The Effect of Glyphosate And Ciprofloxacin Eexposure On The Gut Bacterial Microbiota Diversity of Rhinella Arenarum (Anura: Bufonidae) Tadpoles

Abstract

The high load of agrochemicals and antibiotics coexisting in aquatic environments within agroecosystems represents a risk for wildlife. As the gut microbiota plays a key role on its host’s functioning and is sensitive to a wide variety of pollutants, its study allows evaluating organisms’ health and therefore, the ecosystem. We studied toxic effects of commercial formulations of a glyphosate-based herbicide (GBH) and the antibiotic ciprofloxacin (CIP) on gut bacterial microbiota diversity of the common toad (Rhinella arenarum) tadpoles, considered a sentinel species. The study was carried out by classic microbiological analysis and matrix-assisted laser desorption ionization-time of flight mass spectrometry. The microbiota from GBH treatment had greater taxa diversity and richness, including some genera, such as Proteus spp. and Yersinia spp. that were absent in control. In contrast, microbiota from CIP treatment registered a decrease of diversity indexes, dominance of Aeromonas spp. and presence of Leclercia spp. The GBH-CIP treatment showed changes in taxa composition, including decrease of Klebsiella spp. and Pseudomonas spp. and trends of individual pollutant treatments. For all cases, changes in the composition of bacterial community (dysbiosis) were linked to a significant decrease in tadpoles’ weight. To the best of our knowledge, this is the first report on the disruption of gut bacterial microbiota of tadpoles by a mixture of two contaminants of emerging concern worldwide. These findings contribute to understanding how the presence of two co-occurring pollutants in freshwaters results in deleterious effects on the amphibian community and potentially affect the microbiota of those environments.