# Comparative Transcriptomics and Intestinal Microbiome Analysis Provide Insights into the Semi-Terrestrial Adaptation of Helice tientsinensis

## TL;DR

This study explores how the crab Helice tientsinensis adapts to land by analyzing its genes and gut microbes.

## Contribution

The study identifies specific gene expression patterns and microbial shifts linked to terrestrial adaptation in Helice tientsinensis.

## Key findings

- Genes related to cytoskeleton, osmotic regulation, and energy metabolism show habitat-specific expression patterns.
- Aquatic habitats show higher abundance of Pseudomonas and Malaciobacter, while Dietzia is more common in semi-terrestrial habitats.
- Upregulated genes like ATP2A and SLC6A3 suggest roles in osmotic regulation during adaptation.

## Abstract

Helice tientsinensis is an excellent model for studying terrestrial crab adaptation. Transcriptome was used to explore the molecular mechanisms of terrestrial adaptation in H. tientsinensis. The genes related to cytoskeleton protein and motor regulation, water and osmotic pressure regulation, and energy metabolism were changed. The differences in intestinal microbiota among habitats further reflect its terrestrial adaptation. These mechanisms provide crucial insights into the adaptability of this important commercial crab species on land.

Helice tientsinensis, a Grapsidae family member, can adapt to terrestrial and semi-terrestrial environments. This study used transcriptomic and microbiome analyses to explore its adaptation mechanisms. Transcriptome analysis showed gene changes related to cytoskeleton–motor, water–osmotic pressure, and energy metabolism. For example, DST was upregulated in the aquatic environment compared to the semi-terrestrial one, and SPAST was downregulated in some groups. ATP2A and SLC6A3 were upregulated with osmotic regulation, and IDH3 was upregulated when comparing the aquatic and semi-terrestrial habitats; at the same time, many energy-related genes were downregulated between the terrestrial and semi-terrestrial habitats. Regarding the gut microbiota, no significant differences in alpha diversity were found between habitats, but there were differences at the genus level. Pseudomonas and Malaciobacter were more abundant in the aquatic habitat, and Dietzia in the semi-terrestrial one. These results provide insights into H. tientsinensis’ terrestrial adaptation, benefiting crustacean evolution study and aquaculture.