A glimpse towards cultivable hemolymph microbiota of marine crabs: Untapped resource for aquatic probiotics/antibacterial agents

Bacterial diseases have turned out to be the primary constraint in sustainable aquaculture production, where, probiotics can play an important role to prevent or control fish and shellfish diseases. As the autochthonous preparations would be more effective than commercial products, continued search for novel antibacterial strains native to aquatic environment are warranted against aquatic pathogens. Further, knowledge on abundance, composition and role of hemolymph microbes is also essential to predict the health status and disease diagnosis. Hence, in present study, 4 commercially significant marine crabs that are important for aquaculture were used to unravel the implication and significance of cultivable hemolymph microbes. Bacterial abundance was found to be individual- and species-dependent; and statistically significant interaction was present between growth media and abundance. Gram negative isolates represented 84% of hemolymph microbes. Vibrio was the principal genera in all species; each carrying a specific hemolymph microbiota (both in terms of abundance and diversity). The present study forms the first report of genera viz., Enterovibrio, Pantoea, Kluyvera and Enterobacter in crustacean hemolymph. Interestingly, new Vibrio species were also found. Further, the study forms the first observation on inhibitory activity of marine crab hemolymph microbes against aquatic pathogens. Overall, the results highlight marine crab hemolymph microbiota as a promising moreover, an untapped resource for probiotics/antimicrobial agents to combat aquatic pathogens. Concurrently, the present study fetches a platform for the prediction of health and disease diagnosis of 4 potentially important aquaculture crab species.