North American fireflies host low bacterial diversity

Although there are numerous studies of fireflies9 mating flashes, lantern bioluminescence, and anti-predation lucibufagin metabolites, almost nothing is known about their microbiome. We therefore used 16S rRNA community amplicon sequencing to characterize the gut and body microbiomes of four North American firefly species: Ellychnia corrusca, Photuris sp., Pyractomena borealis, and Pyropyga sp. These firefly microbiomes all have very low species diversity, often dominated by a single species, and each firefly species has a characteristic microbiome. Although the microbiomes of male and female fireflies did not differ, Photuris sp. gut and body microbiomes did, with their gut microbiomes being enriched in Pseudomonas and Acinetobacter. E. corrusca egg and adult microbiomes differed except for a single egg microbiome that shared a community type with E. corrusca adults, which could suggest microbial transmission from mother to offspring. Mollicutes that had been previously isolated from fireflies were common in our firefly microbiomes. These results set the stage for further research concerning focus on the function and transmission of these bacterial symbionts.