Food of Lampreys.—The lampreys feed on the blood and flesh of fishes. They attach themselves to the sides of the various species, rasp off the flesh with their teeth, sucking the blood till the fish weakens and dies. Preparations made by students of Professor Jacob Reighard in the University of Michigan show clearly that the lamprey stomach contains muscular tissue as well as the blood of fishes. The river species do a great deal of mischief, a fact which has been the subject of a valuable investigation by Professor H. A. Surface, who has also considered the methods available for their destruction. The flesh of the lamprey is wholesome, and the larger species, especially the great sea lamprey of the Atlantic, Petromyzon marinus, are valued as food. The small species, according to Prof. Gage, never feed on fishes.
Fig. 292.—Lamprey, Petromyzon marinus L. Woods Hole, Mass.
Metamorphosis of Lampreys.—All lampreys, so far as known, pass through a distinct metamorphosis. The young, known as the Ammocœtes form, are slender, eyeless, and with the mouth narrow and toothless. From Professor Surface's paper on "The Removal of Lampreys from the Interior Waters of New York" we have the following extracts (slightly condensed):
Fig. 293.—Petromyzon marinus unicolor (De Kay). Mouth of Lake Lamprey, Cayuga Lake. (After Gage.)
Fig. 294.—Lampetra wilderi Jordan & Evermann. Larval Brook Lamprey in its burrow in a glass filled with sand. (After Gage.)
Fig. 295.—Lampetra wilderi Jordan & Evermann. Mouth of Brook Lamprey. Cayuga Lake. (After Gage.)