How do male South American lungfish help oxygenate the water around their eggs?

During the spawning season, the male South American lungfish guards the brood within a nest constructed as a vertical passage in the bottom of a watercourse. To help oxygenate the water around the developing young, the male's pelvic fins develop numerous tuft-shaped growths that are filled with small blood vessels (capillaries). It is believed that these specialized growths release oxygen from the blood into the surrounding water.1