Arapaima Fishing, Amazon River, Brazil

In his book The Whispering Land, naturalist Gerald Durrell reports hearing the tale in Argentina that female arapaima have been seen secreting a white substance from a gland in the head and that their young have been noted seemingly feeding on the substance.
Evolutionary history
Fossils of arapaima or a very similar species have been found in the Miocene Villavieja Formation of Colombia.