David Matthews, age 12, of Round Lake, New York, for his question:

What is a lantern fish?

A lantern is expected to shine a light, and when we speak of a lantern jawed face we mean that it has sharp features and a jutting chin somewhat like the profile of an olden style lantern. The name of the lantern fish suggests that he has a lamp or jutting jaw or maybe both these features.

A lantern fish actually does carry his own built in lantern, or more often, a number of lanterns. His lighting system is a biological luminescent process centered in special organs called photophores. Many fishes of the deep ocean have such built in photophores and the midnight depths often sparkle with their darting flashlights of various vivid colors. Most deep sea fishes are built to withstand the tremendous pressure of the water around and above them, and their bodies pop apart when dredged up to lighter surface pressures. The lantern fish is an exception to this general rule.

With swarms of his small cousins, he spends the daylight hours a half a mile or more. down in the heavy midnight ocean along with the toothy hatchet fish and a vast assortment of other illuminated dwellers of the deep. During the day, masses of floating plankton tend to sink down below the heat of the sun. As the water cools after sunset they rise to the surface. The little lantern fishes follow their plankton food supplies. After sunset they rise in teeming swarms to the ocean surface.

In various seas there are 150 species of the lantern fish family. Most of them are like graceful little fingers three to five inches long. The smallest is merely one inch long and the giant of the family measures six inches. The twilight zone casts tricky shadows and the lantern fishes confuse their enemies with two-toned outfits. Their backs tend to be brownish. Their tummies are bright with iridescent shades of silvery gray. And almost every species has a lantern system based on its own design.

The common lantern fish of the Atlantic has neat rows of photophores arranged like buttons along each of his sides. The male also has two or three luminous plates on his back in front of his tail. The female has three to five of these glowing patches on her underside near her tail.

The lantern fishes of the Mediterranean have been studied in detail. Like most fish, they spawn masses of eggs that drift around in the tossing sea. They spawn in late winter. The eggs that hatch become transparent larvae and grow one inch long. They stay in surface waters until they change to their adult bodies. After this metamorphosis, the next generation makes the daily up down migration from deep to surface waters.

When marine biologists began tracing deep sea objects with echo sounding instruments, they found an odd happening. Their echoes were scattered by blankets of objects moving upward after sunset and downward at dawn. They now know that this so called scattering layer comes from echoes bounced from the tiny air bladders belonging to zillions of commuting lantern fishes. This bit of news helped to uncover a whole series of mysterious day night activities among ocean communities of plants and animals.