Wednesday, June 10, 2009

Adirondack Slugs – Difficult to Love

What do you do on a rainy day when you have twelve wiggly pre-schoolers to entertain? You go looking for snails and slugs! These slimy creatures (the snails and slugs, not the pre-schoolers) can be difficult to find on days that are warm and dry, but bring on the rain, and the things practically come crawling out of the woodwork.

What is a slug, except a snail sans shell? Officially a mollusc, it is hard sometimes to reconcile a slug as related to oysters and clams. They may all be related, but on the family tree, slugs are definitely located on a twig of their own.



Most people really don’t appreciate slugs; after all, what’s to love about this squishy, slimy, oozing thing that eats your lettuce and other valuable plants? But, like so many unloved animals, if you really take the time to get to know them, you are likely to discover some fascinating facts.

For example, let’s take a look at slime. What purpose does slime serve? For one thing, it helps keep the snail from drying out as it crawls along the dry ground (assuming it hasn’t rained for days). It also soaks up moisture, another anti-dehydration strategy (and also the reason why the slime is impossible to wash off your hands/feet). Slug slime serves as an aid in helping slugs crawl over very sharp objects without sustaining any injury. Do you have your doubts? Go find a slug and set it to crawl over a sharp razor blade – a feat neither you nor I could accomplish! Some slugs use their slime to form a “rope” that they can use to lower themselves to the ground. A coating of thick slime can make a slug difficult to grab if you are a predator (think greased pig). Slug slime also acts like a map, leaving a chemical trail behind that the slug can follow back to its home.

Slugs (and snails) have tentacles on the front of their faces. On the slug, the two upper ones, which tend to be longer, also possess eye spots; these are the optical tentacles. These eyes are rather primitive, essentially sensing only light. The other two tentacles are sensory organs. As a matter of fact, much of the animal’s body is dotted with various sensory cells, although the majority are grouped around its mouth and tentacles.

Do you want a REALLY cool slug activity? Try this: find one good-sized slug and a piece of glass. Place the slug on the glass, lie down on your back, and hold the glass in front of your face so that you are looking at the slug’s belly/foot. After a few moments, the slug will calm down and start oozing its way across the glass. As you watch, you will see alternating bands of light and dark “roll” across the slug’s belly/foot in waves. These bands are caused by the muscle fibers on the slug’s belly/foot. Here’s what’s happening, according to the Field Guide to the Slug (put out by the Western Society of Malacologists): “There are actually two sets of these muscle fibers, each performing separate chores. To move forward, one set – those fibers directed inward and rearward – contracts between waves, pulling the slug from the front and pushing off toward the back. Simultaneously, the second set – the fibers directed inward and forward – pulls the outer surface of the sole forward, generating the pedal wave.” There’s a really good illustration of this on page 25 of this small volume.

Believe it or not, slugs are important. They are browsers, kind of like cows. They ooze their way along the forest floor sampling assorted fungi, lichens, algae, and soft plant parts. They will also eat other slugs, the odd insect or two, animal scats and carrion. In a way, they fill a vital role in the decomposition cycle of the forest. And they are constantly eating. And yes, slugs have teeth. Apparently their teeth are much like shark teeth in that they are continually being replaced. The teeth, however, aren’t used for biting off portions of food. Nope, that is done by a guillotine-like structure in the mouth. Once a piece of food has been lopped off, the slug applies uses its radula, a long, skinny body part that is covered with thousands of teeth (think rasp). It rakes this radula along the food, scraping it up and into the digestive tract. Makes you kind of glad that a)slugs are small, and b)humans are not on their menu.

Okay, so we’ve established that slugs are rather nifty, but even so, we don’t want them in our gardens, eating our plants. What can we do? Well, you can always go out with a salt shaker and sprinkle a bit of salt on any slug you find. This effectively dehydrates them and they die. Or, you can put out a dish of beer – the slugs crawl in, get plastered and die. Or you can put copper around your plants – apparently this causes an electrical charge to zap the slugs when they touch it. I’ve also read that putting wood ashes around your garden works fairly well: the alkali of wood ashes (the source of lye) is apparently an irritant to the slug’s mucus linings. But you also want to be sure you don’t get the wood ashes on your plants, for many plants also dislike a high pH.

Everything has a place in this world, and when everything is in its place, it is beautiful. Even slugs.

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Ellen Rathbone is by her own admission a "certified nature nut." She began contributing to the Adirondack Almanack while living in Newcomb, when she was an environmental educator for the Adirondack Park Agency's Visitor Interpretive Centers for nearly ten years.

Ellen graduated from SUNY ESF in 1988 with a BS in forestry and biology and has worked as a naturalist in New York, New Jersey, and Vermont.

In 2010 her work took her to Michigan, where she currently resides and serves as Education Director of the Dahlem Conservancy just outside Jackson, Michigan.

She also writes her own blog about her Michigan adventures.



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