Lanita Hathaway, age 11, of Murray, Utah, for her question:

What is a fairy shrimp?

This dainty creature is not a true shrimp, but it could pass for a miniature water fairy. Our American fairy shrimp is very similar to several cousins in the Old World. Some are at home in fresh water and some in salty water, but wherever they make their home, as a rule we do not notice them. The fairy shrimp is only distantly related to the true shrimps of the salty sea. You might mistake the tiny creature for a junior shrimp  until you remember that a true shrimp is a ten legged decapod animal. The fairy shrimp has 11 pairs of legs, branched like leafy foliage. They are arranged in two rows of fringe along the underside of his body. Since he measures only about one tenth of an inch, you will need a good magnifying lens to examine him and count his leafy legs. He has a bulky ?Pad and a long jointed tail ending in a two pronged fork. He is a crustacean and his small body is covered with crisp, jointed shell material.

It may be difficult to identify and place him in the animal kingdom, but you will see at once why he is called a fairy shrimp and no doubt agree that no better everyday name could have been chosen for him. His small body is almost transparent and it may be tinted delicately with rosy pink, palest lavender or some other pastel color. His transparency makes him almost invisible in the water. But if you can spot him, you will watch with delight his swooping and sweeping, twisting and twirling acrobatics. There are sure to be relatives in the same pond, and together they perform a fairy water ballet that is both graceful and sprightly.

The family life of the fairy shrimp is very odd. Sometimes only one parent is required to produce the fertilized eggs. And the eggs not only survive a period of drought, they need it. The fairy creatures favor life in shallow pools that tend to dry up from time to time. This leaves the eggs stranded, and there they rest for long or short periods of time. They hatch when water again fills their ponds. But as a rule, they do not hatch at all unless they have previously been through a drying out period.

Fairy shrimp are related to a large assortment of water fleas and other miniature crustaceans. In some lakes, there may be 40,000 of these little crusty cousins in a cubic yard of water  though you might never notice them. Many of them are swept along the waterways to larger streams and rivers. There they become food for larger fish. Many of our favorite food fish such as the shad fatten themselves on fairy shrimp salad. Other fairy shrimp live at the margin of the sea and provide food for lazy flounders.

The fairy shrimp are classified as branchiopods, a scientific term meaning branching feet. Actually, it is their legs that are branched like feathery foliage. The fresh waters of the world are populated with about 800 types of branchiopods, including many microscopic water fleas. Some fairy shrimps live in brackish tidal pools. These pools fill and empty with the changing tides of the lunar month. This provides the natural drying out periods that the eggs require before they hatch.