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Natural History Of The Lamprey

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Science & Nature

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Lamprey is a common name for about forty species of jawless, eel-like fishes. They are very smooth skinned and scaleless. Some can grow up to three feet in length, usually only in the oceans. All lampreys are dull colored, ranging from light-tan to molted-brown or bluish-black. Scientist consider the lamprey to be one of the least developed vertebrates. The lamprey has no bony skeleton. It only has a backbone like notochord that is made of cartilage. The lamprey only has fins at the top of it. On each side of the body is a row of seven respiratory openings through which the lamprey breathes.
Adult forms of lampreys live on the blood of fishes and can sometimes cause serious depredations in fisheries. Their mouths are circular, without jaws and equipped with a piston like tongue that creates suction when the mouth is placed against an object, and the tongue is drawn back. In the inner part of the mouth and the edges of the tongue, there are many small, horny teeth. These are what the lamprey uses to pierce the flesh of fishes. The adult forms of lamprey die soon after spawning and reaching their mature form.
Lampreys mostly live in freshwater streams and seas of temperate and subartic regions throughout the world, except for Southern Africa. The sea lamprey is a marine species. They are native to the Atlantic Coast of North America and Europe. In many areas it has adapted to a life cycle spent entirely in freshwater. The sea lamprey invaded Lake Erie in the 1920's, where its warm water was good for reproduction. They migrated to Lake Huron in 1939 and then to Lake Michigan. Within a few years, the lamprey had severely damaged the valuable trout fish in these lakes. They were competing with the fishing industry for the available trout. After invading Lake Superior, the lamprey became a serious threat to the fishing industry there. As a result, in September of 1954, the United States and Canada signed an agreement for joint action against the lamprey. The most effective method of control was the electromechanical weir. This was where adult lamprey would get electrocuted as they swam upstream to go spawn. They also used selective chemicals to kill the larvae living in the bottom of the stream.
All lampreys breed in freshwater; usually clear streams with a sandy bottom. Marine lampreys swim up freshwater streams like salmon, passing rapids that get in their way. A special adaptation the lamprey has is that it sometimes attaches itself to a rock with its sucking mouth in order to rest or as an aid in moving through swift currents. Both male and female lampreys move stones with their mouths to make a shallow nest where the female deposits 62,500 eggs. As the eggs are laid the female stirs up sand so that it rises and weighs the eggs down. After spawning, which can only occur once in the lifetime of a lamprey, the adult lamprey will die within two to three months. The eggs hatch within two to three weeks, and drift downstream where they burrow in mud. The larvae are very different from the adult lamprey. They are blind and toothless, and have a different feeding mechanism. The larva is so different from the adult that scientists gave it a different name, ammocoete. The ammocoete remains in the mud for at least four years. It then undergoes a metamorphism into the adult form and goes to the adult habitat.
Lamprey is a common name for about forty species of jawless, eel-like fishes. They are very smooth skinned and scaleless. Some can grow up to three feet in length, usually ...

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