The adult lampreys of some species are parasitic, sucking the blood of other fishes. The horny teeth, set in the circular, jawless mouth, attach to the prey and the lamprey feeds as it is carried along. Lampreys have an anticoagulant in the saliva that keeps the blood of the victim fluid. The parasitic sea, or Atlantic, lamprey, Petromyzon marinus, found on both sides of the Atlantic, has become well established in the Great Lakes, where it is considered a serious pest by the fishing industry. Many freshwater lampreys are not parasitic.
Lampreys resemble eels in external appearance and, although not related to the true eels, are sometimes called lamprey eels. When not attached to prey, they swim with undulating movements. The marine lampreys normally migrate into freshwater to spawn, and some populations have become landlocked in freshwater.
The sexes are separate in lampreys and fertilization is external. The parents die shortly after the eggs are deposited in a nest. The larvae, called ammocoetes, are about 1⁄4 in. (6 mm) long. They are transparent, eyeless filter-feeders and live in muddy river bottoms, eating particles of organic matter. Ammocoetes are used in zoology courses to demonstrate a theoretically primitive vertebrate construction. At about five years of age they metamorphose into the adult form. In some species the adult does not feed and remains the size of the larva.
Lampreys are classified in the phylum Chordata, subphylum Vertebrata, class Hyperoartia, order Petromyzontiformes.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
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