Native, possibly giant, earthworm science in the Pacific Northwest is advancing with the discovery of two new specimens from opposite sides of the interior Columbia River basin.
University of Idaho soil scientist Jodi Johnson-Maynard, an associate professor in the College of Agricultural and Life Sciences, said an earthworm that was most likely a giant Palouse earthworm was found in early March near Moscow.
Another earthworm specialist also considers a worm collected from private property near Leavenworth, Wash., as most likely a giant Palouse earthworm. That worm was sent to the Idaho scientist by landowner Lee Matthews of Seattle late last fall.
In both cases the worms are natives but damage either before or during their discovery prevented formal identification to the species level.
The Palouse native worm’s giant moniker may be under challenge. The two experts Johnson-Maynard consulted for the identifications questioned the giant designation because most specimens measure less than a foot long.
In late March, university agricultural and life sciences researchers working south of Moscow found two pieces of a native white earthworm totaling about 2 inches long while digging to study soils on a Palouse Prairie remnant.
The color and internal organs within the worm show it is a native earthworm, possibly Driloleirus americanus, the species known as the giant Palouse earthworm, Johnson-Maynard said.
Despite the name, the specimens of the giant earthworms found in recent years have measured less than a foot in length. Some reports indicate the worms can reach 3-feet long.
The discovery of the newest specimen occurred on the property of Wayne and Jacie Jensen south of Moscow as agricultural and life sciences researchers were collaborating on an invasive weed study by weed scientist Tim Prather to protect prairie remnants.
Support scientist Karl Umiker and undergraduate student Eric Robertson, an environmental science major from Wyoming, were studying soil properties in a remnant patch of Palouse Prairie on Paradise Ridge.
They found part of the worm in a soil sample but did not recover the entire worm, precluding identification to the species level, Johnson-Maynard said.
The Jensens grow wheat and other crops and maintain one of the largest privately-held remnants of the Palouse Prairie on their farm. They said the discovery was hardly a shocker.
“It was no surprise to us that they found the worm there,” Jacie Jensen said. “It’s an intact, functioning ecosystem of Palouse plants so the worm was where it should be.”
The Jensens use the prairie remnant as a source of seeds for a native plant and seed business, Thorn Creek Native Seed Farm, they started in recent years. They collect small samples of seed there, then grow the offspring to produce seed for sale.
The recovered portion of that worm was brought back to Johnson-Maynard, who then sent it to Sam James, a University of Kansas earthworm specialist, for DNA testing. James has another preserved earthworm of the genus Driloleirus that he used to compare to the Idaho worm. The genus includes the Palouse earthworm and giant Oregon earthworm.
The results of DNA testing will allow James to better interpret the history and relationship between the two Driloleirus species.
James completed the most recent assessment of the Northwest’s native earthworms in June 2000 as part of the federal Interior Columbia Basin Ecosystem Management Project.
James reported two more Northwest-native earthworm locations far west of the Palouse. He found one specimen, a close relative but no giant, near Beacon Rock State Park near North Bonneville, Wash. The other, identified as a giant Palouse earthworm, was found by another expert near Ellensburg in central Washington.
The Leavenworth native earthworm fits with that earlier report. Matthews of Seattle said through the years he has found dozens of large white earthworms in the spring or fall when the soil is moist. His 20-acre property is forested with ponderosa pines.
“It seems like I’ve found a couple a year since I bought the property in 1991,” Matthews said. He found the specimens while either while walking or digging and came across a worm in mid-November 2007 that he sent to Johnson-Maynard for identification.
She in turn sent the damaged worm to Michael Westwind-Fender, an Oregon-based expert on Northwest earthworms who has found several Palouse earthworms through the years. He said the worm was most likely the Palouse species, but damage to the specimen prevented confirmation as such.
What’s in a name? Scientific names consist of two parts, the genus (Driloleirus) and the species (americanus). The genus refers to a group of closely related species while the two names together designate a single species. Driloleirus americanus is the only native earthworm species recorded from the Palouse region.
The fragments found this spring near Moscow lack the internal structures required to determine the exact species, Johnson-Maynard said.
With damaged or incomplete specimens, as frequently happens with soft-bodied organisms like worms, it is often only possible to determine the genus because additional structures and details are required to identify the species.
The earliest known report of the giant Palouse earthworm dates back to 1897 when a scientist collected a specimen and referred to the worms as being abundant in the Palouse region.
During the past 30 years, at least seven specimens, either confirmed or preliminarily identified as giant earthworms (species of the genus Driloleirus), have been reported from isolated forested and non-forested locations throughout the Columbia Basin.
In 2005 University of Idaho graduate student Yaniria Sanchez-de Leon found the first specimen in nearly 20 years while sampling earthworms in a Palouse Prairie remnant owned by Washington State University on Smoot Hill near Albion, Wash.
Johnson-Maynard, a soil ecologist specializing in macroinvertebrates, plans to expand her earthworm sampling efforts this spring through a contract with the Idaho Conservation Data Center in the Idaho Department of Fish and Game and in cooperation with the Washington Department of Fish and Wildlife.
The discovery on Paradise Ridge occurred in an area that Johnson-Maynard had sampled in the past, illustrating that collecting giant earthworms is challenging. She will employ specialized sampling and preservation techniques to obtain specimens that can be determined to the species level.
Most earthworms found in Northwestern gardens and lawns originated in Europe, arriving on plants or in soil shipped to the New World. Very few worms found in the Northwest are native species.
The three native earthworm specimens analyzed by Johnson-Maynard since 2005 are the only natives she has seen from the Columbia River Basin since she joined the university’s faculty in 2000.
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