I spent the summer of 2021 working in a lab studying Schmidtea mediterranea, a deeply silly model species. Here is me in the tank room:
(the shirt was a gift from my sister but I think its ultimate origin was tumblr circa 2014)
I had taught myself to crochet a few months earlier, so I started crocheting S. mediterranea bookmarks. Lots of them. Our coffee table was covered in them.
It wasn't until months later that my roommate saw a picture of S. med for the first time and went "wait their eyes actually look like that??? I thought you were just trying to make them cute!"
If you have a few S. mediterranea and want some more, there are two ways to get them: breed them (the worms are hermaphroditic and lay eggs), or cut them into pieces. If you cut an S. med into five pieces, given enough time and food you will have five worms, and they will all be young and fertile even if the original was too old for eggs.
HOWEVER! There is a strain of S. med that lost their reproductive organs. In any normal species this variant would go extinct, but these worms just started ripping themselves in half. Once an asexual worm reaches a certain size, it anchors its tail to a rock or the aquarium glass and tugs until the end of the tail falls off. (I don't know why they do this. My thesis failed to reject the null hypothesis and the only conclusion is that my fine motor skills are insufficient for benchwork.)
Despite being "immortal under the knife," flatworms are really picky. The big tank in the basement was our main stock, but if you're doing an experiment you keep a tupperware of worms and springwater upstairs in the lab. If you clean the tupperware (a process that involves pipetting water at worms in the corners until they slide off so you can scrub) too often or not enough, or feed them too much beef liver purée, then the water becomes TERRIBLE and MOLDY or TOO CLEAN or UNACCEPTABLE IN SOME WAY NOT DETECTABLE BY HUMANS and your worms start wrinkling up and dying. Then you have to check your flatworms under a microscope and get rid of the ones that aren't flat anymore.
One day, when I had committed some kind of Worm Sin against my Worm Bin, I put a wrinkly worm under the microscope expecting to see tissue damage and instead saw something so weird I had to build it out of construction paper for you:
Yes, that is an entire second head folded up between the worm's eyespots. The worm is fine. Planarians have incredible regenerative capabilities--that's why we study them--but if they get nicked or injured or for no reason at all they sometimes "regenerate" extra heads and tails. This was not my first two-headed worm, just the weirdest.
Planarians don't really age, but if you keep one alive for a long time without cutting it the odds of something like this happening go up. One time, a lab tech asked me if I had ever seen our alternate species that we keep for comparison experiments. I said no, so he brought out a tupperware and focused the microscope on what he said was a "good one":
GAK! (That species wasn't supposed to have seven heads, this worm was just old and bored I guess because we never did anything with the alternate species.)
I miss the worms, but mostly I miss the people. That lab had the best workplace culture I've experienced to date. When our first grad student successfully defended her thesis, we threw a very over the top party for her in a conference room, complete with homemade caramel-and-pecan planarians. Even group chores were fun.
I don't want to get my PhD or become a professor, but if I did, I'd want to be the professor who led the worm lab. If anyone who worked with me that summer sees this, thank you and I hope you're doing well!
