Comparative Transcriptomics and Intestinal Microbiome Analysis Provide Insights into the Semi-Terrestrial Adaptation of .

, 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, was upregulated in the aquatic environment compared to the semi-terrestrial one, and was downregulated in some groups. and SLC6A3 were upregulated with osmotic regulation, and 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. and were more abundant in the aquatic habitat, and in the semi-terrestrial one. These results provide insights into ' terrestrial adaptation, benefiting crustacean evolution study and aquaculture.