The study aimed to better understand the constitution and expression pattern of common carp(Cyprinus carpio)globin family,and their contributions to hypoxia adaptation of the species.Complete gene sequence of common carp neuroglobin(Ngb)was obtained by BLAST searching in draft genome sequence and screening in full-length cDNA library,proving that Ngb gene co-existed in common carp genome with myoglobin-2(Mb-2),a unique paralog of globin previously reported to be specifically expressed in brain.Quantitative real-time PCR results indicated that common carp Ngb gene expression was brain-specific and hypoxia responsive.Ngb expression was up-regulated during the aquatic surface respiration,and followed by a decline when the fish fell into coma,then no significant change in Ngb expression was observed during the reoxygenation recovery.Analysis on gene structure and phylogeny indicated that teleost Ngb genes were highly conserved,suggesting that common carp Ngb might have similar protein structure and biological functions to its zebrafish ortholog,while distinct from the paralogous Mb-2.Expression quantity was significantly different between two common carp strains with distinct hypoxia tolerance.Nearly 10 times higher Ngb expression was detected in the hypoxia tolerant mirror carp.These results suggested that Ngb and Mb-2 might serve the brain in different ways,to accomplish better oxygen delivery and neuron protection against hypoxia,playing an important role in hypoxia adaptation of common carp.