Izael da Cunha Pantoja sits watching and waiting alongside Dr. Leandro Castello on a rickety wooden bench on the shore of the Amazon River in the State of Pará, Brazil. Suddenly Izael points to undulating water and the rise of a pirarucu, one of the world’s largest freshwater fish. The fish must surface every 15 minutes or so to gulp oxygen through an organ called a cellular swimming bladder. Gulp.
