Buzz
Salt and pepper make a classic combination, but salt and slugs are a different story. Anyone who’s tried to deal with these slippery creatures in the garden (or perhaps enjoyed some childhood mischief) knows that just a pinch of salt can be lethal. But why is that? What’s so harmful about salt to these little crawlers?
The answer is simple: osmosis. Osmosis is the process that happens when a solution meets a semi-permeable membrane. A solution is a uniform blend of two or more substances, where one substance (the solute) dissolves in another (the solvent). When a solution is on both sides of a permeable membrane, the solvent moves across to the side with more solute, balancing the concentration. That’s osmosis in action.
Slugs contain a large amount of water, and the skin cells that make up their outer layer have highly permeable membranes. When salt is sprinkled on a slug, it mixes with the mucus secreted by the slug, forming a salt-water solution. This solution has a higher salt concentration than the slug’s insides, so osmosis kicks in, causing water from the slug’s cells to flow out in an attempt to balance the concentrations. If too much salt is used, the slug loses enough water to become dehydrated, shriveled, and eventually dies.
Humans don’t experience the same effects from salt because our skin isn’t as permeable as a slug’s. However, if you were to get salt in your eye, you’d get a tiny taste of what the slug experiences.
