Filling an empty role: first report of cleaning by pygmy angelfishes (Centropyge, Pomacanthidae)

Cleaner fishes remove ectoparasites, mucus and dead tissues from other ‘client’ organisms. These mutu­ alistic interactions provide benefits for the ‘clients’ and, on a larger scale, maintain healthy reef ecosystems. Here, we report two species of angelfishes, Centropyge bicolor and C. tibicen, acting as cleaners of the blue tang Paracanthurus hepatus in an aquarium. This observation is the first time that pygmy angelfishes are recorded cleaning in any en vironment. This novel cleaning ob­ servation raises ques tions on the ecosystem role of cleaner fishes and which biological traits facilitate cleaning.