A lungfish sleeps through the drought

When its pool vanishes, an African lungfish burrows, secretes a cocoon of mucus, and estivates. Animals have been watched in that state for many months, and the classical accounts run past a year.

Protopterus has lungs as well as gills, which is why a drying swamp is not immediately fatal. As the water goes, the fish digs, curls, and wraps itself in dried mucus that slows the loss of water. Heart rate and oxygen use fall to a small fraction of the active animal. Waste is handled without urinating. In this state a fish has been kept, and revived, after many months, and the classical accounts run to more than a year.

It is not sleep in the sense of a brain cycling through the night, and it is not the frozen frog already in this library, which is solid ice with a beating heart stopped. The lungfish stays soft, warm as the mud is warm, and barely alive by design. When rain floods the burrow the cocoon softens and the fish is a fish again. The drought is a season the species treats as a room.