Microbiome and novel virus of Oryctes rhinoceros (Coleoptera: Scarabaeidae) in Taiwan

The coconut rhinoceros beetle, Oryctes rhinoceros (Coleoptera: Scarabaeidae), is a major pest of palm crops in tropical Asia and the Pacific Islands. Little molecular data exists for this pest, impeding our ability to develop effective countermeasures and deal with the species’ growing resistance to viral biocontrols. We have been performing increasingly robust molecular analyses of the microbiome of this species across Taiwan, including several 16S metabarcoding assays to understand the microbiome of different sections of its digestive tract during different life stages and in different locations and host plants across Taiwan. This was combined with culturing of living microbes from the digestive tract to test them for cellulolytic abilities.
The larval beetle anatomy has a large hindgut paunch suggestive of bacterial fermentation. Results suggest that the bacteria Citrobacter koseri and Bacillus cereus are symbionts of the beetle, as previous research found these species as well, but they are present in the midgut and hindgut alike and are extremely cosmopolitan species. The yeast Candida xylanolytica was also ubiquitous. Metabarcoding revealed a possible Paracoccus symbiont as well. The gut contents are celluolytic, several microbes could grow on cellulose agar, and the transcriptome contained an endogenosu beetle cellulase enzyme. Curiously, the Oryctes rhinoceros nudivirus was absent from the transcriptome, but a novel virus now named the Oryctes rhinoceros Picorna-like virus was discovered present in all beetles sampled across Taiwan. The pathogenicity of this virus in other Oryctes rhinoceros populations needs to be studied.