lamprey

Lampreys are jawless fishes belonging to the order Petromyzontiformes, an ancient lineage of cyclostomes. They have eel-like bodies, a cartilaginous skeleton, and a circular, suction-based mouth equipped with keratinized teeth and a rasping tongue. Lampreys typically possess seven gill slits and lack paired fins.

Most lampreys begin life as ammocoete larvae that resemble small worms, living buried in fine sediment and feeding by filtering microorganisms from the water. After several years, they undergo metamorphosis into juvenile and then adult forms. Some species become parasitic as adults, attaching to fish with their round mouth to rasp tissue and withdraw blood, while others are nonparasitic and do not feed as adults, dying after spawning.

Lampreys have a diadromous life cycle in many species, migrating between marine and freshwater environments. Spawning occurs in gravel nests in streams; females lay eggs, which hatch into ammocoetes that drift downstream or remain in the stream before reburrowing as larvae. Adults usually die after spawning.

Lampreys occur in rivers and coastal waters of the Northern Hemisphere. They are ecologically important as prey for larger predators and, in parasitic species, as predators of fishes. The sea lamprey (Petromyzon marinus) is a well-known invasive parasite in the Great Lakes, where it has caused declines in native fish populations. Control programs use barriers, trapping, chemical lampricides, and sterile-male releases to reduce populations.

Around 40 species are recognized within Petromyzontiformes, with varying ecological roles. Conservation status varies by species; habitat loss and dam construction threaten some populations, while others remain common.