undergoes several molts in its lifetime. We cloned the chitinase gene from using reverse transcriptase polymerase chain reaction and rapid-amplification of cDNA ends. Primers were designed based on the conserved sequence of chitinase from was 2042 bp, including a 1470 bp ORF (encoded 490 amino acid residues), a 35 bp 5′-UTR, and a 537 bp 3′-UTR. The calculated molecular weight and isoelectric point were 53.44 kD and 4.41, respectively. A homology analysis using BLASTn and BLASTx revealed that the S. serrata. The phylogenetic tree of the chitinase gene generated by the Neighbor Joining method suggested that . The expression of was analyzed by real-time fluorescent quantitative PCR. -mRNA was expressed in all tissues examined and levels were highest in the hepatopancreas, with only low levels of expression in the muscle, stomach, gill, and cuticle, and trace levels of expression in the heart, intestine, thoracic ganglion, and brain ganglion. -mRNA expression in the hepatopancreas peaked during the D stage, and there was a significant difference (<0.05) in expression in the hepatopancreas between stages E, AB, and C. In the cuticle, the level of -mRNA expression increased gradually during the molting cycle, and was significantly higher during D stage than during all other stages (<0.05). Expression levels were relatively low in the stomach throughout the molt cycle. In muscle, -mRNA expression was highest during C stage, but there was no difference in the level of expression between the different molting stages ( is a form of acid chitinase and is expressed abundantly in the hepatopancreas. may play a role in the digestion of chitinous food and the degradation of endogenous chitin during the molting cycle of . Our results lay a foundation for research into the biological function and regulation of chitinase in .