February 2014 Archways

Meet Bryn Mawricus

Tiny worms reshape introductory biology lab.

By Matt Gray

No, it’s not science fiction. A host of mutant worms have wiggled their way into students’ imaginations and into science education at Bryn Mawr College. They came here courtesy of Jennifer N. Skirkanich, a lecturer in the biology department who is teaching the introductory biology lab this semester.

A developmental biologist who is also interested in improving pedagogy, Skirkanich was studying early embryonic development in tadpoles as a graduate student when she came across an article on planarians in the journal Science. These tiny nonparasitic flatworms, which are found throughout the world, have an amazing ability to regenerate themselves.

“Any part of them that you cut off, they can grow back,” explains Skirkanich. “In fact, the piece you cut off will grow back into an entirely new planarian. It’s really quite phenomenal, and in some species the growth can occur in just one week—making them ideal for use with students in the laboratory.”

Planarians are nothing new; in the 1950s and ’60s they were a staple of high school and college labs. In fact, one of the pioneers in using planarians in the lab was Bryn Mawr faculty member and Nobel Prize winner Thomas Hunt Morgan, whose work in the 1890s, along with the work of Harriet Randolph of the biology department, contributed much to the early understanding of the worms’ unique abilities.

However that early understanding was by today’s standards fairly limited and may explain why the use of planarians fell out of practice in most labs.

“I think educators started to say, ‘Okay, that’s really neat, but since other organisms can’t do it, what’s the educational or research value,’” says Skirkanich. “Well, it turns out that the reason these worms can do this is because about 30 percent of their cells are stem cells. That makes this organism a really terrific model to study how stem cells work. It also turns out that a lot of the genes that decide how stem cells behave in planarians serve similar functions in other organisms, including humans.”

In addition to dissecting planarians to observe the natural regeneration process, Skirkanich has her students feed the worms food containing double-stranded RNA to stop genes from being expressed, resulting in a variety of mutant phenotypes including planarians with two heads, multiple sets of eyes, or no head at all.

“For an intro-to-bio student, this is really visually striking and memorable,” Skirkanich says. “At the same time, these are complicated concepts that they’re mastering. This relationship of DNA, RNA, and proteins is at the core of the first semester of introduction to biology.”

First-year student Anna Bezruki ’17 agrees. “From being able to help design our own experiments to seeing the effects our interventions had on regeneration, it was an ideal first lab experience,” she says.

The charm of Skirkanich’s little critters has extended beyond her own lab. This fall, an ecology class led by Assistant Professor of Biology Thomas Mozdzer collected planarians in the water retention pond on campus.

“I have a suspicion as to what species they are, but we have yet to identify them,” Skirkanich says. “Right now we’re just calling them Bryn Mawricus.” She is already thinking about a future planarian lab that might look at the interplay of ecologic factors and gene expression.

Biology Department Chair Tamara Davis says Skirkanich’s lab is a perfect example of the environment students can expect at Bryn Mawr.

“One of the goals of laboratory-based classes is to provide students with the opportunity to explore biological questions for which we don’t necessarily have a specific, known answer,” Davis says. “We don’t want our students to complete a lab asking, ‘Did I get the right answer?’ but rather, ‘What result did I get, and how can I explain it?’ Open-ended labs such as the planarian lab allow our students to take ownership of their research, which provides a much more meaningful learning experience.”


















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