What Exactly does copper do to snails/inverts?

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What Exactly does copper do to snails/inverts?

Postby Steph on Fri Jun 25, 2010 5:20 pm

Ever since I learned that copper was lethal to snails / inverts, I've been curious to find out exactly how / why. I've googled it a number of times with different wording etc. but all I get is page after page of non-info, i.e. yes it is lethal, but never an explanation as to why.

I recently learned that the blood in (some) snails and (some) inverts is copper based. I knew it was a hemocynanin-based blood but I just learned that hemocyanin was a copper-based chemical/molecule. So where we have red iron-based (haemoglobin) blood, many snails and other inverts have a copper-based blood, which tends to look clear (it can appear light/pale blue when saturated with oxygen.)

Does this mean that copper in solution in the water affects their circulatory system? Or their celluar respiration? Maybe interfering with their blood's ability to bond with oxygen?

I'm just curious, one of those people who isn't satisfied to know a fact until I know the whys and wherefores behind the fact.

And incidentally, while our beloved Apple Snails' blood is hemocyanin / copper based, that of some other snails / pests such as the planorbidae is not. Planorbids' blood is iron-based, which contributes to their colouring. So if the lethality of copper to inverts is in fact related to hemocyanin, then it would be at least less-lethal to those inverts with red blood cells rather than the usual clear. (This is speculation of course since I don't know why it's lethal in the first place...)

Anyhow - just very curious and unable to find any scientific info that explains this.

Cheers!
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Re: What Exactly does copper do to snails/inverts?

Postby khayes on Fri Jun 25, 2010 9:08 pm

Hi Steph,
Well, copper toxicity is achieved through a number of pathways in molluscs and other invertebrates. First you are correct, that molluscs and other inverts that use haemocyanin as the circulating oxygen carrier require a certain level of copper in the environment and in their systems at all times. However, when those levels are exceeded it may become toxic, and this level is different for various invertebrates, and even different species within a group of invertebrates (i.e. molluscs). For example, acute toxicity ranges in molluscs is 40 to 9000 g/L. Even those molluscs that don't use hemocyanin suffer from copper toxicity, for example Biomphalaria uses hemoglobin, but still suffers from the effects of copper toxicity.

As I mentioned, there are several ways in which copper can adversely impact the metabolism of invertebrates. It can bind to macromolecules (proteins, lipids, etc) and alter their functions directly. It may also displace other metals, such as zinc, in some enzymes altering their functionality. The most direct route of action by copper is through the production of highly toxic hydroxyl radicals from intracellularly generated hydrogen peroxide. These radicals cause damage to the cell membranes through the process of lipid peroxidation, and denature enzymes through protein oxidation.

As you can imagine all of these modes of action play havoc with the normally metabolic processes that snails need to carry out in order to survive. Primary among these for freshwater and marine snails is the ability to osmoregulate.

The details of how this all happens is quite complicated and I have simplified the basic issues here. If you'd like more details let me know and I can send you some reading material.

Cheers,
Ken
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Re: What Exactly does copper do to snails/inverts?

Postby Steph on Sat Jun 26, 2010 1:49 pm

Hi Ken,

Thanks very much, that's the sort of information I've been looking for. I'd probably get befuddled by anything more technical but your explanation is great.

Cheers!
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