Family Petromyzontidae

Lampreys

Selected Characters: Elongate, cylindrical shape; no jaws; disc-shaped mouth lined with keratinized 'teeth'; seven porelike gill openings; well-developed eyes; no paired fins.

This family of primitive jawless vertebrates is found in cool areas of the world. Lampreys live in freshwater or are anadromous; none are strictly marine. After hatching in freshwater, larval lampreys, called ammocoetes, burrow into the river bottom and filter nutrients from the substrate. While buried in the mud, ammocoetes undergo metamorphosis to the adult lamprey form, after which they emerge. Some lampreys then go through a parasitic phase, when they use the disc-shaped mouth lined with hard tubercles to attach to the body of a fish, rasp a wound in the skin, and feed on body fluids. In other lamprey species, the digestive system degenerates shortly after metamorphosis and the adult does not feed, but reproduces right away and dies shortly thereafter. These nonparasitic lampreys live exclusively in freshwater, while parasitic lampreys may be either freshwater or anadromous. North American lampreys have diploid chromosome numbers of 164 to 168 or more, the largest chromosome number of any group of vertebrates. There are 41 living species of lamprey. Two lamprey species can be found in Puget Sound, both of which are parasitic. Our largest lampreys grow to a maximum of 76 cm. Lampreys are moderately common in some areas of Puget Sound.

Puget Sound Species

Lampetra tridentata Pacific Lamprey

Lampetra ayresii River Lamprey