Objective Transcriptomics of the two primary subpopulations of circulating hemocytes representing the distinct stages of immune cell differentiation in crayfish, semi-granular cell (SGC) and granular cell (GC), was studied.

Methods SGC and GC in Cherax quadricarinatus were isolated and purified by means of Percoll discontinuous density gradient centrifugation. Transcriptome sequencing and analyses of differential expression, gene ontology (GO) enrichment, and Kyoto encyclopedia of genes and genomes (KEGG) enrichment on them were conducted. RT-qPCR was employed to validate the expressions of the differentially expressed genes (DEGs).

Results The sequencing identified 116199 unigenes in the C. quadricarinatus hemocytes with an average length of 763 bp and an N50 of 1313 bp. The 4488 DEGs included 3951 significantly upregulated in SGC and 537 in GC. On cellular components, there were 7 GO enrichment bands in SGC and 10 in GC; on molecular functions, 31 in SGC and 60 in GC; and on biological processes, 154 in SGC and 102 in GC. The KEGG analysis found 44 pathways enriched in SGC and 10 in GC.

Conclusion The DEGs enriched in SGC primarily involved in cellular proliferation, differentiation, transcriptional regulation, enzyme synthesis, endocytosis, and adhesion processes. Whereas those enriched in GC were basically associated with the transmembrane transport, metabolic pathways, prophenoloxidase system, phagocytosis, and antimicrobial peptide synthesis.