I think about snails and slugs a lot. They're usually the first thing I think about in the morning- due to the tank of freshwater snails in my bedroom. When I am walking along and I see a slug in my path, not only do I not think it's gross, I admire its strange texture and stalk-supported eyeballs for a moment or three. I usually relocate said slug to a safe location if I think it might get stepped on. I feel this group of critters is often overlooked, so I'd like to take the opportunity to share with you a few reasons that I like them.
Snail and Slug Basics
Snail and slug are general terms applied to many organisms. When using these terms, it really is quite simple to know which one is which. A snail is like a slug, but it has an external shell. A slug is like a snail with no shell. As far as taxonomy, similar-looking slugs and snails are not necessarily closely related to each other, there are many, many species. Both can be found on land, in the sea, and in freshwater. It's a diverse group, but they are all gastropods, a class of mollusks. Gastropod is derived from the belief that they move along on their stomachs (gastro= stomach, pod=foot), but nowadays the bottom part of them is referred to as a foot (see diagram below).
Snail shells come in so many different and wonderful forms. The snails and slugs themselves do too! And the tentacles on the front really do have their eyes on them. Cute!
It's not easy being a gastropod
Some days, there are so many slugs on the ground that I do not have time to admire and move them all. "Why are there so many of you now," I asked them one day, "and where do you go the rest of the time?" It turns out that slugs are very sensitive to being dried out, as you may have guessed, so they mostly only get in your way during or after rain. The rest of the time, they can be found under some wood, dense leaf litter, or other debris munching on vegetation, fungus, or meat! Snails have a bit of an advantage in this department, they can retreat into their shells to reduce evaporation until favorable conditions return. Some snails even have "doors" that they can shut to protect themselves.
Fun Snail Fact: Snails undergo a weird developmental process, the result of which is that their anus is right above their head. Apparently this makes it easier for them to fit into their shell.
Admittedly, snails and slugs sometimes cause problems for us. Invasive snails are a problem in Florida, and these "fast-moving snails" might be spreading a disease in the UK. But let's not let a few bad guys give the whole class of gastropods a bad name.
And the best thing about snails and slugs is the beautiful miracle of making baby snails and slugs. It is "beyond imagining," as David Attenborough says.
Not only are snails and slugs the coolest, they are an important part of the ecosystems they occupy. Different species cover a wide variety of ecological niches, including predator, prey, and decomposer. Decomposers are generally considered less glamorous, but they are absolutely critical to the functioning of the ecosystem. They take nutrients that are locked up in the remains of plants, animals and fungi, and make those nutrients available for new life.
That's all for today, but please leave a comment if you have a gastropod fact or story to share.