Bshary, Redouan

2008, Soares, Marta C., Bshary, Redouan, Côté, Isabelle M.

Cleaning fish mutualisms appear to be good examples of biological markets. Two classes of traders exist: cleaner fish and their fish clients, each of which supplies a commodity required by the other (ectoparasite removal and a meal, respectively). However, clients are not all treated similarly by cleaners. There is evidence that clients with choice options (with potential access to more than one cleaner) have priority of access over clients without choice options. Market theory predicts that client value (i.e. ectoparasite load) should also influence cleaning service quality. We examined the relative roles of client choice options and client value in determining the duration of cleaning interactions between bluestreak cleaner wrasse, Labroides dimidiatus, and their clients across three geographically distant sites. We found a lack of covariation between client choice options and gnathiid ectoparasite loads. Geographical differences in gnathiid availability altered the importance of client gnathiid load as a determinant of client inspection duration. As predicted, clients with both choice options and high gnathiid loads were inspected for longer, but this was observed only in an area with a relatively high incidence of parasitism. These correlational results suggest that the importance of client choice for aspects of cleaner fish service quality may be modulated by parasite availability.

2005, Bshary, Redouan, Grutter, Alexandra S.

What are the mechanisms that prevent partners from cheating in potentially cooperative interactions between unrelated individuals? The cleaner fish Labroides dimidiatus and client reef fish both benefit from an interaction as long as the cleaner eats ectoparasites. However, the cleaner fish prefers some client mucus, which constitutes cheating. Field observations suggested that clients control such cheating by using punishment (chasing the cleaner) or by switching partners (fleeing from the cleaner). Here, we tested experimentally whether such client behaviours result in cooperative cleaner fish. Cleaners were allowed to feed from Plexiglas plates containing prawn items and fish flake items. A lever attached to the plates allowed us to mimic the behaviours of clients. As cleaners showed a strong preference for prawn over flakes, we taught them that eating their preferred food would cause the plate to either chase them or to flee, while feeding on flakes had no negative consequences. We found a significant shift in cleaner fish foraging behaviour towards flake feeding after six learning trials. As punishment and terminating an interaction resulted in the cleaners feeding against their preferences in our experiment, we propose that the same behaviours in clients improve the service quality of cleaners under natural conditions.