Diane Danielewicz, age 15, of Gary, Indiana, for her question:

Were lungfish ever land animals?

There is no evidence that the amazing lungfishes descended from land dwelling ancestors    and a lot of evidence that suggests they did not. It is more likely that their ancestors were ordinary lungless fishes. But it is just possible that their descendants may become bonafide land dwellers in the far future. Everything indicates that the story of life progresses from pills to lungs    and never reverses this direction.

Ile are told that earth's first creatures belonged to the sea and naturally they had gills or some other means to extract dissolved oxygen from the water. Much later, some of them advanced to air breathing lungs and emerged to live on the land. Sometime during the past 20 million years or so, the whales and their chubby cousins returned to life in the sea. But nature never permitted them to trade back their lungs for old style pills. This explains why these and other ocean going mammals must surface to breathe air.

The six known species of lungfish appear to be in a sort of between stage. Like true fishes they have gills, in some cases several pairs of very efficient gills for absorbing oxygen. They also have either one or two simple air sacs to serve as lungs. Hence they are comfortable where no ordinary fish could survive. .

They tend to favor stagnant swamps and mud choked streams where dissolved oxygen is in short supply. Some survive where droughts dry up their water supplies for months or even years. When the oxygen in the water is reduced, a lungfish comes to the surface, opens his big mouth and gulps air into his lungs to sustain himself. But he never attempts to take up the life of a true land dweller.

During a long drought, he encases his long snaky body in a cocoon of mud and lines the inside with a film of moist mucus. There in a foodless, waterless state he waits for the next downpour. He loses a lot of weight and a long drought reduces him almost to scales and bones. But he never attempts to break out and cope with a waterless world.

The evidence from other odd animal features suggests that the lungfish ancestors were ordinary fishes that became trapped in drying regions where the water subsided.

Some of their offspring took to gulping air and a few held it long enough to let oxygen dissolve in their moist internal membranes. After a long period of trial and error, some developed air bladders and survived to become the amazing lungfish. ~r ~

The Australian lungfish may be seven feet long. A smaller species enjoys life in the muddy backwaters of the Amazon and four species in muddy swamps of Africa. At this stage of their history, none of them are advanced enough to live as fish out¬of water. But who knows, perhaps their offspring are destined to progress toward life on the dry land.