Prokaryotic and eukaryotic microbial community in Kumamoto oyster (Crassostrea sikamea) larvae: Response to antibiotics in trace concentration

Background: Antibiotic is regarded as an emergency measure to avoid disease occurrence of aquatic animals during metamorphosis in an aquaculture system, which is very common in hatcheries of bivalve mollusc larvae. However, it is still unclear how and to what extent the antibiotic addition affect the prokaryotic and eukaryotic microbial communities of marine bivalve larvae. Methods: and results: We profiled the community compositions and dominant taxonomies of prokaryotic and eukaryotic microbiota of Kumamoto oyster ( Crassostrea sikamea ) larvae exposed to seawater with antibiotics in trace concentration. A total of 500,664 16S rRNA and 501,933 18S rRNA gene fragments were selected for classification, resulting in 714 prokaryotic OTUs and 47 eukaryotic OTUs. Antibiotic exposure altered the structure of the larval microbiome, and increased the prokaryotic but decreased the eukaryotic microbial diversity. The larval microbiota were sensitive to antibiotics, as evidenced by the alternations of the dominant bacterial phyla Proteobacteria, Bacteroidetes, Firmicutes, Chlamydiae, and Actinobacteria, and eukaryotic phyla Streptophyta, Cercozoa, Chlorophyta and Haptophyta. Similarly, significant effect was observed at the family and genus level, especially the increased bacterial Devosiaceae, Microbacteriaceae, Halieaceae, Vibrionaceae family, and Devosia , Stappia and Vibrio genus, and eukaryotic Isochrysidaceae and TAGIRI1-linage family and Tisochrysis genus. Conclusions: : These results indicate that antibiotics may induce a shift in the larval microbiome, which may cause an unstable community structure and in turn affect the oyster health.