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How does an African lungfish survive a drought while buried in mud?
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Dormancy
Virginia big-eared bats (Corynorhinus townsendii virginianushibernating) are true hibernators, entering a state close to death for much of the winter.
To survive a drought, the African lungfish enters a state of dormancy known as estivation. As water levels recede, the fish burrows into the mud and encases itself in a protective mucous sheath or cocoon that gradually hardens.12
During this period of inactivity, the lungfish undergoes several physiological changes to remain viable for months or even years:
- Respiration: The fish’s gills become nonfunctional, and it relies on a lunglike air bladder for respiration. The cocoon typically features a small tunnel that opens to the surface to allow for air exchange.23
- Metabolism: The fish’s metabolic rate, heart rate, and oxygen requirements fall to very low levels, a state induced by a proteinlike substance that inhibits normal metabolism.13
- Energy and Excretion: The lungfish relies on stored fat reserves for energy. To conserve water, it shifts its excretory process to produce urea instead of ammonia; because urea is less toxic and requires little water for excretion, it allows the fish to survive without access to external water sources.21