Insect microbiomes influence many fundamental host traits, including functions of practical significance such as their capacity as vectors to transmit parasites and pathogens. The knowledge on the diversity and development of the gut microbiomes in various blood feeding insects is thus crucial not only for theoretical purposes, but also for the development of better disease control strategies. In Triatominae (Heteroptera: Reduviidae), the blood feeding vectors of Chagas disease in South America and parts of North America, the investigation of the microbiomes is in its infancy. The few studies done on microbiomes of South American Triatominae species indicate a relatively low taxonomic diversity and a high host specificity. We designed a comparative survey to serve several purposes: (I) to obtain a better insight into the overall microbiome diversity in different species, (II) to check the long term stability of the interspecific differences, (III) to describe the ontogenetic changes of the microbiome, and (IV) to determine the potential correlation between microbiome composition and presence of Trypanosoma cruzi, the causative agent of Chagas disease. Using 16S amplicons of two abundant species from the southern US, and four laboratory reared colonies, we showed that the microbiome composition is determined by host species, rather than locality or environment. The OTUs (Operational Taxonomic Units) determination confirms a low microbiome diversity, with 12-17 main OTUs detected in wild populations of T. sanguisuga and T. protracta. Among the dominant bacterial taxa are Acinetobacter and Proteiniphilum but also the symbiotic bacterium Arsenophonus triatominarum, previously believed to only live intracellularly. The possibility of ontogenetic microbiome changes was evaluated in all six developmental stages and feces of the laboratory reared model Rhodnius prolixus. We detected considerable changes along the host's ontogeny, including clear trends in the abundance variation of the three dominant bacteria, namely Enterococcus, Acinetobacter, and Arsenophonus. Finally, we screened the samples for the presence of Trypanosoma cruzi. Comparing the parasite presence with the microbiome composition, we assessed the possible significance of the latter in the epidemiology of the disease. Particularly, we found a trend toward more diverse microbiomes in Trypanosoma cruzi positive T. protracta specimens.

30Insect microbiomes influence many fundamental host traits, including functions of practical 31 significance such as their capacity as vectors to transmit parasites and pathogens. The 32 knowledge on the diversity and development of the gut microbiomes in various blood 33 feeding insects is thus crucial not only for theoretical purposes, but also for the development 34 of better disease control strategies. In Triatominae (Heteroptera: Reduviidae), the blood 35 feeding vectors of Chagas disease in South America and parts of North America, the 36 investigation of the microbiomes is in its infancy. The few studies done on microbiomes of 37 South American Triatominae species indicate a relatively low taxonomic diversity and a high 38 host specificity. We designed a comparative survey to serve several purposes: I) to obtain a 39 better insight into the overall microbiome diversity in different species, II) to check the long 40 term stability of the interspecific differences, III) to describe the ontogenetic changes of the 41 microbiome, and IV) to determine the potential correlation between microbiome 42 composition and presence in the vector gut of Trypanosoma cruzi, the causative agent of 43 Chagas disease. Using 16S amplicons of two abundant species from the southern US, and 44 four laboratory reared colonies, we showed that the microbiome composition is determined 45 by host species, rather than locality or environment. The OTUs (Operational Taxonomic 46 Units) determination confirms a low microbiome diversity, with 12-17 main OTUs detected 47 in wild populations of T. sanguisuga and T. protracta. Among the dominant bacterial taxa are 48 Acinetobacter and Proteiniphilum but also the symbiotic bacterium Arsenophonus 49 triatominarum, previously believed to only live intracellularly. The possibility of ontogenic 50 microbiome changes was evaluated in all six developmental stages and faeces of the 51 laboratory reared model Rhodnius prolixus. We detected considerable changes along the 52 host's ontogeny, including clear trends in the abundance variation of the three dominant 53 bacteria, namely Enterococcus, Acinetobacter and Arsenophonus. Finally, we screened the 54 samples for the presence of T. cruzi. Comparing the parasite presence with the microbiome 55 composition, we assessed the possible significance of the latter in the epidemiology of the 56 disease. Particularly, we found a trend towards more diverse microbiomes in T. cruzi positive 57 T. protracta specimens.