Salinity gradients drove the gut and stomach microbial assemblages of mud crabs (Scylla paramamosain) in marine environments

[Display omitted] •The study investigated the assembly of microbiota in crustaceans.•The potential impacts of different salinity environments in the assembly process of crustacean’s microbiome were determined.•The study revealed that salinity gradients predominantly influenced the microbial communities in the stomach and gut of mud crabs.•The effects of high and low salinities on the structure of gut microbial communities were more pronounced.•Overall functional profiling of gut microbiome was affected by different salinity levels (high verses low salinity). Salinity changes have profound effects on the development, physiology, and molecular activity, as well as the associated microbiome of organisms living in marine and estuarine ecosystems. The associated microbiomes of aquatic organisms are reported to support key physiological functions such as nutrition, reproduction, behavior, and health. The mud crabs, a euryhaline crustacean species, has extra-ordinary ability to survive in a wide range of salinities. Although mud crabs are exposed to diverse salinity conditions, little is known about how these variations affect the symbiotic bacteria they harbor in each environment. This study aimed to deciphering the associated microbiome assembly of mud crabs as well elucidating the potential implications of different salinity conditions in this process. Here, we used high-throughput sequencing to examine how the assemblages of bacteria in the gut of mud crabs are shaped by different salinity gradients. A total of 57 bacterial phyla were detected with Firmicutes and Proteobacteria dominant. A greater difference of microbiome in the gut than stomach of mud crabs indicating guts were more sensitive to different salinity environments. Specific bacterial taxa were enriched in the guts of mud crabs sampled from different salinity settings. Furthermore, functional enrichment analyses also showed that only gut bacteria had significant differences of functions in different salinity levels (high salinity versus low salinity), playing critical roles of signal transduction, and cell growth and death pathways. These results suggested that the microbiota in guts of crabs are more prone to variations in the salinity. These findings provide a comprehensive understanding of the composition and plasticity of mud crabs microbiota, which could lead to innovative strategies development for boosting the aquaculture industry of mud crabs.