Biological markets: The quality of service of cleaner fish depends on supply and demand

Written by Thomas Hesselberg

Friday, 11 July 2008

Two small bluestreak cleaner wrasses cleaning a potato cod at a cleaning stations. Courtesy of Wikimedia Commons (taken by Richard Ling).

A new study published in Animal Behaviour shows that economical principles are also operating in the natural world. The cleaner fish spend longer time on cleaning their bigger client fish, when these can choose between several cleaner fish.

The fields of evolutionary ecology/behaviour and economics use more and more of each others methodology. Many animal interactions and economical transactions can be described with the same mathematical models. A research team comprising biologists from universities in the United Kingdom, Switzerland and Canada has found further similarities in a study of the behaviour of the bluestreak cleaner wrasse (Labroides dimidiatus) in its response to competition and clients.

The bluestreak cleaner wrasse is found on coral reefs in the Indian Ocean, where it feeds on parasites and dead skin on larger fish in a mutualistic relationship, which offers food for the cleaner and health benefits for the client. The relationship is so advanced that specific cleaning stations associated with distinct coral features exist whereto the larger client fish (such as parrot fish and goat fish) swim and orderly queue to get cleaned.

The research team conducted behavioural observations during dives to cleaning stations in different geographical regions. Individuals of the species of client fish observed were then caught to count the average number of ectoparasites.

The results showed that in some regions with higher average ectoparasite loads, the cleaner fish, not surprisingly, spend longer times on client fish who had many parasites, but more surprisingly also spend longer time on client fish, which had a choice of other nearby cleaning stations. No such relationships were found in regions with a low average parasite load.

In conclusion, it seems like the quality of service at a given cleaning station depends on the proximity of other cleaning stations (supply) and on the average number of parasites on clients (the general necessity to be cleaned or demand).

Source
Soares, M. C., Bshary, R. and Cote, I. M. (2008). Does cleaner fish service quality depend on client value or choice options? Animal Behaviour, 76, 123-130.

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