March 29, 2001
A fatal case of indigestion: Ben Hanelt recently discovered the secret lifecycle of the horsehair worm.
Death to Crickets
Unraveling the Life Cycle of Horsehair Worms
By Tom Simons, Public Relations
To biologists, they have been one of the most enigmatic groups of animals in the world.
They're the horsehair worms of the phylum Nematomorpha, one of only four animal phyla known to be completely parasitic. They have been thought of as "enigmatic" because until last year, no one had a clue about their life cycle.
What has been known is that as adults, the worms are free-living in streams and lakes, where they gather to mate in tight masses that are almost impossible to unravel. It has also been known that the egg strings they produce become heavy, non-swimming larvae that settle to the bottom of the lake or stream.
The question has been how those aquatic larvae end up inside terrestrial insects such as grasshoppers or crickets, where they feed on the insect's internal organs and reach lengths of as much as 3 meters in some species before emerging to mate.
UNL doctoral candidate Ben Hanelt found the answer to that question in research performed in Lancaster County and at UNL's Cedar Point Biological Station near Ogallala.
"We found that these tiny larvae settle on the bottom of stream or lake and are taken up by almost anything in the water, and they produce cysts," Hanelt said.
Among the creatures that will ingest them, Hanelt found, are snails, fish and the larvae of aquatic insects like midges or mosquitos.
"Nematomorphs will encyst in midge or mosquito larvae and when the midge or mosquito larva emerges as an adult, the cyst is retained," he said. "When crickets or grasshoppers eat a dead midge or mosquito, they ingest the nematomorph cyst."
That, he said, proves to be a fatal meal for the insect. The nematomorph larva, which had ceased development when it encysted, emerges from the cyst and begins to eat the host creature from the inside out. When the larva finishes its meal, it emerges from the dead host as an adult, mates and dies. While crickets and grasshoppers aren't normally found in water (a necessary condition for the adult worm to emege), Hanelt said the speculation is that as the larvae near maturity, the insects become thirsty as well as weak and this can cause them to fall in the water.
In his research, Hanelt collected freshwater snails of a single species at 50 scattered sites in streams in Lancaster County and found nematomorph cysts in snails at 35 of the sites.
He fed some of the infected snails to crickets, waited 30 days and put the now-infected crickets in water.
"Within one or two seconds, the worms start emerging and in one case, nine worms 30 to 40 centimeters (12 to 16 inches) long and about 2 millimeters in thickness came out of one cricket," Hanelt said. "We weighed the worms and we weighed the cricket and they were about equal weight. So when the worms were done with the host, there wasn't much host tissue left."
Hanelt's research also showed that human population density and land use does not affect the distribution of nematomorphs. In fact, one of his collection sites was in a shopping center.
"As urban sprawl increases, the chances for human-worm interaction increases and some people or their pets may get infected," Hanelt said. "It's really a pseudoinfection because humans, dogs and cats really don't get infected the way a grasshopper would. It sure would make you sick - and there's reason to be concerned about that - but it's never been reported to be life-threatening."
Hanelt said although human infections are not common, about 150 cases have been reported in the scientific literature.
He said he has heard from people who found horsehair worms (so-called because of their resemblance to a horse hair that has come to life) in their toilet and feared a family member had been infected. "I ask them if they've recently killed a cricket and tossed in the toilet, and that usually turns out to be the case," he said.
April 6 Honors Convocation Recognizes Scholars, Teachers, Mentors
By Annette Wetzel, Public Relations
Twenty-five UNL faculty and staff members will receive awards for outstanding teaching, student advising or service, and more than 3,400 students will be recognized for outstanding scholarship at the 73rd annual All-University Honors Convocation beginning at 3:30 p.m. April 6. in the Coliseum.
