Forest Preserve District of Cook County, Illinois
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Nature Bulletin No 552-A   February 1, 1975
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

Here in the Middle West we are a thousand miles from the Gulf of Mexico where the shrimp boats haul their nets. Once a rare delicacy practically unknown in the average American home, the shrimp has become one of the most common sea foods on our inland markets. In cities and towns and along highways we see dozens of neon signs advertising "French Fried Shrimp". This has come about because rich new shrimping grounds have been found where American fishermen with their improved otter trawls can scoop up this "pink gold" on a large scale. And, gold it is, because they receive 65 million dollars or more annually for their catch -- more than for salmon, tuna, oysters or any other sea food. Annually Chicago wholesale dealers, alone, distribute more than 15 million pounds of shrimp tails.

A favorite pastime along the coasts of our southern states is to catch shrimps at night with casting nets. They jump like grasshoppers and their eyes glint orange by reflected light. Few of us northerners have ever seen a whole shrimp, much less a live one, because commercial fishermen pinch off their heads as they are caught. Actually the "head" of a shrimp is much more than a head. This shell-encased head includes the internal organs, as well as the attachments for the legs, eyes and other forward appendages, and the very long antennae or whiskers. This leaves only the meaty tail and a part of the intestine called the "vein". The shell is very thin and, in life, translucent with faint tinges of blue, green or gray. Only after they have been boiled do they turn "shrimp pink".

The shrimp is a crustacean related to the crayfish, lobster and crab. Like them it has five pairs of legs but, unlike them, the first pair is not an enlarged pincer or heavy claw. In water, they have three means of locomotion: walking or climbing with the legs, darting backward by flipping the scoop-like tail, or gliding slowly forward by the rhythmic paddling of several pairs of swimmerets under the tail. They feed on dead plant and animal matter.

Adult shrimps of different kinds range in body length from a little over an inch to eight inches or more. Most species live in salt water or brackish water, but a few kinds live entirely in fresh water. The females of these latter kinds carry their eggs under the tail as crayfish females do. These hatch into young that look like miniature replicas of the adults.

Infant shrimps of marine species, in contrast, get no parental care and go through a long series of transformations before they are the least bit shrimp-like in appearance. The female of the common edible shrimp releases enormous numbers of microscopic eggs -- a half million to a million of them at a time -- in the waters of the Gulf. These develop into tiny mite-like larvae that drift at the mercy of ocean currents and suffer enormous losses at every stage. At first they have unsegmented bodies, a single simple eye and three pairs of rudirnentary appendages. With each succeeding molt, new appendages are added until there are nineteen pairs in all, the body becomes segmented, and it gets the two compound eyes typical of adult crustaceans. Only a few reach the nursery ground near shore where they grow rapidly. When nearly mature they migrate back to sea and make the final change into full- blown shrimps.

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