Abstract: The members of Ly-6/uPAR superfamily distribute widely in many metazoans. All proteins from this family have at least one conserved Ly-6/uPAR (LU) domain which is composed of about 70 to 100 amino acids, and contain 8 to 10 cysteine residues with a defined disulfide-bonding pattern. The members of Ly-6 family are classified into two subfamilies, namely GPI-anchored membrane proteins and secreted proteins, according to whether they possess the glycophosphatidyl inositol (GPI)-anchored signal sequence in the C-terminus. In this study, we cloned and characterized a new member of Ly-6 superfamily in gibel carp (Carassius auratus gibelio). The full-length sequence of this gene consisted of 570 base pairs that encoded 99 amino acids and had only one LU domain. Our analysis using on-line bioinformatic software showed that this protein might have one signal peptide but no GPI-anchor signal sequence, thus could be a type of secreted protein. We conducted RT-PCR to detect its expression in different tissues and found that this protein was specifically expressed in testis. According to its characteristics, we named the gene Carassius auratus gibelio testis-specific Ly-6/uPAR related protein (CagTslurp). In situ hybridization revealed the expression of CagTslurp in spermatogonia, primary spermatocytes, secondary spermatocytes and spermatids, but not in somatic cells. These results indicated that the CagTslurp gene might play a role in spermatogenesis of gibel carp.