# Investigating the lignocellulolytic gut microbiome of huhu grubs (Prionoplus reticularis) using defined diets and dietary switch

## TL;DR

This study explores how diet affects the gut microbiome of huhu beetle larvae, revealing differences in fungal communities based on the type of wood they eat.

## Contribution

The study identifies distinct fungal community responses to different diets in huhu grubs, highlighting their adaptability to lignocellulose substrates.

## Key findings

- Cellulose-reared grubs had abundant potential cellulose degraders in their fungal community.
- Switching from cellulose to lignocellulose diets altered fungal community composition, indicating adaptability.
- Bacterial communities in the gut showed limited dietary influence compared to fungal communities.

## Abstract

The huhu beetle (Prionoplus reticularis) is the largest endemic beetle found throughout Aotearoa New Zealand, and is characterised by feeding on wood during its larval stage. It has been hypothesised that its gut microbiome plays a fundamental role in the degradation of wood. To explore this idea we examined the fungal and bacterial community composition of huhu grubs’ frass, using amplicon sequencing. Grubs were reared on an exclusive diet of either a predominantly cellulose source (cotton) or lignocellulose source (pine) for 4 months; subsequently a diet switch was performed and the grubs were grown for another 4 months. The fungal community of cellulose-reared huhu grubs was abundant in potential cellulose degraders, contrasting with the community of lignocellulose-reared grubs, which showed abundant potential soft rot fungi, yeasts, and hemicellulose and cellulose degraders. Cellulose-reared grubs showed a less diverse fungal community, however, diet switch from cellulose to lignocellulose resulted in a change in community composition that showed grubs were still capable of utilising this substrate. Conversely, diet seemed to have a limited influence on huhu grub gut bacterial communities.