Oh well, I've nothing much to blog tonight so I'm thinking of posting this interesting fact.

[Just not long ago, Kim Heng was asking "What is the exact reason that snails and slugs die when salt is applied?" Suprisingly, when I searched online, I found out that one of students from The Evergreen State College asked the same question too and this is a reply from Andrew D. Brabban, Faculty, Biology. I hoped it answered Kim heng's doubts and it already answered my doubts. =D

What is the exact reason that snails and slugs die when salt is applied?

Message: What is the exact reason that snails and slugs die when salt is applied?
Such as what chemical reactions take place.

Reply:

You are right in that this is a sort of a chemical reaction, but not
really, in that no actual physical change is occurring to the chemicals.
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
your 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.

( Reply from Andrew D. Brabban, Faculty, Biology, The Evergreen State College )
Special thanks to him.


Joyful,
Don