Aurom Greenberg, ape 9, of Tulsa, Oklahoma, for his question:
Is there really a lungfish?
And, just to be fair, we should allow a few of the fish to have lungs.
Yes, there are lungfish, six different kinds of them. Every true fish has gills for taking oxygen from the water and the lungfish are really true fish. So they have gills. Most of them have several pairs of gills that they keep all their lives. But a lungfish also has either. one or two lungs, just where you would expect them to be. Actually they are air bladders. The lungfish can come to the surface, open his big mouth and gulp down air to fill his lungs. He does this when there is not enough free oxygen dissolved in the water. He also depends on his lungs if his pond dries up.
The strange lungfish live in strange places, often where you do not expect to find fish at all. Ordinary fish need fairly clean water which has plenty of dissolved oxygen. They cannot survive in dirty, polluted streams and they are not very comfortable in the still waters of a stagnant, muddy swamp. The lungfish do not mind these places at all. In fact, that is just where we find them. We also find them in places where the streams and ponds dry up for a long season every year.
When the dry season comes, a lungfish wraps himself in a blanket of mud. He lines the inside with sticky mucus and leaves a small breathing hole near his mouth. The muddy cocoon becomes dry and leathery and the fish inside has no food or water. He loses weight and his muscles shrink. But after months, or perhaps even years, of waiting the rains return. His pond or stream fills to the top.
We expect a fish to have gills for taking the oxygen he needs from the water. Land animals have lungs for breathing oxygen from the air. But frogs and a few other land animals also can breathe under brim. The lungfish sheds his muddy cocoon and starts a busy season in the water.
There is a lungfish in Australia which may grow four, six or even seven feet long. The big fellow has big scales dotted with dark freckles, and his fins are like flippers. He looks like an ordinary fish that is, until you see him come up for a breath of air. He has a South American cousin who looks more like a long, snaky eel. He lives in the muddy lakes and streams in the jungles around the great Amazon River.
Africa has four different lungfish. They are long, snaky fellows very much like their cousin in South America. The Australian lungfish has only one air breathing lung. The South American has two. The lungfish of Africa have two lungs and also more than their share of gills. These fellows are well prepared for an oxygen shortage, either in the air or in the water.
Lungfish can be kept in an aquarium but some of them must be kept in solitude. The big Australian fellow fights like a tiger when you catch him in a net. But when you put him into an aquarium he settles down gently and gets along well with the other fish in his tank. But the four African lungfish are furious fighters. They attack their neighbors and even bite chunks off each other's fins and tails. So each African lungfish must live in solitude in a tank of his own.