Divergence in Gut Bacterial Community Among Life Stages of the Rainbow Stag Beetle Phalacrognathus muelleri (Coleoptera: Lucanidae).

Miaomiao Wang,Xia Wan,Xingjia Xiang

doi:10.3390/insects11100719

Abstract

Simple SummaryPhalacrognathus muelleri is naturally distributed in Queensland (Australia) and New Guinea, and this species can be successfully bred under artificial conditions. In this study, we compared gut bacterial community structure among different life stages. There were dramatic shifts in gut bacterial community structure between larvae and adults, which was probably shaped by their diet. The significant differences between early instar and final instars larvae suggested that certain life stages are associated with a defined gut bacterial community. Our results contribute to a better understanding of the potential role of gut microbiota in a host’s growth and development, and the data will benefit stag beetle conservation in artificial feeding conditions.Although stag beetles are popular saprophytic insects, there are few studies about their gut bacterial community. This study focused on the gut bacterial community structure of the rainbow stag beetle (i.e., Phalacrognathus muelleri) in its larvae (three instars) and adult stages, using high throughput sequencing (Illumina Miseq). Our aim was to compare the gut bacterial community structure among different life stages. The results revealed that bacterial alpha diversity increased from the 1st instar to the 3rd instar larvae. Adults showed the lowest gut bacterial alpha diversity. Bacterial community composition was significantly different between larvae and adults (p = 0.001), and 1st instar larvae (early instar) had significant differences with the 2nd (p = 0.007) and 3rd (p = 0.001) instar larvae (final instar). However, there was little difference in the bacterial community composition between the 2nd and 3rd instar larvae (p = 0.059). Our study demonstrated dramatic shifts in gut bacterial community structure between larvae and adults. Larvae fed on decaying wood and adults fed on beetle jelly, suggesting that diet is a crucial factor shaping the gut bacterial community structure. There were significant differences in bacterial community structure between early instar and final instars larvae, suggesting that certain life stages are associated with a defined gut bacterial community.

Highlights

Insects are the most diverse and abundant class of animals, living in multiple habitats, and feeding on various substrates [1,2]
We investigated the gut bacterial community of P. muelleri across different life stages under artificial breeding conditions through Illumina MiSeq high-throughput sequencing
This is the first study of the gut bacteria of P. muelleri focusing on different life stages

Summary

Introduction

Insects are the most diverse and abundant class of animals, living in multiple habitats, and feeding on various substrates [1,2]. The guts of insects are colonized by diverse microorganisms that play integral roles in their hosts, including affecting the hosts’ metabolism, providing essential amino acids, vitamins and nitrogen for the host, promoting efficient digestion of nutrient-poor diets and recalcitrant foods, aiding the defense and detoxification ability and protecting hosts from potentially harmful microbes [3]. The study of Agrilus mali (Coleoptera: Buprestidae) and Popillia japonica (Coleoptera: Scarabaeidae) has suggested that the metabolic activity of the intestine decreases in the pupal stage and morphology changes during the insects’ metamorphosis influence the associated bacteria communities [3,7]. The guts of beetles are excellent models to study the variety of gut microorganisms that contribute to hosts’ digestion, detoxification, development, pathogen resistance and physiology [1,2,5,9]

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