lampreys

Lampreys are a lineage of jawless vertebrates in the order Petromyzontiformes, part of the cyclostomes that also include hagfishes. They are eel-like fishes with a cartilaginous skeleton and a circular, suctioning mouth armed with keratinous teeth. They lack jaws and paired fins, and have seven pairs of gill openings and a single continuous dorsal fin extending to the tail.

Adult lampreys of parasitic species attach to fish with their round mouth and rasping tongue to feed on blood and body fluids. Nonparasitic species do not feed as adults. The larval stage, called ammocoetes, is burrowing and filter-feeding in freshwater sediments for several years before metamorphosis into a free-swimming adult.

Most lampreys are anadromous: eggs hatch in streams, larvae grow as ammocoetes in sediments, then juveniles migrate to the sea or large lakes before returning to spawn. Spawning takes place in gravel nests; after laying and fertilization, the adults generally die.

Distribution and impact: Lampreys are native to temperate regions of the Northern Hemisphere, including Europe and North America. Some species, such as the sea lamprey, have been introduced to new areas and act as parasites, affecting native fishes. Others are of conservation concern due to habitat loss, pollution, and barriers to migration.