When Bryn Mawr’s biology department was looking for a new laboratory lecturer, they hoped to find someone who could help change the introductory biology lab from a somewhat traditional, structured environment featuring experiments with predicted outcomes to one that might better reflect the sort of work an advanced researcher does…all while still teaching students necessary core concepts.
Enter Jennifer N. Skirkanich and the tiny worms called planarians.
As reported in a news release from the university, developmental biologist also interested in improving pedagogy, Skirkanich was studying early embryonic development in tadpoles as a graduate student when an article in the journal Science on planarians caught her attention due to similarities with her own research.
Planarians are non-parasitic flatworms ranging in size from about a 16th to a quarter of an inch and are found throughout the world. They 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 future Nobel Prize winner Thomas Hunt Morgan, whose work in the 1890s, along with the work of Harriet Randolph of the biology department, led to much of 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, ‘Ok, 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 the planarians to observe the natural regeneration process, Skirkanich has Bryn Mawr students feed the worms food containing double-stranded RNA to stop genes from being expressed, resulting in a host 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. 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,” says Skirkanich.
The charm of Skirkanich’s little critters has extended beyond her own lab. This fall, an ecology class led by 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. Right now we’re just calling them Bryn mawricus,” says Skirkanich, who is already thinking about a future planarian lab that might look at the interplay of ecologic factors and gene expression.
“Our second semester of intro bio is not focused as much on the cellular and molecular level but more on the organism as a whole: development, evolution, ecology, and physiology. We’re not working with planarians this particular semester but there’s no reason we couldn’t in the future,” says Skirkanich.
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,” says Davis. “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 memorable and meaningful learning experience.”
First-year students Wenzhi Song and Anna Bezruki agree.
“I did not expect my introductory biology lab to include opportunities nearly as interesting as those provided by the planarians,” says Berzuki. “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.”
“All the excitement and fun I had in the lab helped put concepts I’d learned from lectures into an interesting and memorable context,” adds Wenzhi.
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