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With all the recent warm, wet days here lately, certain creatures have become more active. On our porch, I saw this four-inch slug sliming its way across a decorative rock we keep there (FIRST PHOTO). Missouri has quite a few slug species, but I'm pretty sure this is called a mantleslug.
What the heck is a slug anyway? Is it just a snail without a shell? Let's dig into this a bit.
The answer is a bit complicated. Slugs (as well as snails) are in a group of mollusks called gastropods. You might assume that slugs are a specific group of gastropods and snails are a separate group of gastropods. But that's not the case. There are several families of slugs, and the families are not closely related to each other. Each of these families includes some that have shells... which means those species are actually called snails.
Confusing? Let me put it this way: Each of these unrelated families of gastropods have some with shells, some without, and some with very small or internal shells. So, the feature of having no shell has evolved separately in each of these families.
The word "slug" is just a generic name for any gastropods without shells (or with reduced shells) and "snail" is a generic name for any that do have shells. Even if they are not related to each other.
THE SECOND PHOTO is a beautiful little sea slug that we found recently while snorkeling in Belize:
Another interesting gastropod we found while snorkeling was this flamingo tongue snail (THIRD PHOTO). These have a shell... but, interestingly, the pretty color and pattern you see is not the shell itself. Instead, this snail has living tissue, called the mantle, that extends out from the body and covers the shell to give it that striking pattern. When the snail is attacked, it can pull the mantle inside, leaving the plain white or yellow bare shell to protect it.
What the heck is a slug anyway? Is it just a snail without a shell? Let's dig into this a bit.
The answer is a bit complicated. Slugs (as well as snails) are in a group of mollusks called gastropods. You might assume that slugs are a specific group of gastropods and snails are a separate group of gastropods. But that's not the case. There are several families of slugs, and the families are not closely related to each other. Each of these families includes some that have shells... which means those species are actually called snails.
Confusing? Let me put it this way: Each of these unrelated families of gastropods have some with shells, some without, and some with very small or internal shells. So, the feature of having no shell has evolved separately in each of these families.
The word "slug" is just a generic name for any gastropods without shells (or with reduced shells) and "snail" is a generic name for any that do have shells. Even if they are not related to each other.
THE SECOND PHOTO is a beautiful little sea slug that we found recently while snorkeling in Belize:
Another interesting gastropod we found while snorkeling was this flamingo tongue snail (THIRD PHOTO). These have a shell... but, interestingly, the pretty color and pattern you see is not the shell itself. Instead, this snail has living tissue, called the mantle, that extends out from the body and covers the shell to give it that striking pattern. When the snail is attacked, it can pull the mantle inside, leaving the plain white or yellow bare shell to protect it.
Photo Credits:
All photos by Stan C. Smith
All photos by Stan C. Smith
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