Digestive tract contents of bivalves
To determine the food composition of the digestive tract of the bivalves, we carried out metagenome barcoding analysis against the COI gene. Total genomic DNA was extracted from the freeze-dried digestive tract contents of bivalves by using a Lab-Aid824s DNA Extraction kit. Fragments of the gene encoding COI (approximately 300 bp) were amplified by PCR using universal COI primers, with a blocking primer to prevent amplification from the host bivalve species. PCR amplicons from each sample were subjected to high-throughput sequencing by using a MiSeq Genome Sequencer (Illumina) with Miseq Reagent Kit v3 (Illumina).