Immobilization antigens. (a) Unrooted neighbor-joining phylogenetic tree  of the 17 Ich immobilization antigen genes. The three described in the text as being related to previously identified genes are in blue. (b) Scaffolds containing arrays or tandem duplications of putative immobilization antigen genes (blue arrows) and pseudogenes (red outlined arrows). Locus accessions identify the individual genes. GenBank accession numbers for scaffolds 1 to 4 are as follows: 1, GL983567; 2, GL983846; 3, GL984331; 4, GL984394.