Non-mutualistic behavioural traits of tropical cleaner fish revealed through eDNA metabarcoding
Pauline Narvaez1,3, Dr Cecilia Villacorta-Rath2,3
1ARC CoE Centre of Excellence for Coral Reef Studies, James Cook University, Townsville , Australia, 2James Cook University, Townsville , Australia, 3TropWATER, Townsville , Australia
Abstract:
Marine cleaner fish provide a beneficial service and maintain a healthy ecosystem by removing ectoparasites from other ‘client’ fishes. While cleaners are presumed to eat mainly crustacean ectoparasites, morphological identification is challenging due to gut contents becoming rapidly unrecognisable. DNA metabarcoding can help overcoming this challenge by maximising species-level identification. Here, we investigated the diet of the most common tropical cleaner wrasse, Labroides dimidiatus using DNA metabarcoding. Labroides dimidiatus (n=30) were collected at Lizard Island (Great Barrier Reef), guts were immediately removed and preserved. DNA extractions were conducted using the CTAB extraction protocol, and a universal primer targeting the COI gene region was chosen. Libraries were prepared and sequenced at the Australian Genome Research Facility using MiSeq reagent kit v2 (500-cycle). Sequencing data was filtered for genus or species-level taxonomic assignment (97% sequence similarity) and phylum (≥80%), yielding 244 high-resolution OTUs. From these, 191 OTUs (78.3%) were assigned to 36 species of fish and 53 OTUs (21.7%) to three phylum (Chordata, Arthropoda and Mollusca). Taking into consideration current knowledge on cleaner fish ecology and diet, the presence of a high percentage of fish sequences encountered here supports the hypothesis that L. dimidiatus removes fish mucus while cleaning. Fish mucus has higher nutritional value than parasites and therefore, cleaner fish often pick fish mucus over parasites. However, to maintain a mutualistic relationship, parasite consumption is essential, but they were not found in our analysis. Our study provides strong evidence that, in the wild, cleaner fish perform uncooperative behaviour via mucus consumption.
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