Diversity of Bacteria Associated with Guts and Gonads in Three Spider Species and Potential Transmission Pathways of Microbes within the Same Spider Host

SIMPLE SUMMARY: Despite extensive research into the microbial communities of insects, studies on spiders, an important arthropod group, have been relatively limited in the field of microbiology. This study focuses on the analysis of gut microbiota and gonad microbiota from three different spider species. Using high-throughput sequencing, we have identified variations in microbial composition among different spider species, particularly notable differences between female and male spiders. Sequencing results also suggest similarities between the gut and ovarian microbiota of spiders, implying potential pathways for microbial transmission within female spiders between the gut and gonad. This research provides a theoretical foundation for exploring the relationship between microbes and spider hosts, as well as the role of microbes in spider physiology, ecology, and behavior. ABSTRACT: Microbial symbiosis plays a crucial role in the ecological and evolutionary processes of animals. It is well known that spiders, with their unique and diverse predatory adaptations, assume an indispensable role in maintaining ecological balance and the food chain. However, our current understanding of spider microbiomes remains relatively limited. The gut microbiota and gonad microbiota of spiders can both potentially influence their physiology, ecology, and behavior, including aspects such as digestion, immunity, reproductive health, and reproductive behavior. In the current study, based on high-throughput sequencing of the 16S rRNA V3 and V4 regions, we detected the gut and gonad microbiota communities of three spider species captured from the same habitat, namely, Eriovixia cavaleriei, Larinioides cornutus, and Pardosa pseudoannulata. In these three species, we observed that, at the phylum level classification, the gut and gonad of E. cavaleriei are primarily composed of Proteobacteria, while those of L. cornutus and P. pseudoannulata are primarily composed of Firmicutes. At the genus level of classification, we identified 372 and 360 genera from the gut and gonad bacterial communities. It is noteworthy that the gut and gonad bacterial flora of E. cavaleriei and L. cornutus were dominated by Wolbachia and Spiroplasma. Results show that there were no differences in microbial communities between females and males of the same spider species. Furthermore, there is similarity between the gut and ovary microbial communities of female spiders, implying a potential avenue for microbial transmission between the gut and gonad within female spiders. By comprehensively studying these two microbial communities, we can establish the theoretical foundation for exploring the relationship between gut and gonad microbiota and their host, as well as the mechanisms through which microbes exert their effects.