Monday, March 19, 2012

OBJECT #5: A land planarian

    I have a very boring-looking terrarium sitting in my basement workshop.  It’s looks like it has nothing in it but some dirt, stones, leaves, and chunks of bark.  However, hidden under some of the rocks are some very bizarre creatures.  Last fall, during our “Simple Invertebrates” unit, I brought in some containers of dirt from my garden to use for a scavenger hunt.  The kids were given magnifiers and were told to find as many forms of life as they could.  Of course, they all found earthworms (some of them almost microscopic-- it is easy to forget that worms start out very, very small!), little gray “pill bugs” (or “rolly-pollies,” or whatever those little armadillo-like arthropods are called in your region of the world), and a selection of tiny millepedes, centipedes, spiders and insects. 

    Then one student found something amazing (and a bit alarming, as it turned out).  She called me over to looked at a strange worm she had found.  As soon as I saw it I was pretty sure it was not in the same family as the earthworm.  Its body was not segmented.  It was also too large to be a round worm.  As I watched it under our stereo-microscopes, I saw it extended its head far enough that the shape of the head became visible.  It was flat!  The head was round and flat, like a plate. I suspected that we had found a land planarium.

    As soon as I got home from my class, I began searching the web for pictures that matched what we had found.  It was definitely a land planarian, a terrestrial “cousin” of the famous freshwater planarian that regenerates body parts.  Cut a planarian’s head off and it will grow a new one.  Split its head down the middle and it will grow two heads.  Cut it lengthwise and each half will grow into a complete animal.  Planarians are very handy in biology labs that study tissue regeneration.  (You can get them from science supply companies like Carolina Biological. I had ordered some for this unit and the kids had a great time watching them slither around their jars.  I highly recommend them.) But this planarian lived on land, not in the water.

    I read some articles on land planarians and learned that what I had found was a recent invasive species.  These planarians are not native to North America.  They most likely had come over from Indo-China, hitching a ride on tropical greenhouse plants that had been shipped over.  Before they got to America, they had been discovered invading England.  They were first found in greenhouses at Kew Gardens in 1878, thus their scientific name, Biplaium kewense, and their nickname, the “Kew worm.”  They have been in America since 1901, but have stayed mainly in greenhouses.  But now they are on the loose.  Maybe mine came from potted plants I had bought from greenhouses and planted in my garden.

    I began looking around my property to see if I could find another of these rare flatworms.  To my surprise I found lots of them hiding under rocks or bricks in soil that was very damp.  Land planarians “breathe” by absorbing oxygen through their skin and they must have a layer of moisture around them to do this. Very wet clay seemed to suit them perfectly. 

    More research revealed that land planarians eat earthworms.  They’ve been known to tackle earthworms that are larger than they are.  And unfortunately, land planarians don’t till the soil.  They don’t harm the soil, but they don’t benefit it, either.   If the population of land planarians begins to increase and the population of earthworms begins to decrease, we could see the health of our soil declining.  So basically these weird little things are invaders we don’t want in our gardens.  Great-- I’ve probably got hundreds of them already.  My excitement about my discovery was gradually turning to horror.  These things should not be in my garden.  But how to get ride of them?  Researchers are still working on this problem.

    I found a website that tracks where these critters are showing up. They have been found in quite a few US states, but not all of them.  Apparently they have some really huge ones out in CA.  I prefer the tiny PA ones.

    I’ve lived in Pennsylvania most of my life and I’ve never seen one of these.  I guess I just got lucky on one of my trips to purchase to a greenhouse to buy plants.  Some people win the lottery.  I got land planarians.

Here’s one of the articles I read:

(The close-up picture of the planarians was taken with my new Panasonic Lumix DMC-ZS8 camera.)

Tuesday, March 6, 2012


    How many of you have a TARDIS in your basement?  Okay, how many of you know what a TARDIS is?  My UK readers are laughing right now.  Shocking but true, a surprising small percentage of Americans know what a TARDIS is.

    TARDIS stands for Time And Relative Dimensions In Space.  Time Lords use these things to zip in and out of time and space, meddling in the affairs of other planets and galaxies.  Only.. there’s just one Time Lord left, and we don’t know his real name.  We just know him as Dr. Who.  He’s Britain’s only superhero.  Dr. Who is as popular in Britain as Harry Potter is in the US.

    I’m not a hardcore “Whovian” because I haven’t seen ALL the old episodes from the 1960s, 70s and 80s.  PBS would run them late at night, and on the weekends, so I didn’t get to see very many of them.  The first time I got to watch the show with any consistency was when my two oldest children were very small.  It was a special treat to watch an “adult” show (funny how in America it was young adults who watched it, not kids) after the kids were in bed.  But I never made it to the end of a show.  I would inevitably doze off as the plot thickened.  My brain would then incorporate the sounds of the show into my dreams and I would be off chasing aliens half the night.

    I’ll never forget watching the first episode of the new-and-improved Dr. Who (written by Russel T. Davies) in 2005.  I was stunned.  The show had been completely regenerated into something that a body could never fall asleep in front of.  By this time I had kids old enough to watch along with me and we were all addicted by the end of the first episode.

    At first it was very hard to acquire the episodes.  The show had not caught on yet here in America and the only way we could get it was to rely on copied CDs that a friend very kindly burned for us.  When the next CD was dropped into our hands, we revered it as gold.  We’d make a big family night of it, with popcorn and soda and snacks.  Then somehow the parties started to grow with friends dropping in.  (And fortunately we found a way to torrent the episodes.) By the time we got to season 4, we’d have up to about 18 people at our gatherings.  And the menu grew, too.  Now, Dr. Who nights often involve full dinners.

    Then one day last summer, I decided we needed a TARDIS at our gatherings.  It had to be thin so it would fit against the wall as a decoration and could be stored easily in the garage.  But it also had to look 3D enough not to look like a large poster.  So I gathered some wood scraps, bought a few more, and started cutting and gluing.  The feature I am most proud of is the light fixture at the top.  I used a plastic peanut butter jar, a lid from a sports water bottle and a mayonnaise jar lid.  I cut them in half (lengthwise, so the fixture is flat on the back) and used epoxy to glue them together. I installed a nightlight bulb inside so the light really works.

    I think I painted this thing blue about 10 times.  I had purchased several shades of blue acrylic paint and did lots of experimental mixes.  Then I’d compare my results to photographs of the TARDIS.  I was somewhat relieved to discover, after a bit of Internet research, that the exact shade of the TARDIS had changed of the years.  So I couldn’t be all that wrong no matter what shade I used.  But I wanted my shade to be not-too-bright, not-too-dull, not-too-purple, not-too-gray.  After the final coat of paint I added a coat of matte finish so that the paint would be protected but without making the surface too shiny.  Shiny surfaces make photography difficult and I knew that one of the primary purpose of this prop was to provide a backdrop for some fun photos.  The final touch was the installation of some speakers in the back so it can make the famous TARDIS landing noise.

    I was fortunate enough to be able to travel to London a few years ago right when there was a big Dr. Who exhibition going on.  We got to see the original props used for the show (but not the TARDIS).  However, they didn’t need a TARDIS at the exhibition, as where was a permanent one on the street not too far from the convention center.  I wonder how many London natives have given directions to visitors using this TARDIS as a landmark?  It does stand out a bit!