Strategic adjustment of service quality to client identity in the cleaner shrimp, <i>Periclimenes longicarpus</i>

Cleaning mutualism, in which cleaning organisms remove ectoparasites from cooperating ‘clients’, is widespread among marine animals. Until now, research has focused on fishes as cleaners, whereas cleaner shrimps have received little attention. The aim of this study was to investigate the cleaning behaviour of the cleaner shrimp, <i>Periclimenes longicarpus</i>, and to compare the results directly to data on the sympatric and well-studied cleaner wrasse, <i>Labroides dimidiatus</i>. We first compared the time spent cleaning and client diversity as indicators of the potential importance of the cleaner shrimp to client health and found strong similarities between shrimp and wrasse. We further looked at three correlates of service quality: duration of interactions, tactile stimulation of clients, and jolt rates as correlates of mucus feeding (=cheating). We specifically predicted that shrimps would cheat clients less frequently than the wrasses because they should be more vulnerable to aggressive responses by clients. Although the results partly support our hypothesis, they also suggest that both species strategically adjust cheating rates according to risk, as predatory clients jolted less frequently than nonpredatory clients. In conclusion, the results suggest that the shrimps play an important role in client health but that nonpredatory clients have to control the shrimps' behaviour to receive a good service.