Ventral View (Skull)
Notes: Bowfin use a countercurrent flow system to extract oxygen from water (water flows over lamellae in opposite direction of blood flow). This process occurs in three steps: 1) operculum closes, mouth opens, branchiostegal rays spread (picture A), and buccal cavity enlarges. 2) operculum cavity enlarges, operculum still closed, and water flows over abducted gill filaments. 3) buccal and operculum cavities reduced, mouth closes, branchiostegal rays close (picture B), and pressure forces water out through the operculum.