Gastropods and Salt

[Theophrastus]

An interesting question on hand, for those at SFN (proclamation)!

I'ts always been stereotyped in various television shows (particularly pointless children's shows, which I have sadly been coerced to watch due to the existence of younger siblings), that gastropods (regardless of genus; sometimes sea slugs, sometimes terrestrial pulmonates) seem to almost bubble and froth, in an almost disintegrative manner, when on contact with salt. Why does this seem to occur, or does it even? After all, there are tons of saltwater gastropods? I know magnesium chloride, in particular works as an anesthetic, in reasonable quantities, however, what does our dear friend common table salt have to do with it? Any help?

 

ps: It seems that salt has a dark side as well!

 

"(to be stated in a darth vaderly voice) Join the dark side!...we have cookies!":-)

[iNow]

It's all about osmosis. The slugs are mostly mucous, and the water from inside is drawn outside the slug, and taken up by the salt. In salt water, the moist environment helps avoid the problems which come with lost moisture.

 

 

http://www.newton.dep.anl.gov/askasci/gen06/gen06261.htm

Slugs use slime for many things like moving, breathing and reproduction. I won't go into a long detailed explanation of why slugs need slime, but the link below is very good if you are interested. When you pour salt onto a slug, the slug appears to melt. What is actually happening is the liquids and "blood" inside of the slug are sent to dilute the salt and maintain the mucus layer. Too much salt will effectively dehydrate the slug's body and kill it by making all of the liquid inside go to the outside. Think about this if it could happen to you!

 

<...>

 

This is due to osmosis. The skin of the slug acts as a semi-permeable membrane where there are different concentrations of salt and water on each side. Remember that water will move from an area where there is more water to an area where there is less water. The salt that you sprinkle on the slug mixes with water in the slime on the outside of the slug to make a salty solution. In any solution there is only so much room, so if there is a lot of salt, there is not a lot of water. There is more water, less salt on the inside of the slug, so water leaves the slug to mix with the salt outside the slug in order to equalize (or "more equalize") the water on both sides of the membrane. There is a net loss of water from the slug and it dehydrates to death.

[Theophrastus]

Ah, of course, now I understand. It's similar to the fashion cells regulate concentrations and the like. I was thinking it might have been something chemical, but it seems I've been proven wrong. Thanks iNow! :-)That question's been bugging me for quite a while.

 

ps: sorry for the excessive use of smiles...

Edited June 12, 2009 by Theophrastus
revision of content

[iNow]

No worries.

[Theophrastus]

Ah, a secondary question. Why does magnesium chloride, in particular, act as an anesthetic for gastropods? This, at least, must be a variation upon the initial idea, as while osmosis would be a pathway for water, for anesthetic purposes, the concentration of the solution, must be stringently controlled, and furthermore, only result in the ingestion of the necessary quantity of the salt. Why does it perform in such a manner? Surely, this must be more of a chemical action?

Edited June 17, 2009 by Theophrastus
addition of content

[iNow]

Unfortunately, that particular question is beyond my current knowledge. When I looked it up, most of the sites I read were for new age oils and crap, so the method of action wasn't readily apparent. Someone like YT2095 or one of our other resident chemists may know.

 

I looked at the wiki, and it mentioned that it helps with certain growth processes, so if I were to guess I'd say that it boosts clotting and immune-type response (although, I can't say if slugs have immune systems in the traditional sense).

 

Really interesting question, that.

[Mokele]

According to this textbook, "magnesium competes with calcium for synaptic transmission".

 

Also, iNow, if they mentioned clove oil, it's actually legit - clove oil can be used to induce sedation and analgesia in pretty much anything with a permeable skin and/or gills.