Microbial diversity in the larval gut of field and laboratory populations of the sugarcane weevil Sphenophorus levis (Coleoptera, Curculionidae)

The sugarcane weevil, Sphenophorus levis, is a wide-spread sugarcane pest in Brazil. Sphenophorus levis may depend on microorganisms that inhabit its intestinal tract. We examined the diversity of the gut microbiota of S. levis, which was characterized using culture-dependent and culture-independent methods. Analysis of 16S rRNA amplified directly from the gut community revealed the presence of 14 genera, one group from the Candidatus category, one uncultured group assigned to the family Flavobacteriaceae, and one uncultured group assigned to the family Enterobacteriaceae; all of them are members of the Alpha-Proteobacteria, Beta-Proteobacteria, Gamma-Proteobacteria, Firmicutes, and Bacteroidetes phyla. Microorganisms isolated through culture-dependent methods were classified according to morphological parameters and by 16S rRNA gene sequences. In addition to bacteria, four filamentous fungi were isolated. A higher bacterial diversity was observed in field populations of larvae than in laboratory populations, according to the Shannon index (Field H' = 3.36; Laboratory H' = 3.26). Five genera of bacteria and two filamentous fungi were found to have cellulolytic activity. This is the first report of S. levis gut microbiota; it may contribute to development of strategies for controlling this sugarcane pest.