Imagine you have to carry a shell on your back and that you're driven to eat the right foods to nourish that shell, and that some consider you a pest while others consider you food. Now take into account that you're so slow that anything that wants to eat you probably can -- you're not a fleet-footed evader of predators. Welcome to the life of a snail. You'll never find 100% agreement that they're cute, but there's no denying that their grim determination makes them at least a bit noble. (OK, that might be a bridge too far, but you get the idea!) Herein we take a look at some of these slow-moving critters. Of course, the shell is a snail's biggest show-stopper. They'll vary widely in color by species and are usually made of calcium carbonate, forming a spiral shape. To make a shell, snails use a bit of their own hardware called a mantle -- a thin, skin-like organ that secretes a liquid made up of shell material. The liquid hardens and forms the shell. Over time, the mantle releases yet more liquid, adding to the size of the shell.Snails Reveal Travels of Ancient Humans
Snails can be nearly invisible to the naked eye or reach more than 1 foot long. They're found in fresh water, salt water, and on land. They get knocked for their, well, snail-like pace, but it's not like snails can't move at all. Locomotion for most snails is by means of a large flat foot -- more like a body-length muscle -- underneath them that helps them glide across layers of mucus they secrete to smooth their way forward. It will even leave some slime in its wake, if you watch closely for it. You might be wondering
slow they are. Given it's football season, we'll use 100 yards as a metric. If a garden snail were to receive a kickoff in its end zone and return it all the way for a touchdown, you would have to wait about two hours to see it reach the other end and spike the ball. And garden snails are the absolute speedsters of the snail world!No Backbone? No Worries! Snail Makes Record First
Land snails will typically eat fruit, dead plants, some live plants, and even bark. Freshwater snails will feast on algae, dead marine life remains and plants, while sea snails enjoy algae as their main course. Snails have rows of small teeth that sit in long, tongue-like organs called radulas. They don't chew their food so much as grind and tear it with these teeth.Giant Snails' Health Risk Hype Matches Their Size
Snails have eyes at the ends of the longer pair of their tentacles. Land snails can zoom these up, down and all around while a sea snail's eyes are at the base of its tentacles and don't move.How Snails, Clams Are the Ultimate Survivors
Of course, food in the animal kingdom is often a two-way street: You're either eating or being eaten. A snail has plenty of things that would like to eat it, so that's where its shell comes in. If a predator like a snake or a bird is nearby, a snail can crawl in its shell and seal it off. It can stay holed up like that for days to weeks if it wants to.Escargot Could Follow the Dodo, Scientists Warn
Remember the mantle, the snail's organ that secretes material for the shell? Land snails breathe using a lung set into it. Sea snails, meanwhile, breathe through gills. Like fish, they use them to get oxygen from the water. Freshwater snails sometimes have gills, too, while others have lungs. When the latter need to breathe air, they surface and take a gulp.
Land snail eggs are not much bigger than a letter on your computer screen. Over a couple of days, a land snail will lay up to 100 eggs, burying them in shallow holes covered with dirt and their own slime. Most won't survive predation; those that do will hatch in 2-4 weeks. Sea snails will deposit their eggs by the thousands on the ocean floor, though most won't fare any better than those on land. Freshwater snails may deposit their eggs above the water line, such as those of the apple snail, shown here.
Unfortunately for them, some species of snail, such as abalones and some land snails, are eaten by people. France, for example, raises them for that purpose. (Snail fans who don't see them as food will want to avert their eyes from escargot.)
There are tens of thousands of snail species, found in a vast array of climates and habitats -- from suburban gardens to mountainous areas; from marshes to the deep ocean.Why Can't Humans Regenerate Body Parts?
Most snails are hermaphrodites, with both male and female reproductive organs. A mating ritual that can last several hours results in each snail having eggs to deliver, after they grow for a bit inside the snail. As we've seen, most young'ins won't make it, but a few will, and snails will find a way to keep on going.PHOTOS: Snails Used to Make Biblical Blue
The world’s strongest known animal teeth belong to aquatic snails known as limpets -- marine mollusks famous for their conical, tiny shells that resemble umbrellas.
The limpet's teeth, described in a new study in the latest issue of the Journal of the Royal Society Interface, are so tough and sturdy that they are now considered the strongest known biological structures on the planet, overtaking the prior holder of that record: spider silk.
"Limpets evolved strong teeth as the teeth scrape over rock surfaces every day to feed," the study's lead author Asa Barber, of the University of Portsmouth and Queen Mary University of London, told Discovery News.
"If the teeth broke easily," Barber explained, "then the limpet would not be able to feed and would die -- hence evolution selecting the strongest teeth over many years."
Strength is based on material composition as well as the shape of the structure. In addition to analyzing limpet teeth sets and individual teeth, Barber and colleagues Dun Lu and Nicola Pugno cut ultra-small samples out of the teeth. Even then, at miniscule sizes, the material proved to be incredibly resilient.
The limpet's teeth have been found to be the strongest biological structures on the planet.Asa Barber
Further analysis by the team found that limpet teeth are composites (meaning they consist of two or more constituent materials with significantly different physical or chemical properties) made from mineral fibers known as goethite. The fibers are bound together in a "glue" of chitin, a natural polymer.
"The strength of the tooth is due to the diameters of the fibers being below a particular size, which is about 60 nanometers, or over a thousand times thinner than a human hair,” Barber said.
Limpets have rows of teeth on a tongue-like appendage called a radula, Barber said. The limpet sits on a rock and rolls out its radula over the rock's surface.
"The teeth are under the radula to scrape over the rock surface," Barber said. "Algae on the rock surface is scraped toward the mouth of the limpet and this is how it feeds."
Barber estimates that there are a hundred rows of teeth on the radula. But even these super-strong choppers can become damaged from time to time, so there are always replacement teeth available from the many rows underneath the radula.
Barber and his team note that engineers use composite materials to make many things, including aircraft parts, hulls of boats, and Formula 1 cars.
Scientists, therefore, are eagerly eying limpet teeth, in hopes of duplicating their structure to fabricate higher performance materials. Duplicating the limpet tooth's resistance to abrasion could, for example, be useful in designing mining or digging equipment.
Peter Fratzl, of the Department of Biomaterials at the Max Planck Institute of Colloids and Interfaces, agrees that the material comprising limpet teeth holds promise for creating new and improved engineering materials. He told Discovery News that the new study "is extremely interesting in at least two ways."
"First," Fratzl said, "it shows that an intricate microstructure makes limpet teeth incredibly strong for biogenic material, certainly stronger than silk or cellulose. Second, the experimental approach, using tiny tensile specimens just a few microns long, is really impressive."
And, of course, what about human teeth? Why are they so prone to cavities and other problems? It's due to what we eat, the researchers said.
"Human teeth haven't evolved for our current diet," Barber said. "Maybe [they’d be sturdier] if we kept to the Paleo diet from birth?"