Lamprey

Lampreys are special kinds of fish without jaws, belonging to a group called jawless fish. They are part of the order Petromyzontiformes. One of their most noticeable features is their toothed, funnel-like sucking mouth, which helps them survive. The name "lamprey" may come from a Latin word meaning "stone licker," though this idea is not completely certain.

There are about 38 known species of lampreys alive today, with three families classified based on where they live—two smaller families in the Southern Hemisphere and one larger family in the Northern Hemisphere. Scientists believe lampreys are more closely related to hagfish than to other fish with jaws. Fossils show that lampreys have been around for about 360 million years.

Most lampreys spend their early lives in a juvenile stage called "ammocoete," where they live buried in sediment and filter feed. Some adult lampreys are known for feeding on other fish by attaching to them and consuming flesh or blood, but only 18 species do this. Nine of these move from salt water to fresh water to breed, while others live only in fresh water. The remaining lamprey species do not eat as adults and live off energy stored from their juvenile stage.

Distribution

Lampreys live in coastal and fresh waters in most temperate regions. Some species travel far in the open ocean, which is why different groups don’t stay separated. Others live in lakes that are cut off from the ocean. Their young, called larvae, cannot survive in very warm water, so they are not found in tropical areas.

Lampreys face challenges from habitat loss, overfishing, and pollution. In Britain, lampreys were once found far up the River Thames, but changes in the rivers have affected their numbers. Dams and construction can block their paths, but new channels have sometimes created new homes for them, like in the Great Lakes in North America, where they have become a problem. Efforts to manage lamprey populations are being adjusted to protect drinking water.

Biology

Lampreys are a special group of fish without jaws, often called lamprey eels. They have a unique, funnel-like mouth with teeth and a long, slender body without scales. Adult lampreys can grow up to about 1.2 meters long, with the sea lamprey being one of the largest.

Lampreys have a simple brain structure and special eyes, including regular eyes and two extra eyes on the top of their heads. Their bodies are built differently from other fish, with a cartilaginous skeleton instead of bony vertebrae. They are excellent swimmers, moving efficiently through the water with special swimming techniques.

Young lampreys, called ammocoetes, live in soft sediment at the bottom of streams, where they filter feed on small organisms and particles. After several years, they undergo a transformation and become adults, ready to swim upstream to reproduce in clear, gravelly streams. Lampreys come in many species, each with unique markings and colors that help scientists identify them.

Fossil record

The oldest fossil lamprey, Priscomyzon, dates back to the latest Devonian period in South Africa, about 360 million years ago. Other early lampreys, like Pipiscius, Mayomyzon, and Hardistiella, lived during the Carboniferous period in North America. These ancient lampreys were smaller than today’s lampreys and had simpler mouths with fewer teeth. They might have eaten by scraping algae off other animals instead of feeding on blood like modern lampreys.

Later, around 163 million years ago during the Middle Jurassic period in China, Yanliaomyzon appeared. This lamprey had the specialized toothed mouth seen in modern lampreys and likely hunted like them. An even later species, Mesomyzon, from the Early Cretaceous of China, showed the three-stage life cycle of modern lampreys, including a larval stage called ammocoetes.

Lamprey and chordate synapomorphies

Certain characteristics are shared over evolutionary history. Organisms with a notochord, a dorsal hollow nerve cord, pharyngeal slits, a pituitary gland/endostyle, and a post-anal tail during development are considered to be chordates. Lampreys have these features, which define them as chordates.

Lamprey anatomy changes with development. The notochord comes from the mesoderm and helps the organism when swimming. The dorsal nerve cord rolls into a hollow tube during development. The pharyngeal slits are openings in the throat that help move water when feeding. Young lampreys feed by filter feeding, and as adults, they attach to other fish, using these slits to help breathe. The final feature is the muscular tail that extends behind the anus.

Use in research

Lampreys are important in research because their simple brains help scientists understand how early animals' brains might have worked. Researchers have studied lampreys for many years to learn about how muscles move and coordinate during swimming.

Lampreys are also used in medical studies. Their large nerve cells help scientists explore how messages travel between nerves. Even after serious injuries to their spinal cords, lampreys can fully recover. They also have a special ability to remove certain genes from their body cells, which might help us learn more about diseases like cancer.

Relationship with humans

Attacks on humans

Lampreys sometimes bite people, but they usually only do this if they are very hungry.

As food

Many people enjoy eating lampreys. The ancient Romans liked them a lot. During the Middle Ages, rich people in Europe often ate lampreys, especially during Lent, when eating meat was prohibited. In some places today, like Portugal, Spain, and Japan, lampreys are still a special treat. They can be cooked in many ways, such as grilled, smoked, or made into rice dishes.

However, the mucus on lampreys can be harmful, so it’s important to clean them well before cooking.

As pests

In the North American Great Lakes, lampreys have become a problem because they eat other fish that people care about. Special barriers and safe chemicals are used to control them, but it’s a difficult task.

In folklore

In old stories, lampreys were sometimes called “nine-eyed eels” because people long ago thought they had extra eyes. Different cultures have their own names and tales about these interesting fish.

In literature

Lampreys have appeared in stories and books over the years. For example, a character in a novel by Robert Harris is based on an old tale where a cruel man wanted to feed someone to his lampreys, but was stopped. Another story laughs at a man who cried over the loss of his pet lamprey.

In television

Lampreys were also shown in a TV show about history, where a character was killed by being pushed into a pool of them.