Supplementary Diets Impact the Abundance of Core Bacteria in the Gut of a Managed Stingless Bee but Not Its Fat Body Size

The management of stingless bees is an expanding activity that requires technical knowledge in order to face a number of challenges, from malnutrition to disease. In the present study, we evaluate the effect of supplementary diets based on sucrose (100% sucrose syrup or 50% sucrose syrup + 50% dried spirulina) on fat body mass and on the gut-associated microbiota of Melipona quadrifasciata, one of the most important species in Brazilian stingless bee farming. The study was performed over 5 months, from the end of spring until the end of summer, when outbreaks of an annual disease occur. Both the fungal and bacterial microbiota were metabarcoded using ITS2 and 16S gene markers, respectively. Our experimental design aimed at incorporating both seasonal and treatment effects of diet on forager gut microbial composition. Our analyses show that supplementing bees' diet with sucrose-based feed does not affect the amount of fat body of forager bees. In contrast, it alters the composition of the gut microbiota characterised by an increase in the relative abundance of acetic acid bacteria and unclassified lactobacilli. The significance of such changes promoted by a sucrose-rich gut environment concerning bee health needs to be further investigated and carefully considered for stingless bee management.