The microbiome of Callosobruchus maculatus affects mating and locomotion
The gut and cuticular microbiomes of insects can influence life history traits and behaviors, as demonstrated in several model and non-model insect species. We sought to address the hypothesis that the microbiome of the seed beetle Callosobruchus maculatus influences mating behavior and outcomes. We surface sterilized the beetle eggs and the food source on which they develop, and examined the effect on microbial community structure, beetle life history traits, and behaviors. The microbial community of surface sterilized and control newly emerged adult beetles was characterized using 16S rRNA gene sequencing. Surface sterilization changed the beetle microbiome such that community diversity was reduced and community structure was altered. When comparing the taxonomic structure between surface sterilized and control beetles, both communities were dominated by a genus from the family Rikenellaceae, however relative abundances of Rikenellaceae, Bacillus, Clostridiales, and several Proteobacteria were depleted in surface sterilized beetles as compared to controls. Life history traits were affected by surface sterilization: surface sterilized male and female beetles weighed more, and surface sterilized females had higher fecundity, compared to controls. We found that surface sterilization also affected mating behavior. Surface sterilized beetle pairs had a higher percentage of successful matings and a shorter mating latency period than control beetles. In mate choice tests in which a female was presented with either a surface sterilized or control male, females were more likely to mate with surface sterilized males. Finally, surface sterilized beetles exhibited increased locomotion and hyperactivity, which likely increased chances of successfully mating. We discuss possible bidirectional communication existing between the insect brain and the microbiome, leading to modulation of host neurotransmitters and increased locomotion to influence mating behavior.