By RACE-PCR,immunoglobulin M heavy chain (H) and immunoglobulin light (L) chain cDNAs have been cloned and characterized from snakehead Channa argus.The IgH cDNA was found to be 1 912 nucleotides (nt) and contains an open reading frame (ORF) of 1 797 nt that is translated into a putative peptide of 598 amino acids (aa).The constant region (CH1-4) of IgH each contain a pair conserved Cys residues which may be responsible for the formation of intra-domain disulfide bridge.The Cys of CH1 may be concerned with inter-chain disulfide bridge,four N-linked glycosylation sites are located in CH1,CH2 and CH4 respectively.The multiple sequence alignment reveal the presence of a remarkable insertion at the CH1-CH2 boundary,result in a CH1，CH2 hinge peptide longer than other teleost IgH,respectively.Noteworthy,the Cys in CH4 is substituted by Lys in snakehead fish,that not find in other teleost IgH.Protein sequence of snakehead IgH has 55%,50％,45％,36％ and 28％ identical to orange-spotted grouper,blackfin icefish,bastard halibut,rainbow trout and zebrafish IgH,respectively.The IgL cDNA was found to be 941 nt and contains an ORF of 729 nt that translates into a putative peptide of 242 aa.The cysteine residues involved in the formation of disulfide bonds are completely conserved among fish IgL.Snakehead IgL exhibits 78%,77%,32% and 31% overall identity to Japanese amberjack,spotted wolfish,channel catfish and rainbow trout IgL,respectively.The phylogenetic tree of fish IgH conserved region contains two major branches of teleost and elasmobranch,and snakehead IgH is most closely related to pufferfish.The phylogenetic tree of IgL conserved region shows three major branches,and snakehead IgL locate as a branch of IgL1A.