Cleaner fish coloration does not always reduce predation risk: testing the effect of protective mimicry in the false cleanerfish, Aspidontus taeniatus

Cleaning symbiosis of the bluestreak cleaner wrasse, Labroides dimidiatus (Labridae), is a well-known example of mutualism in coral reefs. The cleaner wrasse is characterized by its bluish body colour with black stripes, and the false cleanerfish, Aspidontus taeniatus (Blenniidae), mimics those characteristics precisely. Cleaner fish mimicry is believed to evolve as an aggressive mimicry to bite the fins of deceived fishes; however, protective mimicry to reduce predation risk has not been examined sufficiently. Here, we tested the effect of protective mimicry through field observations and aquarium experiments. Field observations revealed that false cleanerfish were occasionally attacked by piscivorous lizardfishes (Synodontidae). In the aquarium experiments, ambushing predators, the honeycomb grouper, Epinephelus merra (Serranidae), which did not show predatory behaviour to false cleanerfish in the field, attacked the cleaner wrasse (model), the false cleanerfish (mimic), and the lance blenny, Aspidontus dussumieri (non-mimic). When a shelter was provided in the tank, the false cleanerfish and the lance blenny immediately hid inside the shelter for a considerable duration to escape from the predator. These results suggest that cleaner fish coloration does not always decrease predation risks, and our conclusions support the possibility that this mimicry evolved primarily as aggressive mimicry.