Lampreys mouths are their most distinctive feature. Photo by NOAA Great Lakes Environmental Research Laboratory

The fisheries biologist held up a small tank filled with sloshing water to show us the creature inside. A wormlike silhouette wiggled wildly around the tank. The children squealed with delight at this strange creature, remarking on their eel-like shape and fast, undulatory movement. This was a special day for our Junior Naturalist Program. Some of our partners from the Wisconsin Department of Natural Resources had come to do an electrofishing demonstration for the children, and they caught a northern brook lamprey. 

Once, during a college field trip, I got to hold one of these creatures. The lamprey was slippery, wriggling violently between my fingers as they tried to slip out of my hand, but I managed to hold on. I didn’t know then, but I was holding something ancient. Lampreys as a group are very old. Their unique anatomical features place them at a pivotal point in evolutionary time. Undulating curled bodies and strange mouths tell us secrets about the past and future. 

To understand the lampreys’ story, we have to venture backward along branches of their family tree to the earliest living ancestors of fish, tunicates. Tunicates are vase-shaped, soft-bodied animals, who live most of their lives attached to rocks along the ocean floor. Their free-swimming larvae have many of the basic characteristics of fish, and are the animal right before lamprey in our understanding of how fish have evolved. 

There are no freshwater tunicate species, so you won’t see any in Wisconsin waters anytime soon. You may, however, see a baby lamprey, which is remarkably similar to a larval tunicate! Baby lampreys, unlike adults, don’t have eyes or teeth. After they hatch out of their eggs, baby lampreys burrow into the bottom of the river or lake they hatched in. These young lampreys will stay buried under the earth feeding on algae and microorganisms until they mature. 

The lamprey I saw with the children was not a juvenile. The small eyes peeking out at us made this fact obvious. After a minute, the lamprey began to settle, gently attaching its mouth to the side of the tank. This allowed the children to get a better view of a lamprey’s suction-cup-shaped mouth littered with rows upon rows of hook-shaped teeth. 

The lamprey’s mouth is one of their most distinctive features. Sharp teeth radiate out in circles around the opening. These teeth are not involved in breaking things down, but instead help a lamprey attach onto different things. Non-parasitic lamprey like the one we found quit eating once they reach adulthood, so their mouth is mainly used for carrying rocks to build their nests in the riverbed. 

Parasitic lampreys, on the other hand, use these teeth to attach to their prey. Once attached, the lampreys begin breaking through the skin of the fish. This is done with their tongue, which is covered in sharp teeth. When the skin is broken, they feed on the fish’s bodily fluids. The lamprey’s saliva prevents clotting and ensures a long meal.

This may seem gory, but lampreys are an important part of their ecosystems. The sea lamprey, which was accidentally introduced into the Great Lakes decades ago,  is the only one of our 5 species who has a negative impact. They feed on more fish than native lamprey and almost always kill their prey. Fish parasitized by native lampreys sometimes die due to the feeding wound becoming infected, but this does not have a negative impact on fish populations. 

As I shared some facts about lampreys with the Junior Naturalists, one of the fisheries biologists prepared to release our lamprey friend. None of the kids seemed particularly interested. They were content to splash around with nets, dragging them through the muck along the bottom of the river in hopes of making a catch of their own. One day they may regret letting the chance to hold something ancient slip through their fingers.

Sarah Montzka is about to start her senior year as a wildlife education major at UW Stevens Point. This summer, as a Summer Naturalist Intern at the museum, she taught our Junior Naturalist programs, assisted with live animal care and showed a real talent for finding and appreciating the oddest parts of nature.