Salt Those Slugs

Comments

We have skin to protect ourselves from the molecules in salt.Slugs do not.

The reason that they foam is a process called osmosis. Osmosis is a
fundamental process that is involved in many branches of biology as well
as chemistry. The term osmosis describes a type of diffusion (diffusion is
when a chemical moves from an area of high concentration to a low
concentration, such as adding dye to water, it spreads out) involving the
net movement of solvent (the liquid part) molecules, as opposed to solute
(the things dissolved in the liquid) molecules, across a semi-permeable
(that lets something's but not others through) membrane from an area of
high water/low solute concentration to an area of low water/high solute
concentration (hypotonic). In this case the semi-permeable part lets water
across the membrane but not the dissolved chemicals. All organisms are in
state of osmotic balanced; you are at the moment. The reason you get
thirsty is that you lack water and your cells are depleted of it and
shrivel up. So how come you don't foam if you put salt on your skin. Well
you skin is unlike a slug. One of the critical steps in evolution was the
development of our skin, which is flexible, hard wearing and prevents
water from escaping. But slugs didn't evolve this far. Their skin does not
prevent water from passing across it; it acts as a semi-permeable
membrane. So if you add salt to a slug you change the osmotic balance
across the membrane. Now the slug has lots of salt (solute) on the outside
in the water. So effectively that water is less concentrated (it has other
things in it) relative to the water inside the cell. So the water inside
the cell rushes out across the membrane to make things equal. This makes
it look like the slug is foaming.

Please do not kill slugs using salt. This is a terrible way to die! The thick goo you see on the slug after salt is put on the body is actually the fluid or blood of a slug that rushes to the skin's surface to dilute the salt. Dehydration is a nasty way to go. Simply remove the Banana Slug from your garden and place it back in a nearby forest where it can continue its important role as a forest floor decomposer.