Scott Snyder. photo by Tim Fitzgerald

Charting the Unknown

by Teresa Gleason

He's the Indiana Jones of the parasitic world.

Scott Snyder, an associate professor of biology at the University of Nebraska at Omaha (UNO), is on a crusade of sorts.  His evolutionary parasitology lab on the UNO campus is traversing the globe in search of new species to collect and classify.  The goal, he says, is to determine the incredibly complex life cycles of these creatures and examine their evolutionary relationships through the use of molecular techniques.

His second-floor lab in Allwine Hall is an interesting amalgam of "old" and "new" basic science.  On one bench, traditional dissecting microscopes are used to recover parasites from their animal hosts.  Slides drying on nearby slide warmers await examination under compound microscopes that magnify specimens up to 1,000 times.  On another bench, a thermocycler is used to amplify small amounts of DNA into millions of copies, which are then examined on special gels and processed through additional chemical reactions.  Across from the thermocycler, an automated DNA sequencing machine decodes the processed DNA.

The lab's human inhabitants are part artisans, part historians and part geneticists.  "We do everything from identifying new parasites via microscopy to DNA sequencing and manipulation," he says.  "The use of genetic sequences is exciting because it allows us to examine relationships from the distant past and understand the current parasitic world in much more detail than we can using traditional methods alone." 

Dr. Snyder is the recent recipient of a $295,000 grant from the National Science Foundation's Biodiversity and Inventories Program, which supports research into unknown aspects of the planet's biodiversity. 

His work focuses on the parasites of Australian freshwater turtles, which currently represent five major divisions, or phyla.  Of the 39 recognized species to date, 20 have been described since 1994.  "Although this relative explosion in taxonomic activity would seem encouraging, in reality, it merely highlights how little we know about this fascinating fauna," he says.

In support of this theory, Dr. Snyder reels off the following statistics:

All 20 species described since 1994 are from the same phylum.  In addition, these parasites represent only seven of Australia's 25 turtle species.  Most were collected in or before 1994, and most were collected from southern Queensland or northern New South Wales.  "In short, a brief period of activity that examined only one of the five phyla of turtle parasites in a restricted geographical area more than doubled the number of known species," he says.

In June of 2004, Dr. Snyder traveled to Australia to begin work on his theory that a large amount of turtle parasite diversity has yet to be uncovered.  His examination of only two snake-necked turtles collected in the Mary River, Northern Territory revealed eight parasite species.  Six of these species, Dr. Snyder says, are new to science, and at least one belongs in a novel genus – the taxonomic category ranking below a family and above a species.

During the same month, Dr. Snyder collected three Victoria River turtles from the Victoria River, Northern Territory.  The trio hosted six species of parasites, five of which he classifies as new and two of which he says represent novel genera.

"My examination of a mere five turtles increased the total number of parasite species recovered from this region from one to 15, the number of parasites recovered from the snake-necked turtle from zero to 8, and the number of parasites recovered from the Victoria River turtles from zero to 6," he says.

The new National Science Foundation (NSF) funding will allow Dr. Snyder and his colleagues to travel the Australian continent to determine if parasite diversity in Australia is similar to that found in the United States.  Both land masses are similar in size.

Dr. Snyder, who grew up in southeast Nebraska and graduated from Auburn High School, noted that collecting specimens in Australia poses a number of unusual challenges.  First and foremost is the saltwater crocodile of northern Australia, which lives in rivers alongside the turtles that are the subject of his research.

"These crocs reach up to 18 feet in length and are happy to eat humans if given the chance," he said.  

On land, Australia is home to more poisonous snakes than anywhere else in the world.  Add this to the fact that Dr. Snyder works in incredibly remote areas, and the combination can be lethal if extreme care is not taken.  "If you get bitten, there's no chance of making it to a hospital in time," he said.  "It's a beautiful, uninhabited place, but its dangers make you change the way you do biology."

At the conclusion of the grant, Dr. Snyder and his colleagues - including Vasyl Tkach at the University of North Dakota – hope to describe as many as 100 new species. Tkach also received a grant for $185,000 from the NSF's Biodiversity and Inventories Program.  These yet-to-be-discovered parasites, never before seen by another human being, will be returned to the UNO lab for microscopic examination and DNA analysis by Dr. Snyder and his student research assistants.

Natalie Black, a first-year student at the University of Nebraska Medical Center, said working in Dr. Snyder's UNO lab as an undergraduate helped her obtain scholarships that are putting her through medical school.  "He pushed us to think for ourselves and to be scientists, not just students," Black said.  "Working for him helped me gain an excitement for science and its practical applications."

Black said she valued Dr. Snyder's practice of taking his students to scientific meetings.  "This was huge in helping us enjoy and be proud of the work we were doing and gave us another reason to want to work hard," she said.

Dr. Snyder also collaborates with a number of researchers from the United States and around the world to examine questions of parasite systematics, evolution and biodiversity.  These collaborations all draw information from host and parasite life histories, DNA sequences, morphology and biogeography.

His work to date has shown that some of the turtle parasites he's discovered are related to schistosomes, parasites that infect more than 200 million people in tropical areas.

"At any given time, 2 billion people on this planet are infected with a parasite," Dr. Snyder said.  "Of this number, 500 million are infected with malaria, which kills between one and two million people each year.  By understanding the general pattern of parasitic evolution in a broad and diverse range of animals, the potential to better understand how parasites affect humans increases.  Labs like ours are the first rung on that ladder of understanding."

For more information about the evolutionary parasitology lab at UNO, contact Dr. Snyder at 402.554.2469 or sdsnyder@mail.unomaha.edu, or visit the Web at http://avalon.unomaha.edu/parasite/.

Teresa Gleason is director of communications at UNO.  She can be reached at tmgleason@mail.unomaha.edu.