Data from: Gut microbiota of dung beetles correspond to dietary specializations of adults and larvae

Vertebrate dung is central to the dung beetle life cycle, constituting food for adults and a protective and nutritive refuge for their offspring. Adult dung beetles have soft mandibles and feed primarily on nutritionally rich dung particles, while larvae have sclerotized mandibles and consume coarser dung particles with a higher C/N ratio. Here, using the dung beetles Euoniticellus intermedius and E. triangulatus, we show that these morphological adaptations in mandibular structure are also correlated with differences in basic gut structure and gut bacterial communities between dung beetle life stages. Metagenome functional predictions based on 16S rDNA characterization further indicated that larval gut communities are enriched in genes involved in cellulose degradation and nitrogen fixation compared to adult guts. Larval gut communities are more similar to female gut communities than they are to those of males, and bacteria present in maternally provisioned brood balls and maternal ‘gifts’ (secretions deposited in the brood ball along with the egg) are also more similar to larval gut communities than to those of males. Maternal secretions and maternally provisioned brood balls, as well as dung, were important factors shaping the larval gut community. Differences between gut microbiota in the adults and larvae are likely to contribute to differences in nutrient assimilation from ingested dung at different life history stages.

脊椎动物粪便（vertebrate dung）是蜣螂生命周期的核心组成部分：它既是成虫的食物来源，同时也为其后代提供兼具保护性与营养性的栖息庇护所。成年蜣螂拥有柔软的上颚（mandibles），主要取食营养丰富的粪便颗粒；而幼虫的上颚则为硬化（sclerotized）结构，会摄食碳氮比（C/N ratio）更高的粗粒粪便。本研究以中间埃蜣螂（Euoniticellus intermedius）和三角埃蜣螂（E. triangulatus）为实验材料，证实了这种上颚结构的形态适应性，同时也与蜣螂不同生命周期阶段的肠道基础结构及肠道细菌群落差异存在相关性。基于16S核糖体DNA（16S rDNA）特征分析的宏基因组（metagenome）功能预测进一步显示，相较于成虫肠道，幼虫肠道菌群中富集了参与纤维素降解与固氮作用的功能基因。幼虫肠道菌群与雌性成虫肠道菌群的相似性，高于其与雄性成虫肠道菌群的相似性；此外，母虫繁育的育幼球内的细菌，以及母源性‘馈赠’（即伴随卵一同沉积于育幼球中的分泌物）中的细菌，同样与幼虫肠道菌群的相似性高于与雄性成虫肠道菌群的相似性。母虫分泌物、母源性育幼球以及粪便，均是塑造幼虫肠道菌群的关键影响因素。成虫与幼虫肠道微生物群（gut microbiota）的差异，可能会导致不同生命周期阶段的蜣螂在摄取粪便后的营养同化效率存在差异。