October 24, 2013
Yay, we just found flatworms in the Museum pond! You know, the worms that some of us (I'm not naming names) might have cut up with a knife in high school biology class. But don't worry! These worms are, "immortal under the edge of a knife." At least, that is how the noted flatworm specialist, John Graham Dalyell Esquire, described them in 1814.
An Immortal Worm, also known as a Planarian. Dalyell goes on to describe their regenerative capabilities, in his distinctive early 1800s prose: "Certain animals, though liable to perish by simple evaporation of their surrounding fluid, can, in other circumstances, endure privations apparently inconsistent with life itself. What prove deathly wounds to the majority of creation, only serve to awaken in them the active principle of an inexhaustible reproductive power. The perpetuation of their race is effected by means most remote from those that usually regulate the origin of animated existence. A shapeless fragment is disjointed from the body of the parent ; it remains in quiesence more resembling the state of death : but new organs are gradulally evolved—motion is resumed—and all the qualities successively displayed which belong to the primitive whole." Okay, so scientists thought planarians were cool in 1814, but are they still cool today? Well, I can think of at least six reasons off the top of my head. 1) They are a non-parasitic worm—which means they aren't going to burrow into our bodies and cause elaphantiasis of the nether regions! 2) They are hermaphrodites—they have both male and female sex glands—and they can reproduce asexually by fragmenting off parts of their body! 3) They are really easy to keep as pets! All you need to do is lure them out of their freshwater environs by dangling a bit of beef liver tied to a string (at least that is what the author of planarians.org did when he was a kid—sounds like my type of guy). 4) Not all of them live in water! There's a weird land planarian, Bipalium kewense, originally from Asia, that has been introduced into Los Angeles and can reach up to 18 inches in length. 5) You can buy a planarian mousepad. This 100% prooves they are cool! 6) Planarians can learn. When a planarian encounters a negative stiumli (i.e. hot temperatures or toxic chemicals) it will, when encountering the stiumui again, move away from it. Even cooler—when that planarian is cut into several pieces, the "new" planarians, in many cases, “remember” the learned response of the original planarian. Whoa! So, go out buy some beef liver and go "fishing" for planarians. Get to know them! And, since it's Halloween next week why don't you go and make yourself an immortal worm costume that'll be sure to impress all your friends. *Thanks to Richard Hayden, Head Gardener, for the photograph, and to Kirk Fitzhugh, Museum Curator of Polychaetous Annelids, for identification help.