Comparative transcriptomics reveals the immune dynamics during the molting cycle of swimming crab .

Molting is one of the most important biological processes of crustacean species, and a number of molecular mechanisms facilitate this complex procedure. However, the understanding of the immune mechanisms underlying crustacean molting cycle remains very limited. This study performed transcriptome sequencing in hemolymph and hepatopancreas of the swimming crab () during the four molting stages: post-molt (AB), inter-molt (C), pre-molt (D), and ecdysis (E). The results showed that there were 78,572 unigenes that were obtained in the hemolymph and hepatopancreas of . Further analysis showed that 98 DEGs were involved in immunity response of hemolymph and hepatopancreas, and most of the DEGs participated in the process of signal transduction, pattern recognition proteins/receptors, and antioxidative enzymes system. Specifically, the key genes and pathway involved in signal transduction including the , , , three genes in mitogen-activated protein kinase (MAPK) signaling cascade (, , and ), and four genes in Toll pathway (, , , and ). For the pattern recognition proteins/receptors, the lowest expression level of 11 genes was found in the E stage, including , and in the hemolymph, and hepatopancreatic , , , , , and . Moreover, the expression level of , , , , , and in stage C or stage D significantly higher than that of stage E or stage AB. These results fill in the gap of the continuous transcriptional changes that are evident during the molting cycle of crab and further provided valuable information for elucidating the molecular mechanisms of immune regulation during the molting cycle of crab.