Cleaning interactions at the only atoll in the South Atlantic

In marine ecosystems, cleaning is a mutualistic relationship in which so-called cleaners remove ectoparasites, diseased tissue, or mucus from the body of their clients, and thus help to maintain a healthy reef community. In spite of its importance in many marine habitats, this interaction remains poorly understood, particularly at oceanic islands. Here, we present the first comprehensive study of cleaning interactions in a reef fish assemblage at Rocas, the only atoll in the South Atlantic. We recorded 318 cleaning events, in which six fish species, including two endemic ones, and two shrimp species acted as cleaners. The clients serviced by these cleaners were 21 bony fish species, one shark and one sea turtle. The cleaner wrasse Thalassoma noronhanum and the cleaner goby Elacatinus phthirophagus were the cleaners with the greatest number of events and species richness of clients. Additionally, 82% of clients in the cleaning events were non-piscivores, and the abundance of both cleaners and clients positively influenced the number of cleaning events (R-2 = 0.4; p < 0.001). Our results indicate that Rocas atoll has a high species richness of cleaner species despite its small size and highlight the importance of studies of cleaning symbiosis, even in isolated places with low species richness, for a better comprehension of this association in reefs.