Fish hemoglobins. P.C. de Souza and G.O. Bonilla-Rodriguez. Braz J Med Biol Res 2007; 40(6): 769-778.  

Figure 1. Hemoglobin molecule with four globin chains, two alpha-like and two beta-like chains each bearing a heme group, responsible for the reversible binding of oxygen. The figure was generated by Pymol 0.99 (DeLano Scientific LLC, Palo Alto, CA, USA) using a pdb file (1OUU) from trout hemoglobin, Oncorhynchus mykiss.