Low Ectoparasite Loads and Interactions With Cleaner Fish Among Amphiprion Anemonefish

ABSTRACT Interactions between ectoparasites, reef fishes and cleaner species are well documented; however, anemonefishes ( Amphiprioninae ) have been largely overlooked in this context. A hypothesis proposed as early as 1869 suggests that anemonefishes may experience reduced ectoparasite loads due to their symbiotic association with venomous host sea anemones; however quantitative field data are scarce. In this study, we provide a natural history account of ectoparasite loads and daytime cleaner wrasse interactions with anemonefishes. We quantified ectoparasites on wild Amphiprion ocellaris associated with Heteractis magnifica at a reef in Malaysia and conducted in situ observations of cleaner wrasse ( Labroides dimidiatus ) at cleaning stations and host anemone sites in Malaysia and the Maldives. Of the A. ocellaris sampled in Malaysia, 66.1% had no observable ectoparasites, and mean parasite load was low (0.6 ± 1.1, and larger, dominant females harboured more ectoparasites than smaller individuals). Across 23 h of daytime observations at 22 cleaning stations and 21 host anemone sites, we recorded 1657 cleaning interactions involving 54 fish species from 21 families; however, none involved anemonefishes. Rare cleaner wrasse approaches to anemonefishes were observed, but interactions were brief, and cleaners were consistently rejected. Our observations show that at our study reefs, anemonefishes do not use cleaner wrasse stations during daylight, and ectoparasite loads are typically low. We propose that association with host sea anemones, intrinsic defences, reduced parasite exposure and alternative cleaning pathways (e.g., nocturnal or shrimp‐mediated cleaning) are candidate mechanisms that warrant further research to explain these observed patterns.