Mancozeb exposure induces subtle gut microbiota changes and affects midgut integrity in Brazilian stingless bees...

Widespread fungicidal use in agriculture raises concerns regarding its sublethal effects on pollinators, particularly those that play a critical role in tropical agroecosystems, such as stingless bees, whose health is closely associated with gut microbial communities. This study investigated the effects of the fungicide mancozeb on the gut microbiota and midgut epithelial integrity of two Brazilian stingless bee species, Scaptotrigona aff. postica and Tetragonisca angustula. Both species maintained a conserved bacterial core; however, mancozeb exposure was associated with species-specific changes in community structure (beta diversity). Scaptotrigona aff. postica showed higher bacterial diversity and greater variability in community composition than T. angustula, whereas the latter exhibited stable bacterial diversity patterns and distinct fungal community patterns. Fungal communities were mancozeb-sensitive, with Rhodotorula suppression and stress-tolerant yeast enrichment. Although no genus-level differences were statistically significant following multiple-testing correction, beta-diversity analyses indicated overall differences in community structure associated with host species and exposure condition. Further, semiquantitative histopathological analyses revealed midgut epithelial damage. Overall, mancozeb causes biologically relevant sublethal effects in stingless bees by affecting the gut microbial community structure and causing gut epithelial damage.