Ralph Morris, age 13, of Brownsville, Tex., for his question:
HOW DOES THE SHRIMP REPRODUCE?
The shrimp is a slender shellfish that is related to the crab and the lobster. Various species of shrimp have different life cycles and different methods of reproducing themselves.
The most common kinds of United States food shrimp, the peneid shrimp, hatch from eggs that are laid in the ocean up to 100 miles offshore. A newly hatched peneid shrimp resembles a tiny pear with legs. It changes shape about 15 times until, after two to four weeks, it looks like an adult shrimp. A newly hatched shrimp of any species is called a larva.
Young peneid shrimp move toward shore as they develop, but 80 percent or more may be eaten by sea animals along the way. The survivors settle in bays and river mouths.
After about five to seven months near shore, the shrimp begin a two month trip back to deeper water. The males and females breed in deep water and then each female will lay betweeen 500,000 and 1 million eggs. Scientists believe that most of the adults die soon after the eggs are laid.
Some shrimp live only a year but others may live five years or more. Some females carry their eggs in their swimmerets until they hatch. Others lay their eggs and swim away. Some shrimp do not swim about but live in burrows that they dig in sand or mud.
Members of another important group of shrimp, the pandalids, all begin life as males. At about 2 years of age, they all change to females.
The United States leads the world in shrimp production. Louisiana, Texas and Florida rank as the leading shrimp producing states, in that order.
Fishermen from India, Japan, Thailand, Korea, Mexico and many other countries catch large amounts of shrimp. More than half of the world's catch comes from Asia.
Shrimp live in fresh and salt water in nearly all parts of the world. The smallest kinds of shrimp measure less than one inch long. Some giant fresh water species are a foot long.
Young shrimp eat plankton or small drifting plants and animals. Adult shrimp feed on material on the sea floor. Shrimp, in turn, serve as an important food for fish and other water animals.
The body of a shrimp has two main parts: the cephalothorax, or head and chest, and the abdomen. An unjointed shell covers the cephalothorax. A shrimp can bend because the shell of the abdomen is jointed.
Most shrimp have 19 pairs of jointed legs, feelers and other appendages. The cephalothorax has two pairs of feelers which taste the water to locate food; a pair of appendages that serve as jaws; five pairs of appendages that handle food; and five pairs of walking legs.
The abdomen has five pairs of fanlike swimmerets, which are used in swimming and reproduction. It also has a pair of appendages that form part of the shrimp's tail.