### Computational methods

Signal sequences and O-glycosylation sites were predicted by SignalIP 3.0 [59] and NetOGlyc 3.1 [60], respectively. Transmembrane regions were determined by SOSUI [61]. For phylogenetic analysis, the zebrafish and pufferfish chemokine protein sequences, together with those of human, were aligned with MAFFT [62] and corrected by a visual inspection. For this alignment, sequences corresponding to the chemokine domain (Pfam PF00048 [63]) were extracted. Amino acid distance matrices, JTT (Jones-Taylor-Thornton) or Dayhoff's (PAM), were then used to infer phylogenetic trees by the neighbor-joining method implemented in the MEGA program package version 3 [64]. Statistical support for the clustering was inferred using the interior-branch test [65]. As the number of sequences in the tree increases, the bootstrap test usually underestimates the extent of statistical support of clusters [65]. The interior-branch test is therefore more preferable for the present analysis than the bootstrap test. Human and other sequences used for the tree construction were taken from the NCBI reference and GenBank files, respectively: XCL1, NP_002986; XCL2, NP_003166; CCL1, NP_002972; CCL2, NP_002973; CCL3, NP_002974; CCL3L1, NP_066286; CCL3L3, NP_001001437; CCL4, NP_002975; CCL4L1, NP_001001435; CCL4L2, NP_996890; CCL5, NP_002976; CCL7, NP_006264; CCL8, NP_005614; CCL11, NP_002977; CCL13, NP_005399; CCL14, NP_004157; CCL15, NP_004158; CCL16, NP_004581; CCL17, NP_002978; CCL18, NP_002979; CCL19, NP_006265; CCL20, NP_004582; CCL21, NP_002980; CCL22, NP_002981; CCL23, NP_665905; CCL24, NP_002982; CCL25, NP_005615; CCL26, NP_006063; CCL27, NP_006655; CCL28, NP_683513; CXCL1, NP_001502; CXCL2, NP_002080; CXCL3, NP_002081; CXCL4, NP_002610; CXCL4LV1, NP_002611; CXCL5, NP_002985; CXCL6, NP_002984; CXCL7, NP_002695; CXCL8, NP_000575; CXCL9, NP_002407; CXCL10, NP_001556; CXCL11, NP_005400; CXCL12, NP_000600; CXCL13, NP_006410; CXCL14, NP_004878; CXCL16, NP_071342; CXCL17, NP_940879; CX3CL1, NP_002987. Channel catfish sequences: SCYA3, AF538720; SCYA101, DQ173276; SCYA102, DQ173277; SCYA103, DQ173278; SCYA104, DQ173279; SCYA104v2, AY555513; SCYA105, AY555502; SCYA106, DQ173280; SCYA107, DQ173281; SCYA108, DQ173282; SCYA109, DQ173283; SCYA110, DQ173284; SCYA111, DQ173285; SCYA112, DQ173286; SCYA113, DQ173287; SCYA114, DQ173288; SCYA114B, DQ182570; SCYA115, DQ173289; SCYA116, DQ173290; SCYA117, DQ173291; pSCYA118, DQ173292; SCYA119, DQ173293; SCYA120, DQ173294; SCYA120B, DQ182569; SCYA121, DQ173295; SCYA122, DQ173296; SCYA124, DQ173297; SCYA126, DQ173298; CCL-A, CB939345; CCL-B, CB940829; CCL-C, CB938694; CCL-D, CB938412; CCL-E, CB937843; CCL-F, CB936843; CCL-G, CB937370; CCL-H, CB938775; CCL-I, BM028237; CCL-J, CB937549; CCL-K, CB936954; CCL-L, CV992304; CCL-M, CV992304; IL8, AY145142; CXCL2-like, AY836754; CXCL10-1, AY335949; CXCL10-2, AY335950; CXCL12, AY836755; CXCL14, AY836756; CXCL-A, BE470298; CXCL-B, CK422021; CXCL-C, BE470282; CXCL-D, CF262322; CXCL-E, CV990129. Rainbow trout: CK1, AF093814; CK2, AF418561; CK2.1, AY372431; CK3, AJ315149; CK4A, CA371157; CK5A, BX910748; CK5B, AY561709; CK6, CA355812; CK7A, Omy.33105; CK7B, Omy.9682; CK8A, Omy.16818; CK8B, CA353159; CK9, Omy.16956; CK10, Omy.34323; CK11, Omy.24120; CK12A, CA358073; CK12B, Omy.15592; CCL-A, Omy.12504; CCL-B, Omy.15908; CCL-C, BX909467; IL8, AJ279069; Vig-7, AF483527; CXCd1, DQ191446; CXCd2, DQ191449; CXCL-A, Omy.24155; CXCL-B, BX859166; CXCL-C, Omy.2417; CXCL-D, Omy.23316; CXCL-E, CX035482; CXCL-F, BX308389. Common carp: CK-1, AB010469; CXCa, AJ421443; CXCb, AB082985; CXCL12a, AJ627274; CXCL12b, AJ536027; CXCL14, AJ536028; IL8, DQ453125. European river lamprey: LFCA-1, AJ231072. Shark SCYA107, AB174767.