Schematic representation of the evolution of teleostean hemoglobin gene clusters. Whole genome duplication (WGD) events are indicated by grey diamonds. The two hemoglobin gene clusters resulting from the teleost WGD are represented as (1) and (2) for Cluster 1 and Cluster 2, respectively (see text). Loss of a hemoglobin gene cluster by excision is indicated by a diagonal slash across that cluster. Although the genome sequence is available for the pufferfish, T. rubripes, the fugu genome was not included in this analysis because the published hemoglobin arrangement of two hemoglobin gene clusters, one containing only α hemoglobin genes and one containing both α and β hemoglobin genes  did not agree with the annotation results of the latest fugu genome assembly reported within the Ensembl database.