Friday, December 18, 2015

Slug Life

In our search to learn all the living things on the preserve, we invite many experts that can identify the critters that most people don’t take time to look at.  This fall, Dan Dourson and his wife Judy graced this preserve with their enthusiasm about all things natural, and in particular, came to teach about land mollusks.  Now, we already had a nice collection of land snails from the preserve.  67 species of land snail have been identified on the preserve before the Dourson’s arrival. But after the class a couple species were added and a couple were eliminated from our list.  And they helped clear up some confusing species.  For example, we commonly find a  snail called the upland pillsnail, Euchemotrema fraternum,  but I had no idea there was also a lowland pillsnail, Euchemotrema leai.  Well there is a lot of them around, and there is a very subtle difference between the two.  Apparently I have been collecting lowland pillsnails for years and never knew the difference, which is a small hole under the “lip” of the snail at the umbilicus.  If this sounds confusing or foreign, see picture below or use Dan’s books clear all this up.
Notice the hole in the center of the snail under the lip of the lowland pillsnail on the left.  No hole on the upland pillsnail on the right.
But land snails aren’t the only land mollusk to be found.  We have been overlooking slugs, which can be found about anywhere on the preserve,  for as long as we have been identifying everything else.  So now, with the Dourson’s help, slugs shall not be overlooked from here on in.

One reason slugs are overlooked is because of the lack of resources available for identification.  And with what is available, slugs still are not an easy subject.  But lucky for us, Dan has written a few books that can be helpful to Ohio naturalists.  Kentucky’s Land Snails and Their Ecological Communities, Land Snails of West Virginia and Land Snails of the Great Smoky Mountains National Park and Southern Appalachians.  These books have most if not all of the snails and slugs that can be found in Ohio, especially southern Ohio.

So I wanted to try to use Dan’s Kentucky book to identify slugs that I come across.  That’s when this little creature appeared, on lettuce brought from the preserve Director’s garden.  Luckily, before   accidentally eating it, it made its way into the lab for further study.  From Dan’s book I learned that if a slug has a “saddle” on its back, it’s probably a non-native slug from Europe.  Apparently, most of the slugs we come across, especially in yards and gardens are exotic species.  This little slug had a saddle, but I found that there is one species of native slug possessing a saddle.  Unfortunately, it is virtually identical to a non-native relative.  Only dissection can determine the correct identification.  But since this slug was in a garden, near a dwelling with many exotic plants and soil brought in for gardening, it is most likely the non-native Deroceras panormitanum, the longneck field slug.  Under a dissecting scope with good light you could really see the markings and patterns of this creature.  With this view, the patterns matched up with the Deroceras species, and the size of the animal along with the position of the saddle helped separate it from other genera.

Deroceras panormitanum, the longneck fieldslug.  Notice the "saddle" on its back.

  I wanted to photograph this 22mm slug to send pictures to Dan.  I set up a piece of lichen covered bark to stage the slug about 2 feet off a table.  Watching this animal move is interesting to say the least.  The slime trail it leaves can actually be used to identify slugs, but mostly the color of its defense slime is used.  They use the slime for locomotion, defense and for antibacterial properties.  I assumed the slug would be stuck on this piece of bark for a while, seeing how slugs do not move too quickly, and it was high off the table.  But by the time I got the camera set up the slug was gone and on the table.   I was amazed to see how this slug made its getaway.  It did not crawl off the bark at all.....but it slime rappelled.  I had no idea a slug would use its slime to lower itself, like a spider on a web, to escape an uncomfortable situation. 

I put the slug on the bark a few more times, and every time I did, it tried escaping the same way.  Why waste time crawling when you can rappel to get away.  I’d never have guessed that picking up this one slug would be so educational. I guess that it produces the slime while it’s hanging in mid-air and slowly can lower itself to the bottom.  And if they can hang there for periods of time, I would imagine this could be a great retreat from predators.

Longneck fieldslug making its escape.

Slowly rappelling away.

Head first seems a bit dangerous, but that's a slug for you.

Arrived at the bottom, unfortunately for the slug it's a large table and could be re-captured.

Adding a few new species of land snail to our collection was what I was hoping for with the Dourson’s visit.  But now after collecting many different organisms over the years, I am most excited about having our first slug species added to the collection.  After all, they are everywhere.  I rarely lift a log in the woods without seeing a slug, why not know what species I am seeing.  A small start, but we now can say we definitely have at least these 4 species of slug:  Deroceras panormitanum  the longneck fieldslug, Arion subfuscus the dusky Arion, Megapallifera mutabilis the changeable mantleslug and Philomycus carolinianus the Carolina mantleslug.

If you would like to learn interesting facts about slugs like their practice of stabbing love darts into their partners while mating, their abilities to eat highly toxic mushrooms to beef up their defense mucous, slugs anti-bacterial properties that help humans or most importantly how to identify them and their snail cousins, check out Dan’s books mentioned and pictured above.   These books are not sold in stores or yet on a website.  To buy one you must reach out to him personally at 

Posted by: Mark Zloba