Adult african lungfish are obligate airbreathers. While they spend most of their time in shallow water, they must come up at least once an hour for air. When needed, the lungfish will pop its head above water and open its mouth. The hyoid arch of the fishs jaw will retract, opening the oropharyngeal cavity in the mouth. This creates a negative pressure, unlike what occurs with our own lungs, and allows fresh air to fill the cavity. Once full, the glottis opens, allowing passage to the lung. Air already in the lung will be expelled, passing over the fresh new air in the oropharygeal cavity. Unfortunately some old and new air mixes, so this process is not entirely efficient. Elastic recoil occurs as the lung deflates, causing the shape of the lungfish itself to deflate with it. The mouth of the lungfish will then close and its hyoid arch will return to its position, closing the oropharyngeal cavity. The fresh new air in this cavity will instead be directed to the lung, filling it. After this process, the lungfish is free to sit at the bottom of its shallow pool of water, gobbling up shrimp or other small organisms until it needs to breath again.
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