# Distinct Gut and Skin Microbiomes of a Carnivorous Caecilian Larva (Ichthyophis bannanicus) Show Ecological and Phylogenetic Divergence from Anuran Tadpoles

## TL;DR

This study explores the gut and skin microbiomes of a carnivorous caecilian larva, revealing distinct bacterial communities and their ecological significance.

## Contribution

The first characterization of gut and skin microbiomes in a carnivorous caecilian larva, highlighting unique and shared bacterial genera.

## Key findings

- Laribacter is enriched in faeces while Flavobacterium dominates on skin.
- Skin microbiome shows higher richness but lower evenness compared to gut microbiome.
- The microbiome of I. bannanicus shares some core bacteria with anuran tadpoles but has unique features.

## Abstract

The amphibian microbiome plays a vital role in host health, yet the bacterial communities of caecilians (Order: Gymnophiona) remain largely uncharacterised. We investigated this by providing the first characterisation of the gut and skin microbiome of larval Ichthyophis bannanicus, a carnivorous caecilian, using 16S rRNA gene metabarcoding. Our analyses show distinct communities between the faecal samples and skin, with significant enrichment of Laribacter in faeces and Flavobacterium on skin. Despite significant variation in their community structures, the core genera Escherichia-Shigella were shared between both regions, suggesting similar microbial exchange in the aquatic environments. Skin bacterial diversity exhibited relatively higher richness, but lower evenness than that of faeces. Further, the skin bacterial community exhibited more complex interactions, suggesting stronger resilience to changes. The relationships and interactions of skin and faecal bacterial communities suggest their interactive effects on the host’s overall health. Compared with anuran tadpoles, the I. bannanicus larval microbiome showed taxonomic overlap, but possessed certain unique core bacteria. This work on an understudied amphibian lineage is foundational, highlighting how diet, phylogeny, and aquatic environment shape microbial communities and informing future research into amphibian health and disease.