CLOSE
Original image
iStock

Why Does Salt Kill Slugs?

Original image
iStock

Salt and pepper go together, but salt and slugs don’t pair so well. If you’ve ever battled the slimy gastropods in your garden (or just had a sadistic bent as a kid), you know that a few pinches of salt can kill them. But why? What is it about salt that causes the creepy crawlies to wither?

The answer, in a word, is osmosis: the process that occurs when a solution meets a permeable membrane. A solution is a homogenous mixture of two (or more) substances where one substance, the solute, is dissolved in the other, the solvent. When you have a solution on both sides of a permeable membrane, the solvent tends to pass through the membrane to whichever side has more solute so that concentration on both sides is evened out. That’s osmosis.

A slug has quite a bit of water inside of it, and the cells that make up its skin have highly permeable membranes. When you sprinkle salt on a slug, it mixes with the water in the mucus that the slug secretes to help it move around, creating a salt-water solution. That solution has a higher salt concentration than the inside of the slug, so osmosis occurs and water from the slug’s skin cells passes through the membranes to dilute the solution and even things out. If you use enough salt, the slug will lose so much water that it dehydrates, dies, and winds up looking pretty shriveled.

Humans can handle salt without the same thing happening because our skin isn’t as permeable as a slug’s. Put some salt in your eye, though, and you’ll get a small sense of what the slug is going through.

Original image
Focus Features
arrow
Animals
25 Shelter Dogs Who Made It Big
Original image
Focus Features

If you’ve been thinking of adding a four-legged friend to your brood and are deciding whether a shelter dog is right for you, consider this: Some of history’s most amazing pooches—from four-legged movie stars to heroic rescue dogs—were found in animal shelters. In honor of Adopt-a-Shelter-Dog Month, here are 25 shelter dogs who made it big.

Original image
iStock
arrow
technology
This High-Tech Material Can Change Shape Like an Octopus
Original image
iStock

Octopuses can do some pretty amazing things with their skin, like “see” light, resist the pull of their own sticky suction cups, and blend in seamlessly with their surroundings. That last part now has the U.S. Army interested, as Co.Design reports. The military branch’s research office has funded the development a new type of morphing material that works like an octopus’s dynamic skin.

The skin of an octopus is covered in small, muscular bumps called papillae that allow them to change textures in a fraction of a second. Using this mechanism, octopuses can mimic coral, rocks, and even other animals. The new government-funded research—conducted by scientists at Cornell University—produced a device that works using a similar principle.

“Technologies that use stretchable materials are increasingly important, yet we are unable to control how they stretch with much more sophistication than inflating balloons,” the scientists write in their study, recently published in the journal Science. “Nature, however, demonstrates remarkable control of stretchable surfaces.”

The membrane of the stretchy, silicone material lays flat most of the time, but when it’s inflated with air, it can morph to form almost any 3D shape. So far, the technology has been used to imitate rocks and plants.

You can see the synthetic skin transform from a two-dimensional pad to 3D models of objects in the video below:

It’s easy to see how this feature could be used in military gear. A soldier’s suit made from material like this could theoretically provide custom camouflage for any environment in an instant. Like a lot of military technology, it could also be useful in civilian life down the road. Co.Design writer Jesus Diaz brings up examples like buttons that appear on a car's dashboard only when you need them, or a mixing bowl that rises from the surface of the kitchen counter while you're cooking.

Even if we can mimic the camouflage capabilities of cephalopods, though, other impressive superpowers, like controlling thousands of powerful suction cups or squeezing through spaces the size of a cherry tomato, are still the sole domain of the octopus. For now.

[h/t Co.Design]

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios