Lungfish

Most fish use gills to obtain oxygen from water, but lungfish actually have lungs that allow them to breathe air. They can survive during periods when their watery homes dry up.

Young African and South American lungfish have external gills, just like young tadpoles. This means that they were once thought to be amphibians rather than fish. Lungfish are the only surviving descendants of a very ancient family of fish whose fossilized remains date back over 400 million years. At that time, there were at least 100 different types. Today there are just six. Fossils have shown that the Australian lungfish has remained unchanged in appearance for over 100 million years.The ancestors of this

group lived in the sea, but today lungfish are found only in fresh water.

Survival Experts

When the waters in which they live begin to dry up through lack of rain, lungfish start to breathe air at the water’s surface. Then they build themselves a cocoon in the damp mud, about 10 inches down from the surface. The lungfish produce large quantities of mucus, which helps to seal them into the cocoon. The mucus sets hard, but a breathing tube connects the chamber to the surface, providing oxygen. Their metabolism also slows down at this time, so they need less oxygen. The lungfish usually remain in their cocoons for up to eight months, until the rains arrive.However, they sometimes stay as long as four years in this state of suspended animation before re-emerging when their habitat fills with water again.