Synteny maps. Synteny maps comparing the orthologues of the relaxin family loci (RFL) and the genes flanking them in humans (H. sapiens) and five species of teleosts (G. aculeatus, D. rerio, T. nigroviridis, T. rubripes and O. latipes). 1A) RFLA locus contains the INSL5 gene in humans and its teleostean paralogues, insl5a/insl5b; 1B) RFLB locus in humans hosts four relaxin family genes, namely INSL6, INSL4, RLN2 and RLN1; in teleosts this locus is represented by rln gene found as a single copy in all of the analyzed teleost genomes except for D. rerio, in which it is absent; 2A) RFLCI locus is represented by RLN3 in humans, and its paralogues, rln3a/rln3b in teleosts; 2B) RFLCII locus hosts INSL3 in humans, while 3 of the 5 studied teleosts contain single copy orthologues, insl3. The chromosome number (in Roman numerals) and map position of each gene in humans are given on the right. On the left, the genes orthologous to the human RFL are shown by orange hexagons in the central shaded section, and RFL paralogue that arose via the whole genome duplication shown as a white hexagon. Genes flanking the RFL that are syntenic in humans and teleosts are indicated by orange rectangles; the map position of each gene in teleosts is listed in Additional File 1: Table S3. Tandem duplicate copies of genes appear as two rectangles. Genes shown as white rectangles are genes identified on the same chromosome but in more distant locations (Additional File 1: Table S1). The genes PDE4B/SLC35D1/SERBP1/RPE65 (RFLA); JAK2 (RFLB); TNPO2/RFX1/ASF1B/SLC27A1/GLT25D1 (RFLCI); and MED26/NR2F6/UNC13A/KCNN1/MAST3 (RFLCII) were all retained in duplicate in 3 or more species (Additional File 1: Table S1). One gene, NXNL1 RFLCI) was retained tandemly duplicated in 3 species. Three of the 4 RFL linkage groups contained a copy of JAK, and 2 of the 4 contained copies of PDE, SMARCA, RFX and MAST genes.