Why snail is more snail

Can you tell which animals are univalves, meaning they have one-piece shells like the snail? Which ones are bivalves two-piece shells? Skip to main content. Birth to 5 Teens. Why do snails have shells?

Recommended Reads. Cychrine beetles have specialized bodies for preying upon land snails. Fireflies are a well-known insect whose larvae consume snails. Vertebrate predators of snails and slugs include herptiles such as salamanders and turtles; shrews, mice and other small mammals; and birds, especially ground-foragers such as thrushes, grouse, and turkey.

With regard to ecosystem function, shelled land snails as opposed to slugs are important in calcium cycling. They glean calcium from their food, concentrate it in their shells that are made mainly from calcium carbonate, and pass it up the food chain as they are consumed by Predators.

Both shelled snails and slugs can generally be categorized as decomposers, though they play only a small role compared to other decomposition organisms.

Land snails do not move far over their lifetime, so they can be excellent indicators of site history and site conditions. Because shelled land snails have a high calcium demand, they are sensitive to calcium availability due to soils and plants. Site moisture and past land clearing or fire also strongly influence snail populations.

Two Helix pomatia edible snails from Russia CM with apertures closed by an opaque epiphragm. Photo by T. In most snails, the epiphragm is thin and clear, but in some species, the epiphragm can be thick and opaque Fig. During dry periods, snails can form an epiphragm over the aperture or they can make a tight mucus seal between the aperture edges and substrates such as a rock or plant.

The seal helps to retard evaporative water loss. Some snails in the desert remain sealed under a rock for years before a rainstorm wakes them. Coelocentrum gigas from Guatemala CM Land snails in drier areas tend to have relatively smaller apertures like the shell on the left. Shells pictured are 8 and 8. Snails of arid areas usually have a relatively small aperture Fig. The smaller surface-area-to-volume ratio reduces moisture loss through evaporation.

Just like you would lose less heat on a cold day with your parka zipped up and your hood cinched around your face, the snail loses less water with less of its skin exposed, as in the case of a smaller aperture. Land snails in drier areas tend to have greater change in direction of growth when reaching full size, allowing the plane of the aperture to make a closer seal with flat surfaces.

As growing snails approach their final size, many dip the direction of shell growth toward the shell base Fig. This results in the plane of the aperture making a tighter seal on a flat surface.