University of Idaho Earthworm Research Turns Up Rare Find: Giant Palouse Earthworms

Tuesday, April 27 2010


Written by Bill Loftus

MOSCOW, Idaho – A project to understand earthworms and where they are found in relation to native plants and invasive weeds yielded a rare find in late March: several giant Palouse earthworms.

Shan Xu, a University of Idaho student studying soil science, and Karl Umiker, a research support scientist, found two giant Palouse earthworms on March 27. University of Kansas earthworm expert Sam James identified the adult on April 16 as a giant Palouse earthworm.

The second worm is a juvenile that is being kept in the Moscow laboratory for study and to provide DNA to help develop future identification techniques. In addition, Xu and Umiker discovered three earthworm cocoons during their sampling.

In the weeks since they were collected in the field and kept in the laboratory, two of the cocoons hatched and appear to be fast-growing giant Palouse earthworms.

"We are beginning to gain some understanding about where we are likely to find the giant Palouse earthworm, and how much we have to learn about them," said University of Idaho soil scientist Jodi Johnson-Maynard.

Johnson-Maynard's work focuses on earthworm ecology and nutrient cycling. The giant Palouse earthworms are an unusual feature of the native prairie she studies to better understand the ecology of how these sites function.

Native earthworms are a rarity in many areas. In a decade of soils and earthworm research at the University of Idaho, she and her team have found few native worms.

Researchers believe that introduced earthworms and other animals, plants and manmade changes including farming and community establishment and development have all influenced native worms. Little scientific information also exists about how common native worms, including the giant Palouse earthworm, were before settlement.

The confirmation of the adult as a giant Palouse earthworm will allow Johnson-Maynard to use DNA tests to identify the juvenile and worms found previously. It may also be possible to use soil samples to detect the presence of the rare natives in the future.

The most recent discovery followed the development of a new high-tech worm shocking probe that uses electricity to urge worms toward the surface, increasing the chance of finding worms in native Palouse prairie while minimizing disruption to its plant and animal life.

Johnson-Maynard studies nutrient cycling and earthworm ecology. She now ranks as the expert in one of the West's least known creatures, one that is discovered only rarely and then usually as fragments.

The worms in the laboratory appeared to dispel a couple of reports that added to giant Palouse earthworm lore: they did not smell like lilies, nor did they spit. And giant appears to be a relative term. The adult worm measured about 10 or 12 inches fully extended, the juvenile 6 or 7 inches. Rather than appearing white, the worms were more translucent, allowing internal organs such as blood vessels to appear.

Both juvenile and adult worms had pink heads and bulbous tails, rounded unlike the flattened tails on common nightcrawlers, the largest and perhaps best known non-native worm. The adult had a yellowish band or clitellum behind the head.

The giant Palouse earthworm was first reported to the scientific world in 1897. Few specimens were identified again until the late 1980s when James "Ding" Johnson, a University of Idaho entomologist, found two in a second-growth forest near Moscow while helping another graduate student search for insects.

The worms then escaped notice until 2005, when Yaniria Sanchez-de Leon, a University of Idaho graduate student studying earthworms with Johnson-Maynard found a specimen at Washington State University's Smoot Hill reserve near Albion, Wash.

She found the worm after it had been cut nearly in half as she was digging a hole to sample earthworms and soil. The worm was preserved and sent to Oregon-based Northwest native earthworm expert William Fender.

Umiker discovered the first intact adult giant Palouse earthworm in two decades while using the electronic worm sampler. After pulsing electricity through the soil, the juvenile crawled to the surface. The adult remained just beneath the surface, and Umiker used a trowel to dig it out.

A research focus on nutrient cycling, earthworms and invasive species led Johnson-Maynard and her graduate students to include intact Palouse prairie sites in their work.

In addition to the 2005 discovery, the University of Idaho researchers also found fragments of giant Palouse earthworms while sampling on a privately owned Palouse prairie remnant on Paradise Ridge south of Moscow.

The landowners, Wayne and Jacie Jensen, provide access to their property and its native prairie to scientists to support research they hope will help farmers produce better crops and improve their stewardship of the land.

“We are hopeful that the research on soils with the role of exotic and native earthworms, such as the GPE, will further our efforts to produce healthy food and in land stewardship in general,” the Jensens said in a statement.

“There is good science to be learned from the Giant Palouse earthworm and its habitats, for non-farmland and farmland alike," the Jensens added. "Our hope is that the pursuit to understand the very complex relationships between soil, microbes, plant and wildlife remains the focus.”

The giant Palouse earthworm has turned out to be a very complex story, and an exciting one for Johnson-Maynard and her team.

After the announcement of the 2005 discovery, another landowner near Leavenworth, Wash., reported finding a similar worm. In 2008, Johnson-Maynard received a sample from the landowner that was identified as a native earthworm, but was too damaged to narrow down to species.

With findings in prairie and woodland settings, much still needs to learned what is the GPE native habitat, Johnson-Maynard said.

A worm fragment found on Paradise Ridge in 2008 was too damaged to identify beyond being a native earthworm, although it appeared to be a giant Palouse earthworm.
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About the University of Idaho

Founded in 1889, the University of Idaho is the state’s flagship higher-education institution and its principal graduate education and research university, bringing insight and innovation to the state, the nation and the world. University researchers attract nearly $100 million in research grants and contracts each year; the University of Idaho is the only institution in the state to earn the prestigious Carnegie Foundation ranking for high research activity. The university’s student population includes first-generation college students and ethnically diverse scholars. Offering more than 130 degree options in 10 colleges, the university combines the strengths of a large university with the intimacy of small learning communities. The university is home to the Vandals, the 2009 Roady’s Humanitarian Bowl champions. For information, visit www.uidaho.edu.




About the University of Idaho
The University of Idaho helps students to succeed and become leaders. Its land-grant mission furthers innovative scholarly and creative research to grow Idaho's economy and serve a statewide community. From its main campus in Moscow, Idaho, to 70 research and academic locations statewide, U-Idaho emphasizes real-world application as part of its student experience. U-Idaho combines the strength of a large university with the intimacy of small learning communities. It is home to the Vandals. For information, visit www.uidaho.edu.