Flatworms rock!

Really, they do. They rock so hard their backs no longer have any bone (to add the obvious witticism taken from a well-known expression).

I had a real fascination with planaria back in my religious but science-loving childhood. You see, in a decrepit dresser that stored junk in the family garage I came across the mouldering old college biology textbook of one parent. Neither parent was a biologist, or academic of any type; in fact, neither had finished college. (If they had done so, and learned more about the natural world and possibly about critical thinking, would they have resisted the pitch of the Jehovah's Witnesses years later? Who knows. But that's another story.)

While I don't recall either parent ever displaying a particular interest in biology, clearly one had taken a class or two. The book was awesome. Its name and author, I didn't note. And much of the college-level content was clearly above my reading level. But there was plenty that I eagerly read. I remember a few can't-look-away photos of cleft palates and other human deformities, and of course there was plenty of stuff about the reptiles and other animals I always loved reading about. Plus those diamond-headed flatworms with the crazy cross-eyed look, the planarians, recently in the headlines as scientists further tease out the secrets of their amazing regenerative abilities.

Take a planarian, said the textbook I found, cut it into pieces, and those pieces will regenerate into new flatworms. I already knew that an earthworm's front half could regenerate a lost back half, but the flatworms went one better: an amputated back half could regenerate a new head! Wow!

Wait, it gets better: Cut it into two lengthwise, said the book, and the strips will regenerate into whole worms. Zoinks! (Try that, annelids. I didn't think so.)

The madness didn't stop there. Split just the planarian's head lengthwise, and – this still blows my mind – the two flopping half-heads will each regenerate into a full head, creating a two-headed – but apparently perfectly healthy – freak. Bo-i-i-i-n-n-g!

All that was capped with the most stunning claim of all. Take a flatworm, teach it some simple lab behavior like shock avoidance, and cut it into two. When the pieces become whole again, both regenerated worms remember the behavior. Hold on; that's just the warmup. Here's the kicker: take a flatworm with learned behavior, grind it up and feed it to other flatworms, and the fattened cannibals acquire the behavior. Education via eating the smart! (Just imagine: that famous slogan "A mind is a terrible thing to waste" not as a call to support college educations but as an admonishment to clean your plate.) 

Well. You could hardly expect a proper youngster to be satisfied with mere black-and-white photos of awesome two-headed grotesqueries. I must have planarians of my own to mutilate.

Imagine my joy (yes, genuine joy) when I discovered these weren't obscure creatures living in deep-sea vents off of Madagascar or some such, but were there for the taking in the American Midwest streams where I was always on the search for snakes and frogs. Just turn over rocks in the stream, and if you really looked closely, little dark, fingernail-length flatworms were stuck to the underside of the rocks.

So I got a bunch of flatworms, an X-acto knife, and... well, I did my best to split heads down the middle, but it's not easy with no real equipment. The worms are small and they move. I managed to messily cut and/or crush some heads into a lopsided split, and tossed the patients into a jar along with pieces of planarians I had simply cut into halves or thirds (a much easier operation).

What happened? I wish I recalled the details better, but I can only tell you that I never saw any two-headed monsters. Or much of anything. The mutilated worms seemed to disappear, leaving nothing behind but a few floating bits of crud in the jar! Did they crawl out at night, drying up somewhere unseen? Did they die from problems with the water and quickly dissolve into soup? (I knew enough to keep them in their creek water, not tap water, but maybe the temperature was wrong or the water lacked oxygen?) Or did they – and this was the coolest possibility – eat each other, with only the last survivor's disappearance a mystery? (Yes, they were in pieces, but surely the pieces had some means of eating; how else would they gain the energy and mass for regeneration?)

I've no doubt that I could have solved the mystery with more experimentation, but I apparently lost interest and moved on to other shiny things. (That's why I don't blame my religious upbringing alone for my not becoming a scientist; clearly, I was also lacking the required persistence for science.) That leaves me wondering whether the amazing regenerating planarians also include escape artist secrets or even teleportation among their bag of tricks.

Okay, probably not. And in the years since, I learned that one of the more astounding flatworm facts doesn't hold water: Scientists have not been able to replicate the claim that planarians acquire the learned behaviors of fellow flatworms they ingest. The original results have been written off as observer bias (see Wikipedia entry). So, sorry, no gastrovascular mind-meld powers in our worms.

But hey, just because Wolverine doesn't have laser eye-beams doesn't mean he's not awesome. Flatworms still got lots, including the magic two-head trick. Planarians, my crazy diamond-headed pretties, I remain your number one fan.

(And now I'm curious, too. If you take a two-headed flatworm and split each of those heads, can you get a quadracephalo model? Just how far can we take this hydra creation? Hmm, just how sharp is my X-acto?)