Insight into Stress Hormone Evolution Provided by Sea Lamprey Research

A stress hormone in the sea lamprey has been identified by researchers at Michigan State University, using the 500 million-year-old species as a model to understand the evolution of the endocrine system.

Corticosteroid hormones control stress response in animals with backbones, including humans. While scientists have learned quite a bit about these so-called stress hormones in most modern animals, little was known about the hormones' earliest forms in prehistoric creatures such as lamprey.

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Weiming Li, professor of fisheries and wildlife who helped lead the project, said: "By identifying 11-deoxycortisol as a stress hormone in lamprey, it allows us to better understand how the endocrine system in vertebrates evolved into the complex systems we see in humans today."

The hormone is the only one the researchers have found so far in the lamprey and Li said the researchers are hypothesizing that it may be the only corticosteroid hormone in the lamprey. Humans, in contrast, have more than 30 corticosteroid hormones.

Native to the Atlantic Ocean, sea lampreys are invasive species in the Great Lakes. They stay alive by attaching themselves to other fish, like salmon and trout, and then suck out the fish's body fluids. One sea lamprey can kill 40 or more pounds of fish.

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Li led the groundbreaking research that identified the pheromone male lampreys use to attract females to their nests to mate. He has made a synthetic version of the pheromone and is testing its effectiveness as a control for the destructive parasites. While the identification of 11-deoxycortisol likely won't directly help his lamprey control work, Li said this new discovery will bolster understanding on how the fish has successfully adapted since the Paleozoic Era.

Li said: "Most jawless animals similar to the lamprey didn't survive into the modern era, so they're not available for us to use as we strive to learn more about how human systems developed. The sea lamprey, a survivor, gives us a snapshot of what happened as vertebrates evolved into the animals we know today."