone, saving them from ending up as snacks.
The advantages of this symbiosis are quite clear: the bluestreak cleaner wrasse is assured of food and is relatively well protected from potential enemies thanks to its cleaning activities, which is also recognised as such as the host gets rid of annoying, irritating skin parasites.
The larger fish even allow the bluestreak cleaner wrasse clean sensitive areas such as the gills. Not many can go near a moray eel's teeth without being worried! However, excess slimes, dead skin, scales, and skin parasites are not very nutritious. Sometimes, the bluestreak cleaner wrasse simply cannot resist the temptation and takes too big a bite on purpose, biting off a piece of the gill, for example. Naturally, this frightens the larger fish, and it usually swims away immediately and does not return. The other fish patiently awaiting their turn often swim away as well because they don't want a painful cleaning either!
It is a rather precarious balance: if a bluestreak cleaner wrasse never takes a bite from a larger fish, it is not doing itself justice. After all, there are far more calories in a bite from a victim than in dead material or skin parasites. But if the bluestreak cleaner wrasse takes a bite too often, it will soon lose all its "customers". In other words, if the bluestreak cleaner wrasse cheats too often, it will "lose its good name", as it were. Fish may have rather small brains, but they are by no means stupid. A fish that has been bitten by a bluestreak cleaner wrasse will continue to avoid cleaning visits for the time being.