Thirty-one seniors will be honored as Chancellor's Scholars for earning a 4.0 grade average during their entire academic career at the university and at any other post secondary institutions. They are: Jaclyn Anderson, math; Donald Arp Jr., history; Angie Child, biochemistry; Heather Easter, psychology & sociology; Katie Fraass, chemical engineering; Kiley Frank, political science & history; Kimberly Gradoville, chemistry & math; Kristyn Harms, agricultural education; Amy Hulme, bio science & bio chemistry; Charlsi Hulsebus, architectural studies; Gregory Krafka, economics; Stephani Krienert, biological sciences; Cynthia Lamm, communication studies; Amanda Maine, international studies, French, political science; Shane Mares, communication studies; Karen Meier, biological sciences; Christine Murphy, business administration; Courtney Niemeyer, elementary education; Nicholas Phillips, music; Heidi Redelfs, English; Mark Rentschler, mechanical engineering; Christina Riesselman, English & geology; Cari Roeth, communication studies; Megahn Schafer, management; Jeremy Scheffler, math; Jennifer Thomsen, management; Brandon Tomjack, criminal justice; Megan Torau, math & economics; Ruby Urban, administration; Amanda Wilcox, advertising & English; Angela Wild, bio system engineering.
A total of 393 seniors will be honored as Superior Scholars for being in the upper 3 percent of their colleges, or for being on the honors list since their matriculation as freshmen. An additional 958 freshmen, 679 sophomores, 768 juniors and 628 seniors will be honored as High Scholars for having cumulative grade point averages of 3.6 or higher.
Christin J. Mamiya, professor of art and art history, will receive the Annis Chaikin Sorensen Award for distinguished teaching in the humanities. This award carries a a $3000 cash award, provided by the Sorensen family.
The following faculty members will receive Distinguished Teaching Awards from their colleges. Each recipient will receive a $1,000 cash award, provided by the Nebraska Legislature. They are: Deborah Bandalos, associate professor, department of educational psychology; Diane C. Cawein, associate professor, school of music; Rochelle L. Dalla, assistant professor, department of family and consumer sciences; Joan L. Erickson, association professor, department of special education and communication disorders; Steve Goddard, assistant professor, department of computer science and engineering; Bruce B. Johnson, professor, department of agricultural economics; Craig M. Lawson, professor, college of law; C. William McLaughlin, senior lecturer, department of chemistry; Deborah Minter, assistant professor, department of English; Stephen D. Scott, assistant professor, department of computer science and engineering; Keng Siau, associate professor, department of management; Nicholas Spencer, associate professor, department of English; Alan E. Steinweis, Rosenburg associate professor, department of history; Sidnie White-Crawford, associate professor, department of classics and religious studies.
Stephen Mason and Daniel Walters, professors, department of agronomy and horticulture, will share the Student Foundation/Builders Award for Outstanding Advising. They will each receive a $750 cash award provided by the University of Nebraska Foundation.
Arnold J. Bateman, director of learning center coordination and assistant vice chancellor for extended education and outreach, will receive the Distinguished Educational Service Award. He will receive a $1,500 cash award, provided by the NU Foundation.
Mark R. Powell, assistant director of intramural sports and campus recreation, will receive the Chancellor's Exemplary Service to Students Award. He will receive a $1,000 cash award, provided by the NU Foundation.
William E. Splinter, the George Holmes University professor emeritus in the department of biological systems engineering, will receive the George Howard-Louise Pound Award for exceptional contributions through teaching, research, public service and administration. He will receive original artwork painted by artist and UNL faculty member Keith Jacobshagen.
Charles H. Adams, professor emeritus in the department of animal science, will be honored by the Nebraska Alumni Association with the Doc Elliott Award.
The following faculty members will be recognized for receiving University of Nebraska systemwide awards:
Daniel J. Bernstein, professor in the department of psychology, will be recognized for receiving Outstanding Teaching and Instructional Creativity Award. This honor carries a $3,500 cash award. Bernstein will also be recognized for the Scholarly Teaching Award.
Gary E. Moulton, professor in the department of histor, and Brett C. Radcliffe, professor and curator of insects with the State Museum, will be recognized for receiving Outstanding Research and Creative Activity awards. This honor carries a $3,500 cash award.
Ruth M. Heaton, assistant professor in the center for curriculum and instruction will be recognized for receiving the Donald R. and Mary Lee Swanson Award for Teaching Excellence with a cash award of $10,000.
The newly established Harold and Esther Edgerton Junior Faculty Award will be received by Chris Gallagher, assistant professor in the department of English, and Stephen C. Scott, assistant professor in the department of computer science and engineering. This first-time award establishes $3,000 in professional development funds and $1,000 cash award for two years.
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