Gut bacterial composition of two Curculio species and their adaptation to high-tannin food

Abstract:

[Objective] Curculio beetles are major parasitic insects of oak acorns, but the mechanism of their adaptation to high-tannin food (e.g., acorns) is not clear. In this study, we compared the structure and diversity of gut bacteria of the larvae of Curculio arakawai and C. dentipes infested in Mongolian oak (Quercus mongolica) and Liaodong oak (Q. liaotungensis), to elucidate the adaptive mechanisms of weevil larvae to high-tannin food. [Methods] We collected gut samples of weevil larvae for DNA extraction. V3-V4 areas were sequenced using the Illumina MiSeq technology 16S rRNA sequencing. We carried out sequence statistics of Operational Taxonomic Units (OTUs), analysis of species abundance, a and b diversity. [Results] There were 2054 OTUs and 2308 OTUs of the high quality sequences obtained from the guts of the 2 weevil species, in which 481 OTUs were shared. In the gut bacterial community of C. arakawai and C. dentipes, 27 phyla, 145 families and 274 genera were identified as the major taxonomic groups. At the phylum level, Proteobacteria, Bacteroidetes and Firmicutes were dominant in the guts of C. arakawai and C. dentipes. At the genus level, Pseudomonas (63.8%), Serratia (6%) and Acinetobacter (5.2%) were the main groups in the gut of C. arakawai, while Serratia (32%), Rahnella (24.2%), Aeromonas (6.8%) and Rickettsia (6.6%) were dormant in the gut of C. dentipes. Our a diversity analyses showed no significant differences between the gut bacteria of C. arakawai and C. dentipes; however, b diversity showed significant difference between the gut bacteria of C. arakawai and C. dentipes. [Conclusion] Differences in gut bacterial community may be related to differences in species of weevils and host tannin content. We also found several bacteria related to the degradation of tannins, e.g., Serratia marcescens and Lactococcus lactis, which may reflect the adaptive basis for two weevil species to use high tannin food.