Using the marine cleaning mutualisms to study the physiological bases of cooperative and deceptive behaviour

Cleaner fish inspect the surface, gills and sometimes the mouth of so called ‘client’ reef fish, eating ectoparasites, mucus, scales and dead or infected tissue. Individuals of the best studied species, the Indo-Pacific bluestreak cleaner wrasse Labroides dimidiatus, may engage in as many as 2000 such interactions per day, and individual clients often visit cleaners several times during the same period, the highest recorded number of visits exceeding 100. While there is evidence that both cleaners and clients typically gain from their encounters, there are several conflicts of interest that lead to sophisticated behavioural strategies: predatory clients may try to eat cleaners, cleaners prefer the protective mucus layer of clients over ectoparasites, and sometimes two or more clients simultaneously seek the service of the same cleaner. In addition, cleaners are known to recognize individual clients, to distinguish between client categories (predators – non predators, residents – visitors), to reconcile and manipulate client decisions by providing a form of tactile stimulation with their pelvic fins, to adjust their service quality to the presence or absence of potential clients, and to use predators as social tools to stop other clients from punishing after a cheat. During this talk I will focus on the methodology applied to collect empirical data on these systems, as to answer both functional and mechanistic questions.