Lungfish breathe through a combination of gills and lungs, meaning they can breathe both in water and air. They breathe through their mouth as well as respire through their gills. Critically, they must have access to air, or they will drown.
Here's a more detailed breakdown:
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Gills: Like most fish, lungfish possess gills, which allow them to extract oxygen from the water. Water passes over the gills, and oxygen is absorbed into the bloodstream while carbon dioxide is released.
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Lungs: Unique among fish, lungfish have true lungs that function much like the lungs of terrestrial vertebrates. These lungs are connected to their esophagus. When the oxygen level in the water decreases, or the water dries up, lungfish surface and gulp air into their lungs. They essentially "breathe" air, supplementing or replacing gill respiration.
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Obligate Air Breathers (in some cases): Depending on the species and environmental conditions, some lungfish are obligate air breathers. This means that even if the water is well-oxygenated, they must surface to breathe air, or they will drown. This is because their gills are insufficient to provide enough oxygen for their needs.
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Aestivation: During periods of drought, some lungfish species can survive for months, or even years, by entering a state of dormancy called aestivation. They burrow into the mud, secrete a mucus cocoon to prevent water loss, and breathe air using their lungs until the rains return. Their metabolism slows dramatically during this time.
Here's a summary in table format:
| Breathing Method | Description | When Used |
|---|---|---|
| Gills | Extract oxygen from water | When water is available and oxygenated. |
| Lungs | Breathe air taken in at the surface | When water is low in oxygen or during drought conditions. Also, obligatory for some species, at all times. |
| Aestivation | Burrowing into mud and breathing air within a mucus cocoon, while dormant. | During prolonged drought conditions. |
In conclusion, lungfish employ a dual respiratory strategy using both gills and lungs. The relative importance of each method depends on the species of lungfish and the environmental conditions it faces.
