Microbial Diversity Affects the Cold Tolerance of Red Swamp Crayfish (Procambarus clarkii) by Regulating Histamine Metabolism.

The red swamp crayfish (Procambarus clarkii) is one of the important freshwater aquaculture species in China, but its growth and development are greatly affected by temperature, which makes it difficult to expand its aquaculture range to the northern regions of China. The composition of gut microbes plays a vital role in resisting environmental pressure, and is also an important driving factor for amino acid metabolism in the body. However, little is known about the relationship between microorganisms, metabolism, and cold-resistance ability of P. clarkii. In this study, we performed the cold-resistance and antioxidant ability test, gut microbiota diversity analysis, quantitative analysis of histamine, and bioinformatics analysis of histamine receptor (HR) family on P. clarkii. The results showed that the cold-resistance crayfish exhibited high antioxidant ability and low gut microbiota diversity after acute cold stress. Next, we also found that there was significant correlation between the Lactobacilli genus and histamine abundance, indicating that the excellent cold tolerance ability of crayfish may stem from the degradation of histamine by Lactobacilli. Finally, it was revealed that HR genes had considerable quantity of gene copies, conservative evolution in crustacean lineages and expression differences in low-temperature tolerant populations. These results suggested that the diversity of Lactobacillus mediated changes in histamine metabolism affect antioxidant capacity, which is one of the reasons why P. clarkii exhibits cold resistance ability. This finding provided a theoretical basis for understanding the microorganism-histamine regulation mechanism of red swamp crayfish under cold stress, promoting the breeding and healthy culture of cold-resistance strain.