There is an unusual type of fish with gills and lungs. Lungfish of several different species are found living in fresh water in Africa, South America, and Australia.
When the water of the lake or stream dries up, the spotted African lungfish will dig a cocoon in the mud and line it with mucus which dries to a hard shell. Its metabolism drops very low, and it uses its lungs to take in oxygen from the air. When the water comes back, the fish fills its lungs with water and swims away.
When the Australian Queensland lungfish (shown in the picture) is getting oxygen through its gills, its pulmonary arteries close and its circulatory system works like that of other fish. When it breathes air, the pulmonary arteries open and the circulatory system is similar to that of other air-breathing animals.
These fish are certainly unique. At first, scientists identified them as reptiles, and then as amphibians, and finally as fish. Scientists assumed that the lungfish was a transitional form between fish and land animals. However, the lungfish fails virtually every test of being a transitional form. In spite of that fact, many textbooks still present these creatures as a “link.” The lungfish is its own animal with its own set of unique characteristics.
We are amazed at the variety of creatures the Creator has given the ability to adapt and live in all areas and climates of the Earth.
© Roland Earnst
Photo Credit: © bigstockhoto.com/DennisJacobsen