Lamprey

Lore & Background

Lampreys are jawless fish with elongated, scaleless bodies that resemble eels, the largest species reaching a maximum length of about 1.2 meters. They lack paired fins and possess a single nostril atop the head, with seven gill pores on each side. Their defining feature is a toothed, funnel-like sucking mouth used for attachment. The common name likely derives from Latin meaning "stone licker." Adults have one pair of regular eyes and two parietal eyes (a pineal and parapineal), though members of the family Mordaciidae are an exception. Juvenile lampreys have poorly developed eyes covered by translucent skin, while adult eyes are well developed, accommodating by flattening the cornea to push the lens toward the retina. The brain is divided into the telencephalon, diencephalon, midbrain, cerebellum, and medulla. The buccal cavity allows suction attachment to stones or prey, enabling the tongue to rasp algae or tear flesh. Lamprey teeth are made of keratin and other proteins, with hollow cores for replacement teeth growing beneath. The last common ancestor likely fed on blood and body fluids of fish after metamorphosis, using three horny plates on the tongue to scrape through surface tissues. Some species evolved to feed on both blood and flesh, while others specialize in flesh, sometimes invading internal organs; flesh-feeders have smaller buccal glands. Lampreys are found in coastal and fresh waters across most temperate regions, with some species traveling significant distances in the open ocean. Their larvae have low tolerance for high water temperatures, explaining their absence from the tropics. Distribution is adversely affected by river habitat loss, overfishing, pollution, and dams, though artificial channels have created new habitats, notably in North America where sea lampreys became a significant introduced pest in the Great Lakes.

Reader's Guide

Lampreys are significant as one of the only two living groups of jawless fish, the other being hagfish, and their genetic relationship helps clarify early vertebrate evolution. Their unique anatomy—including a cartilaginous skeleton, a toothed sucking mouth, and multiple eye types—provides insight into the transition from jawless to jawed vertebrates. Ecologically, lampreys play varied roles: some are parasitic on fish, while noncarnivorous species do not feed as adults. Their distribution is affected by habitat loss, overfishing, pollution, and dams, but artificial channels have also created new habitats, as seen with sea lampreys becoming an introduced pest in the Great Lakes. Lampreys are valued as food in some regions, and their climbing ability is studied to design ramps aiding reproduction. The reduction of pollution in the Thames and River Wear has led to recent sightings in London and Chester-le-Street.

Did You Know?

• The common name 'lamprey' may derive from Latin lampetra, meaning 'stone licker' (lambere 'to lick' + petra 'stone'), though the etymology is uncertain.
• Lampreys have been described as the only living vertebrates to have four eyes: a pair of regular eyes and two parietal eyes (pineal and parapineal), except members of Mordacia.
• Lamprey teeth are made of keratin and other proteins, with a hollow core to allow replacement teeth to grow underneath.
• The last common ancestor of lampreys appears to have been specialized to feed on the blood and body fluids of other fish after metamorphosis.