I was so excited for today's blog post that I tweeted about it last night when I was leaving work. I also called my mom; she didn't answer because she was out with a friend, but it was worth it for the extremely fitting text exchange we had afterwards.
That's right - last night, I acted as lab assistant for Christina Bergey while she searched through some bear guts on the hunt for tapeworms. Many of you will probably have reactions similar to my mom, and after last night I don't really blame you.
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I'd like to share with you today some of our experiences from last night. Why? Because sometimes your career in a research field will lead you down some pretty bizarre paths. While your paths might not necessarily be as smelly as the one we took last night, or the one I took in my Garage Lab, you come to appreciate how many unique opportunities you'll have as a research scientist. If nothing else, they all will make for incredible stories one day.
Warning: A lot of the images that follow in this blog post are just gross, and I realize that some of you (like the bear in the gif below) might not want to see photos of bear guts and contents. Therefore, most pictures are shared as links you can click on at your own risk.
You may be wondering why Christina was sifting through bear guts looking for tapeworms. We in the Perry Lab have been sequencing the genomes of various tapeworm species, some of which infect humans. A candidate for the closest relatives to some of the human infective species are found in the small intestines of bears, and good samples of these bear worms are very rare -- there's only one set of known samples from North America in a museum. If we could get a sample of these particular bear worms (Taenia arctos), we'd be able to find out more precisely how the human-infective form has changed.
Only a few references to T. arctos exist, but two are listed here if you're into reading about that sort of thing:
- Catalano, S., Lejeune, M., Verocai, G. G., & Duignan, P. J. (2014). First report of Taenia arctos (Cestoda: Taeniidae) from grizzly (Ursus arctos horribilis) and black bears (Ursus americanus) in North America. Parasitology International, 63(2), 389–391.
- Haukisalmi, V., Lavikainen, A., Laaksonen, S., & Meri, S. (2011). Taenia arctos n. sp. (Cestoda: Cyclophyllidea: Taeniidae) from its definitive (brown bear Ursus arctos Linnaeus) and intermediate (moose/elk Alces spp.) hosts. Systematic Parasitology, 80(3), 217–230.
Tapeworm Life Cycle
From Stephen Johnson et al's 2015 AAPA Meeting poster presentation
"The tapeworm lifecycle starts in a definitive host [A] (typically a carnivore) with a G.I. adult tapeworm infection [B-C)] shedding eggs into the environment via feces [D]. An intermediate host [E] (typically an herbivore) then ingests the eggs and develops larval cysts in muscle [F] and organ tissues. Tapeworm cysts lie dormant until raw or undercooked tissue is consumed by a definitive host, propagating the cycle anew."
We have previously analyzed DNA sequences from the species of tapeworm featured in the phylogenetic tree on the right.
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Upon acquiring the aforementioned bear guts a few weeks ago, we chucked them in the freezer so we could work out a plan for dealing with the intestinal materials in a responsible and safe (and hopefully not too smelly) way. After thawing the guts in a sink, Christina worked with them in a fume hood (AKA literal lifesaver). Christina wore a rather stylish ensemble for this work, featuring an organic-filtering respirator and lab coat. Time to get sifting.
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And I mean literally sifting, with a sifter. Christina would grab a chunk of intestine, cut it open with scissors, then feather her fingers along the tissue to feel out the worms. She'd rinse the intestines in DI water to see past all the poo, then pull any potential worms out onto a stainer.
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All in all, Christina was *probably* successful in this most peculiar of treasure hunts. DNA has been extracted as of this morning, and we'll prepare libraries to send out for sequencing next week so we can verify the species. Fingers crossed for Taenia arctos!
Thanks for reading! Share your #dirtysciencejobs with us, we would love to hear them :) Cheers!