[Investigating jellyfish diet with DNA macrobarcoding: A case study in Rhopilema esculentum]

We investigated food composition and feeding selectivity of jellyfish (Rhopilema esculentum) from the coastal aquaculture ponds in Liaodong Bay by DNA metabarcoding technology. The DNA from environmental water samples and stomach contents of R. esculentum were extracted and sequenced by high-throughput sequencing with 18S rDNA V4 region and mitochondrial cytochrome c oxidase subunit I (COI) as metabarcoding markers. Based on 18S rDNA metabarcoding, we detected 27 phyla in the stomach contents of R. esculentum, in which Mollusc was the dominant phylum followed by Arthropod, and 34 phyla in the environmental water samples, in which Pyrrophyta was the dominant phylum followed by Ciliophora and Ascomycota. Using COI metabarcoding, 18 phyla were detected in the stomach contents of R. esculentum, with Mollusc as the dominant phylum and followed by Arthropod. 22 phyla were detected in the environmental water samples, in which Proteobacteria was the dominant phylum followed by Pyrrophyta and Arthropod. Results of both methods indicated R. esculentum food included Mollusc, Arthropod, Streptophyta, Ciliophora, Pyrrophyta, Bacillariophyta, Chlorophyta, fungi, bacteria, etc. We analyzed the feeding selectivity of R. esculentum by the Ivlev selection index and found that they preferred small- and medium-sized zooplankton like Mollusc and Arthropod. Our results showed that DNA metabarcoding technology has the potential to investigate the feeding habits of jellyfish species.