Who named this snail the brown-lipped snail (Cepaea nemoralis)? Who notices the color of a snailโs lips, and who then compares the color of their lips to those of other snails? Do snails even have lips?
Well, yes, snails do have lips, or at least mouths โ on the underside of the head and thus hard to see. And as we all know, snails also have shells. The opening or thickened edge of the shell is called a lip. In adult brown-lipped snails, the lip of its shell is dark brown or even almost black. Hence, the name brown-lipped snail, which distinguishes it from a similar snail with a white-lipped shell.
The brown-lipped snailโs shell varies quite a bit. It can be yellow, brown, or even pink, with anywhere from zero to five bands. The brown-lipped snailis sometimes called the grove snail or the wood snail because it inhabits woodlands, but it also lives in gardens and grassy areas. In fact, it inhabits most any area with both shade and moisture. In its scientific name, Cepaea nemoralis, Cepaea comes from Greek kฤpaia, meaning โof the garden.โ And nemoralis is Latin, meaning โof the woods.โ These snails eat mostly dead plants, but they will eat leaves of dandelions and nettles. In general, they are not too much of a garden pest.
Where do I find these snails?
Brown-lipped snails are active in our region, especially on cool, damp days in spring and fall. Snail activity depends, however, on temperature and humidity levels more than on the calendar. Once sustained freezes arrive, they overwinter in sheltered spots and become dormant. In March and April, they re-emerge as temperatures rise. In hot summer weather, they estivate (a kind of dormancy). In October, look for them after it rains, under leaves and in your garden.
Brown-lipped snails, like many other snails, have both male and female organs and produce both sperm and eggs. They mate to increase genetic variation. Before mating, each snail tries to thrust into the other a sharp calcium carbonate spear (the same material as its shell) called a lip. Like most every other part of the snail, the dart is covered in thick mucus. The mucus contains a compound that, if it reaches the blood of the other snail, increases the spermโs chances of survival.
Only about half of love dart stabs are successful. Some miss completely; others do not pierce the skin. After the love dart attempt, the snails exchange sperm. Each snail acts as both male (donating sperm) and female (receiving sperm). Later, when the temperature, humidity, and food conditions are right, both snails produce eggs. The snails fertilize the eggs with their stored sperm โ often from several different snails.
The ancient Greeks observed snails and their love darts. Some people speculate that these observations led to the Cupid myth.
In New England, a brown-lipped snail generally lays eggs in late spring, summer or fall. First, it digs a small depression. How does a snail dig? Although it has no special digging appendages, it uses muscular contractions of its body to push into loose soil. It works its body into the depression, where it deposits 30 to 80 eggs covered in mucus (of course). It pushes soil over the eggs, which hatch in a few weeks. The young snails are miniature adults with small shells. The shells grow more spirals as the snail ages. In two to three years, the snails are mature adults with about five spirals and brown lips.
Brown-lipped snails are European, which means they are not native to the United States. People imported brown-lipped snails to New Jersey in the 1800s because of their colorful shells, which they thought would make a lovely garden addition. The brown-lipped snails in Massachusetts probably arrived from the Netherlands and Ireland on imported shrubs in the early 1900s. (Snail eggs and small snails are difficult to spot and remove in soil, mulch or other plant materials.) By the 1970s, these imported snails were common throughout the Northeast.
Brown-lipped snails have a great variety of colorful shells. Scientists often wonder why so many different shell colors persist over time, rather than one becoming dominant. However, shells in a given region may look similar for a couple of reasons.
Snail shells have a tendency to blend into their background in any given region. This likely occurs because birds see the snails that donโt blend in well and pick them off first, leaving behind the well-camouflaged snails. Over time, the camouflaged colors become more common in a region. Natural selection at work.
In addition, brown-lipped snails easily overheat. Snails that people imported to hot climates tend to have paler, more reflective shells, presumably because these shells absorb less heat, keeping them cooler and better able to survive. Over time, pale shells become more common in such regions. Conversely, brown shells absorb more heat and are more common in cooler regions. Studies have found associations between shell color, habitat and temperature.
Why so much mucus?
Snails produce lots of mucus because they have specialized cells in their skin that produce nothing but mucus. They use mucus to glide or climb, to prevent dehydration, as a defense against predators (slime can make snails difficult to capture) and for communication (snails follow slime trails to find mates).
Snail mucus acts as both a lubricant and an adhesive. How can this be? Snail mucus is a non-Newtonian material. This means its viscosity changes depending on the forces applied to it. If you have ever played with cornstarch mixed with water, you know that it flows when handled gently but hardens under sudden pressure. Snail mucus acts in the opposite fashion.
When a snail is stationary, the mucus behaves like a solid, gripping to prevent the snail from sliding backward. But when the snail produces muscular contractions with its body, the forces cause the mucus to flow, allowing the snail to glide forward. Snails crawl by using both of these properties. By producing mucus that both flows and grips, snails are able to move forward and even crawl up a fence or hang upside-down from a leaf.
The next time it rains, look for snails around you. They are easy to find. Just follow the visible slime trail. Notice the shell color and the number of bands. What snail colors do you find in our region?
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