This Invasive Vampire Fish Is Helping Researchers Understand the Human Nervous System in Jaw-Dropping Ways The sea lamprey looks like it’s from another planet, but this ancient creature has a surprising amount in common with humans A sea lamprey shows off its nightmarish mouth. NOAA Great Lakes Environmental Research Laboratory via Wikimedia Commons under CC By-SA 2.0 Key takeaways: Sea lampreys and research Sea lampreys have large neurons and synapses, making them ideal for neuroscience research. Scientists study the creatures to learn more about how we might recover from spinal cord injuries. With a suction-cup mouth and over 100 teeth, the sea lamprey has earned the nickname "vampire fish" and comparisons to sea monsters. Sea lampreys are one of the world’s most ancient fish species, killing prey by latching their suction-cup mouth onto a fish's skin and rasping away the fish's flesh with a rough tongue to feed on blood and bodily fluids. Sea lampreys sound like something from a horror movie, but the creatures have been crucial to almost two centuries of neuroscience research. Neuroscientists study sea lamprey spinal cells, which the animals can regenerate if their spinal cord is damaged, as a model to understand the human nervous system, spinal cord injuries and neurological disease. The evolution of human brains and nervous systems is also closely tied to these alien-like creatures. Neurologists and zoologists began studying lampreys in the 1830s, examining their nerve cells to understand how the spinal cord works. Lamprey research took off after 1959, when biologists first described lampreys’ ability to regenerate spinal cord neurons and eventually swim after spinal damage. Sea lampreys are ideal for neuroscientists to work with because the animals have large nerve cells and synapses, making observation easier than in other species. “The synapses are so big that you can see them, and you can record from them and access them very easily,” says Jennifer Morgan, neuroscientist at the University of Chicago’s Marine Biological Laboratory. The creatures also have a similar molecular and genetic toolkit to humans, she says, which can make it simpler to translate research from lampreys to humans and find tools that work in both species. Lampreys thrive in different types of water, all over the globe. “[Lampreys] have been found on every continent except for Antarctica,” says Morgan, whose lab uses sea lampreys for research. “So, they’re very hearty animals and super easy to maintain.” The sea lamprey (Petromyzon marinus) filter feeds as a larva but becomes parasitic once it reaches adulthood, latching onto fish and feeding on their blood. They can feed on trout, salmon and other large, commercially important fish, and one sea lamprey can destroy up to 40 pounds of fish per year. Much of the supply of sea lampreys for research comes from the Great Lakes, where lampreys wreak havoc on the fishing industry. Although the species is native to the Atlantic Ocean, improvements in the late 1800s and early 1900s to canals connecting Lake Ontario and Lake Erie to the ocean enabled lampreys to bypass Niagara Falls, which had previously been a natural barrier. From there, lampreys invaded the lakes, where they have no natural predators. By the 1960s, lampreys had devastated trout fisheries in the region and a control program began to weed them out using pesticides. Sea lampreys’ invasion of the Great Lakes has actually boosted their use in research. Over the last century, the Great Lakes Fishery Commission has directed considerable amounts of research funding toward lampreys, to study their life cycle and how to eradicate them. This put more lampreys in labs, resulting in studies on other aspects of their anatomy and evolution. Collectors catch wild lampreys in the Great Lakes, says Morgan, and send them to the lab in coolers. “Great Lakes fisheries harvested these lampreys, and they wanted scientists to understand them more,” says Robb Krumlauf, developmental biologist and scientific director emeritus at the Stowers Institute for Medical Research, who also researches lampreys sent from the Great Lakes. “They had a natural supply that they could give to those who are interested in the research.” Although lampreys look like they’re from another planet, they have more in common with us than it might seem. Lampreys branched off from other vertebrates about 500 million years ago, so they have some of the oldest traits in the lineage: they’re at the base of the vertebrate branch of the evolutionary tree. Because of this, studying lampreys’ genomes can clarify important evolutionary steps in the lineage—like when vertebrates developed jaws, or arms and legs. Sea lampreys survived multiple mass extinction events, including the asteroid 66 million years ago that wiped out roughly 80 percent of life on Earth. “It’s a chance to have a glimpse of the past. It’s sort of like a living fossil,” says Krumlauf. Krumlauf studies how sea lamprey evolution and human evolution are related through how our faces and heads develop. The brain region that shapes facial and cranial features is similar across vertebrates, from lampreys to chickens to mice to zebrafish, even though all these animals’ heads look quite different. “There’s a common toolkit,” says Krumlauf. “If you have building materials, and they’re all the same, you can build a garden shed or you can build a mansion––what’s different is the way the blueprint is put together.” Studying lampreys shows how these blueprints evolved in the earliest vertebrates, says Krumlauf. His research links facial and head development in the animals to the development of craniofacial abnormalities in humans. The evolutionary history of lampreys and other vertebrates also helps scientists like Yi-Rong Peng, ophthalmologist and neurobiologist at UCLA, illuminate the evolution of vision. Peng’s research has found lamprey retinal cells are similar to those of other vertebrates, such as mice, chickens and zebrafish. Such a finding suggests retinal vision, like humans have, evolved early in the vertebrate lineage. Studying the overlaps between animal retinas gives a window into how vertebrates saw the world 500 million years ago. And understanding how the retina first formed in humans can help Peng’s research team study retinal cell degeneration that leads to blindness. Morgan’s lab studies how sea lampreys regenerate spinal cords, and its work could lead to advances that help humans recover from spinal damage. When researchers cut a sea lamprey’s spinal cord, it becomes paralyzed but can regenerate nerve connections. The process does not have to be perfect to work, adds Purdue University science historian Kathryn Maxson Jones. Lampreys’ original neuron connections don’t reform in the same way, but cells grow in flexible ways to compensate for damage––biology can take different routes to achieve the goal of a spinal cord that works again. And the large size of lampreys’ cells and synapses enable the research team to closely examine the whole process. A microscopic view of a sea lamprey’s reconnected spinal cord shows how it healed after being cut. Daniel Cojanu, Under Current Productions Sea lampreys are also crucial to Morgan’s research on Parkinson’s disease. A specific protein’s accumulation in the brain is linked to the progression of the disease, so injecting that protein into lamprey synapses allows the researchers to observe how it affects the nervous system. This gives insight into how the disease progresses in the human nervous system and how exactly neurons can recover. Scientists observe how damaged lamprey neurons regenerate and how many synaptic connections are restored, guiding how to target treatment in human brains. Morgan’s research team hopes to move from understanding nervous system damage in lampreys and humans to how to fix it. When you cut your finger and the area becomes numb, that’s because of damage to the nerve endings in the finger, which is part of your peripheral nervous system, explains Morgan. But you do eventually get feeling back, because humans can regenerate cells in the peripheral nervous system––just not in our central nervous system. But lampreys can. “When lampreys regenerate the spinal cord and recover function, they are using a lot of the same changes in gene expression that occur during regeneration of the peripheral nervous system in mammals,” says Morgan. “Why we can’t do that in our spinal cord is a big question. But I think learning from the adaptations of these animals, that can do these really neat feats of nature like regeneration, will tell you something about the recipe that needs to happen, the conditions that need to be met,” adds Morgan. And the parallels between lampreys’ brain features and ours make crucial research possible when studying human brains isn’t an option. “It often points us in the direction of things we would’ve never looked at in humans,” says Krumlauf. Get the latest Science stories in your inbox.

The sea lamprey looks like it’s from another planet, but this ancient creature has a surprising amount in common with humans