What’s smaller than your pinky nail, looks like a cross between a potato bug and a shrimp, and is only found in Portland waterways? Ramellogammarus similimanus — but you can call it “Stumptown scud.”

This tiny freshwater crustacean swims only in small tributaries and creeks in and around the City of Roses. When its existence was first widely publicized in 2017, Dr. David Shepherdson, a deputy conservation manager at the Oregon Zoo, said, “It is quite a special thing that Portland metro apparently has its own species that occurs nowhere else in the world.”

Researchers at Oregon State University received funding from the zoo at the time to study the minuscule creature, particularly to gather population insights — though it’s unclear whether those efforts amounted to any conclusive findings.

Researchers were using trace DNA in water samples to study Stumptown scud without catching or harming the fragile animals. | Photo by Michael Durham/Oregon Zoo

Stumptown scuds help keep Portland waterways clean by feeding on dead and decaying material. They also serve as a food source for fish, amphibians, and other aquatic predators. Fun facts: Females carry eggs in a pouch like kangaroos until they hatch and a cousin species — Ramellogammarus oregonensis — can be found elsewhere in Oregon and Washington.

Watch researchers collect water samples to study trace DNA left by the crustaceans.