Wednesday 18 January 2012

Land Planarian

Image: Wikimedia
When I first saw the words "Land Planarian" I thought it was some kind of tiny, desktop greenhouse. I imagined tiny gardens and tiny jungles, tiny fruit on tiny trees and tiny leaves adrift on tiny rivers. I imagined a miniature wonderland of lush foliage right there on the living room table.

But then I saw one.

Land Planarians are terrestrial flatworms. They look pretty darn nasty, all sludge and slime. Someone must have gone round asking people what they hate most about slugs and earthworms and then just threw the results together in an effort to make the world's most despised animal. I'm sure an evil scientist is cackling malevolently somewhere as we speak.

Image Blackbone Music via Flickr
This may explain why so little is known about Land Planarians. They seem to be remarkably understudied, seldom spoken of and it appears that many have never heard of them at all. It's nature's dirty little secret. In fact, were anyone's dirty little secret given life and left to fend for itself, I think it'd look just like a Land Planarian.

Being flatworms, Land Planarians have no circulatory or digestive organs. Everything is done through diffusion, such that they have to be flat and simple in shape to ensure all their cells get everything they need. Land Planarians don't even have a way of keeping water in, so they can only live in moist environments to avoid drying out. For these reasons most flatworms are tiny, but the most ambitious Land Planarians can reach 60 cm (2 feet) in length!

Despite this incredible fragility and squirmy, worminess, Land Planarians are actually predators. Some eat soft things like slugs, worms (jealous of their dashing good looks, no doubt) as well as other Land Planarians. Others manage tougher prey, insects and the like. No plates or cutlery is involved and most lamentable of all, neither is a napkin.

A Land Planarian's best friend is a ghastly assortment of mucus. They follow mucus snail trails to sniff out prey, there's mucus to help them span wide gaps like Spiderman gone wrong, and then there's sticky mucus to entrap prey. Next comes the eversible pharynx, basically a throat that is turned inside-out and comes out of the mouth. This can be used to grab onto soft bodied prey, or cut into the exoskeleton of tougher fare. Glands then secrete digestive mucus to dissolve victims and create a meaty broth.

A small flatworm will have guts that are not much more than a sack. Larger ones will have a branching affair, all to ensure that every cell can absorb the nourishment as it washes by. Many don't even bother with an anus, they'll just pass waste out through the mouth. Others have one or several anuses. It seems to me that a 2 foot long flatworm probably wouldn't want to usher waste products all the way from the back to the front. Then again, I don't frequently ponder flatworm evacuation points.

It's horrible from beginning to end, but that's flatworms for you. I can't help but have a sneaking respect for something that looks so incredibly horrible, yet manages to get even worse when you learn more about it. Well done!

Image: Wikipedia



  1. No no nooo! I first though that this was just some algae because I had seen the photo at the bottom. Then I read about "everything done via diffusion" so I thought these are just harmless (albeit somewhat disgusting) worms, "eating" microbes through their skin and moving around veeery slowly and randomly.

    But no, these are disgusting "Spidermen"! They move around reasonably fast and are disgusting predators, scary as hell. I hope I never see one in person otherwise I will have nightmares for the rest of my life!

    P.S.: The Spiderman part was the worst. I think you should make a post listing all the scary abilities of monsters you have written about and let people vote for the worst one. I will definitely vote for slime abuse by land planarians!

  2. Your contact page doesn't work! I run, which has many of the same goals as your site, and thought maybe we could collab on something sometime :D

  3. Haha! That's the amazing thing with this animal, you just don't quite know where it fits in. It's so different from just about any other slug/worm thing.

    Thanks for that idea! Certainly something to think about!

  4. I kill about 10-50 of these nasty worms a night/early mornings. I grow plants so I NEED my earth worms!! Best way to kill these nasty things, get a squirt bottle and fill it with vinegar and pour 1/4 cup (or more) of salt in bottle and squirt them! Now the REALLY Gross part, when you squirt them they get whitish blister like things on them and if you touch w/stick or something they WILL Explode!! Haha.. Its Gross! When squirted it kills them instant!!.. Also vinegar will kill the earthworms as if trying to save the earthworms for your yard avoid the reg worms!!!!...i read from a guy who had 3,000 lbs of worms on his worm farm and hammered worms killed ALL his worms in 7 days!! That's alot of earthworms!!! Geezzz

  5. Wow! Sounds like they're incredibly hungry! And I suppose if they're so nasty in life it's no surprise they're pretty gross in death.

  6. You left out the coolest part: if you cut a flatworm into pieces (even little tiny pieces), each piece can regrow the rest of its body to become a genetically identical flatworm. Could this be the solution to world hunger?

  7. Hahaha! I think most people would find it difficult to see the flatworm as the answer to any hunger at all!

    If we could make a loaf of bread act like that, though...

  8. Invasive earthworms are destroying north american forests at an astonishing rate (specifically amythas agrestis), also invasive are planarian however they do nothing more than slow the deterioration of our forests. Sure eathworms are great for a garden, but those same reasons that make them so great make them the true monsters.

  9. BTW there is not a single native north american earthworm, all are invasive!

  10. Wow! I looked that up a little. I had no idea there was so much trouble from earthworms!

  11. I tried organic gardening for a few years, and earthworm and nightcrawlers population increased drastically. Thought it was a good thing right? But last spring I noticed piles of leaves and debri where I know I planted bulbs. Just a few weeks ago I saw a huge nightcrawlers eating a live leaf! These things have been dragging whatever they can find into the ground. Many of my bulbs didn't come up this year so I used bayer advanced. Now some things are beginning to sprout. Between them, slugs and earwigs my beautiful butterfly garden looked like winter was upon us in full force by july! Almost everything died. I've been looking for insecticides to kill the nasty things, since my butterflies never survived last year. Good to know there's a bug that will eat them! Now, how do I find them and bring them to my yard?

    1. Forgot to hit notify me button. Lol. If anyone knows how I can get them please let me know. Thanks!

  12. Just found one of these and killed it. I also need my earth worms for my plants and turtles.