What the Labyrinth Organ Actually Is
The labyrinth organ sits just behind the betta's gills, tucked into a chamber lined with folded, highly vascularised tissue, a structure that works like a primitive lung. When a betta rises to the surface and gulps, oxygen passes directly into the bloodstream through that tissue, bypassing the dissolved-oxygen route that other fish depend on entirely. This is why bettas are classified as anabantoids, a group that includes gouramis and climbing perch, all of which evolved this adaptation in the shallow, oxygen-depleted rice paddies, floodplains, and slow streams of Southeast Asia.
