Wednesday, August 17, 2011

Surprising Slug Slime

   When I found a slimy slug eating mushrooms in my backyard, I thought the slug would make a good homeschool science lesson.  You can use the slug for a great introduction to the interesting field of chemical ecology and for a gratifying demonstration of the slug's chemical defenses.
   The slug's slimy defensive mechanism can be demonstrated by gently poking the slug with a toothpick or similar object. This photo shows the results of a slight poke...nothing surprising.
Slug Slime Experiment

But, this photo shows what happens when you wiggle the "toothpick" like you are an ant trying to get a bite of the slug.
Activating A Slug's Chemical Defenses
When the slugs chemical defenses "kick in",  the slime instantly coagulates into a gummy mass (slug slime glue) which can gum up the jaws of the attacking predators.
   In the photo above, I glued the "toothpick" to a board with the slug's coagulated slime.  Instant slug slime glue is a rather surprising result from poking a slug, isn't it?
    I enjoy reading Thomas Eisner's books.  Here is a quote from his book "For Love Of Insects" on the slug slime subject.
   "Biorationality told me also that the slugs themselves had to be protected, and I found that they did indeed have a remarkable way of coping with the likes of ants. There is a simple experiment anyone can do to activate this defense. Look for a slug, and when you find it, poke it gently with a toothpick. A pine needle or leaf stalk will do as well. As long as you keep the stick motionless, nothing will happen. But if you wiggle the stick, the slug will set in motion a coagulation mechanism, whereby the slime in the immediate vicinity of the contact point is converted into a rubbery blob that clings to the tip of the stick. The mechanism is wonderfully effective because it keeps an enemy from piercing the body wall or the slug. Ants are literally muzzled when they bite into a slug. They are thwarted the moment they bear down with their mandibles, and as they back away, are left with their mouthparts encased in coagulated slime.
   I still don’t know how the mechanism works but I can imagine that some sort or coagulation or macromolecular cross-linking is involved. Dan Aneshansley and I have data based on the response of slugs to localized application of mild electrical stimuli that show the coagulation to be triggered in a fraction of a second—literally in less time than it takes an ant to clamp down with the mandibles. And we have learned that in some slugs the coagulation is accompanied by the visible injection of crystalline material into the slime from specialized integumental cells."     page 397
  For Love of Insects by Thomas Eisner 
  If you homeshool, and you take your science lessons down the slug slime trail, the slug's ingenious chemical defenses are just one of the many interesting stops along the way.

 Here is a link for a site that has some experiments you can do with slug slime glue.

3 comments:

  1. That is very cool. Now I want to go find a slug.

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  2. Dana, we are inundated with slugs this year, so it's interesting to learn a bit more about them.

    Surprised by the GUN ad on your site -- but then I'm Canadian and we're not comfortable with hand guns.

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  3. Sybil,
    I'm not sure I've seen the ad you mentioned. I guess Google serves up the ads differently depending on location, etc.
    I should see if there is a way to help serve up ads that are more pertinent and useful to readers, i.e. an ad for a bug jacket like you mentioned some time ago, or perhaps some great pair of binoculars.

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