Linda Kay Nelson, age 12, of Gary, Indiana for her question:

Is it true that the fish in Mammoth Cave are blind?

This vacation season, as usual, half a million sightseers are expected. to visit Mammoth Cave National Park in Kentucky. Many will take a boat ride on an underground river. And a few will glimpse a ghostly pale blindfish seers are expected. to visit Mammoth Cave National Park in Kentucky. Many will take a boat ride on an underground river. And a few will glimpse a ghostly pale blindfish a fish who has never seen even one of his own sightless kinfolk.

Yes, it is true that certain fish in the underground waters of Mammoth Cave are blind.

It is true that the mysterious caves also are inhabited by blind beetles and sightless crickets and crayfish. But the lack of vision is no handicap to these creatures. In fact, eyes would be useless to them. Their natural home is a world of midnight darkness. Here, the creatures with eyes can see no more than those who are blind. Visitors to this underground National Park are taken on guided tours through tunnets revealed by artificial lighting systems. When touring hours are over, the lights are turned off and the fabulous under ground world returns to its natural state of darkness.

A favorite tourist item is a half mile trip on underground Echo River. Beams of light from the walls and the flat bottom boat pierce its inky black waters. Sometimes they reveal a frog or a gaily dotted orange salamander. Sometimes they pick out the shadowy shapes of scurrying fishes and once in awhile, the lights spot a ghostly pink blindfish. The fishy cave dweller is undisturbed by the intruding spotlight because he does not see ix.

He may be almost four inches long. He has fins, but not fishy shales and his pinkish, tinge comes from tiny blood vessels near the surface of his .skin. The darkness of hides normal world does not confuse him because nature has given him special talents to cope with his surroundings. His head, his body and even his tail are covered with sensitive pimples called papillae. These miniature probers are actually tactile organs, somewhat like our special skin cells that sense by touch and feeling.

The blindfish of the midnight caves sense near and distant objects in the surrounding. water. They can swim far and fast and scientists suspect that some of them travel and perhaps migrate through many miles of the caves. After all; Mammoth Cave, Kentucky, is the largest system of caves in the world. Its water carved limestone is riddled, layer upon layer with uncounted miles of tunnels and streams, with many underground lakes and waterfalls.

There are enough unexplored waterways for blindfish to enjoy their midnight world in secret.

Sooner or later, a blindfish senses and meets a mate. Scientists had a hard time solving the secrets of their breeding habits. Some suspected that the mother blindfish gave birth to live babies. But later research proved this to be untrue. Now we know that the cave dwelling female carries her fertilized eggs in special pockets in her gills. There may be 70 eggs in the brood and she has to carry them at least two months before they begin to hatch. The baby blindfish measure less than half an inch.

At least two other types of blindfish live in underground waterways of our limestone cave systems. All of them belong to the fish family Amblyopsidae. This scientific term is coined from older words that tell an expert that these fishes are sightless. They are descended from cave dwelling ancestors who lost the use of their eyes long ages ago. Some specimens have survived in daylight aquariums and after several months their ghostly pink has taken on a dusky tinge with darker bands and blotches.