Betta respiratory system — gills and the labyrinth organ
Overview of betta respiration — gill arches ventilated by opercular pumping alongside a labyrinth organ that takes oxygen directly from air gulped at the water surface.
General educational reference only — not clinical or veterinary advice. Anatomy varies between individual animals; consult a licensed veterinarian for any health concern.
Gills and opercular pumping
The betta has the standard teleost gill apparatus: four pairs of gill arches, each carrying two rows of filaments whose surfaces are folded into thin lamellae where gas exchange occurs. Water is drawn in through the mouth and pushed across the gills by coordinated movement of the mouth floor and the opercula, the bony gill covers. Blood runs through the lamellae counter to the water flow, holding a diffusion gradient along the whole exchange surface.
The labyrinth organ
Bettas belong to the anabantoids, fishes that carry an accessory air-breathing organ. A chamber above the gills, the suprabranchial cavity, houses the labyrinth organ: a rosette of thin bony plates grown from the first gill arch and covered in richly vascularized mucosa. The folded plates pack a large respiratory surface into a small space, and blood passing through the mucosa takes up oxygen directly from swallowed air.
Air breathing at the surface
The fish rises to the surface, takes a bubble of air into the mouth and passes it into the suprabranchial chamber, releasing the spent air through the opercular opening. The labyrinth organ is not present at hatching; it develops over the first weeks of life, and fry rely on their gills until it does. In adults aerial respiration becomes a required part of gas exchange rather than an optional supplement.
