1. INTRODUCTION

There are over twenty thousand species of beetles worldwide, distributed across all continents except Antarctica. Notably, beetles play a crucial role in ecosystems. They have the ability to disrupt the breeding habitats of pests and parasites harmful to livestock(deCastro-Arrazola et al., 2023; Gregory et al., 2015), thereby facilitating the spread of human pathogens(Nichols & Gómez, 2014), Additionally, they accelerate the return of nutrients from feces to soil(Sitters et al., 2014), contributing to improved soil aeration, water retention, and fertility(Kirsch, 2011). Moreover, beetles promote plant growth(deCastro-Arrazola et al., 2020), assist in seed dispersal(Pedersen & Blüthgen, 2022), and even provide essential pollination services(Pokhrel et al., 2021; Sakai & Inoue, 1999).
The microbial community within the digestive tract of insects, also known as gut microbiota, comprises protozoa, fungi, archaea, and bacteria(Rozadilla et al., 2020). This diverse consortium plays a crucial role in providing essential nutrients to the host, aiding in efficient food digestion, enhancing host defense mechanisms, and enabling detoxification processes(Kaltenpoth, 2020). Moreover, it exerts a significant influence on various aspects of the host insect’s life, including its lifespan, developmental cycle, mating behaviors, and reproductive capacities(Dong et al., 2021). Despite its importance, research into the gut microbiota of beetles is currently in its early exploratory stages. However, several studies have already unveiled noteworthy findings. For instance, Franzini et al. conducted a comparison of the gut microbiota among two distinct small desert beetle species, revealing intriguing intra-species variations(Franzini et al., 2016). In a separate investigation by Suarez-Moo et al., greater similarity in gut microbiota was observed between the larvae ofCopris incertus Say and the female adults, suggesting a potential mode of vertical transmission that shapes the composition and diversity of offspring gut microbiota(Suárez-Moo et al., 2020). Furthermore, a novel yeast species named Trichosporon heliocopridis , extracted from the gut of Heliocopris bucephalus Fabricius , has exhibited the remarkable ability to assimilate various carbon sources while withstanding environmental stressors such as high temperature, salt, sugar, and ethanol concentrations(Nwaefuna et al., 2021). Additionally, the gut of Thorectes lusitanicus harbors several species belonging to the Actinobacteria phylum, known to produce an array of secondary metabolites with antibiotic properties, thus contributing to host protection(Kaltenpoth, 2009). It’s worth noting that symbiotic bacteria within insects also serve as a significant source for discovering new bioactive small molecules, presenting valuable opportunities for the identification and utilization of beneficial natural products.
Dung beetles, exemplified by Catharsius molossus , are a distinctive group of coprophagous insects that confront specific nutritional challenges within their daily dietary regime. Being reliant on fecal matter as their primary food source, they encounter limitations in accessing adequate nitrogen nutrition, as feces typically harbor low nitrogen content(Madzivhe et al., 2020). Moreover, fecal matter is laden with diverse parasites and pathogens that could potentially impact the health of dung beetles(Woo et al., 2023). In this study, we utilized advanced 16S rRNA high-throughput sequencing technology to extensively scrutinize the diversity and differential composition of the gut microbiota ofCatharsius molossus under conditions of both starvation and refeeding. Our endeavor is centered on unraveling the consequences of periods of food deprivation followed by subsequent refeeding on the structural dynamics of the gut microbiota in Catharsius molossus . This research holds substantial promise in enhancing our comprehension of the intricate ecological functionalities of the gut microbiota in dung beetles, with particular emphasis on the roles assumed by nitrogen-fixing bacteria and the prospective development and application of antimicrobial agents. The outcomes anticipated from this study are poised to contribute significantly to the foundational knowledge of dung beetle ecosystems and the broader domain of physiological ecology, thereby ushering in novel insights and perspectives to this realm of scientific inquiry.