Gut microflora of abalone Haliotis discus hannai in culture changes coincident with a change in diet

Development of gut microflora in abalone Haliotis discus hannai cultured at two abalone farms in Japan was similar: (i) gut microflora of juvenile abalones fed on microalgae matched microflora cultured from seawater; and (ii) gut microflora changed coincident with the abalone switching food sources from microalgae to algal pellets. After abalone reached 4 months of age, the gut microflora was replaced by algal polysaccharide-degrading bacteria, which were almost entirely characterized as facultative anaerobes. Dominant species were alginolytic, non-motile fermenters (NMF) and Vibrio spp. The gut microflora seemed to be stable in abalone older than 1 year, with NMF bacteria dominating. Ninety-six percent of the NMF isolates were identified as Vibrio halioticoli by species-specific identification using the colony hybridization method. These results show that abalone H. discus hannai has a unique developmental process in which gut microflora shifts to alginate-degrading bacteria, especially V. halioticoli.