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Mokele

Poisonous (not venomous) snakes

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Quite often in non-technical sources, you find people talking about 'poisonous snakes', often referring to species such as cobras or rattlesnakes. And the usual smart-aleck response is "There's no such thing as a poisonous snake, only venomous snakes", the difference being that venom is a method of procuring prey (as in cobras and such) or fighting off predators (wasp venom), while poison usually refers to a chemical that must be consumed to have an effect.

 

Paper on poisonous garter snakes

 

In the pacific northwest, there's a small, harmless snake (the garter snake) with a wide ranging diet. One particular population preys mostly upon newts, the catch being that these newts contain tetrodotoxin (apparently aquired from bacteria; the same chemical is the toxin in pufferfish). As a result of their prey's super-potent nerve toxin, the snakes have evolutionarily modified the sodium channels in their nerves to be less responsive to that toxin (which has had secondary effects of decreasing nerve performance). Of course, this set up an evolutionary arms race, with more toxic newts evolving, which lead to more resistant snakes, which lead to more toxic newts, etc.

 

However, tetrodoxin takes a while to break down. The paper above shows that it disappears fairly fast from most of the snake's tissues, except for their livers, which it accumulates in large quantities for long periods of time. This has the potential effect of making these snakes toxic to many of their native predators, especially birds. Other species do this too (dart frogs actually get their poison from ants and beetles), so it's technically truly a poisonous snake.

 

So yeah, there you have it, a poisonous snake.

 

Mokele

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That`s Nice dear :)

 

although it doesn`t leave alot of opening for discussion, I DO have one question though, you mention tetrodotoxin as found in Fugu, and that the response is greater sodium chans etc... then you say "(which has had secondary effects of decreasing nerve performance)"

 

how does it affect them? and is that why they are so easy to catch?

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I have to do more research, but I would assume (and I'll check) the "voltage" gated Na Channel of the that particular snake would have a DECREASED AFFINITY for the toxin easily explained by different amino-acids in the extra cellular "toxin" binding site.

 

This is the case for the Fugu fish. There is a single point mutation in their voltage gated Na channel that renders TTX ineffective, so it does not explain their ease in catching :)

 

As far as curare goes, Anesthesiology use a forms of this of compound (i.e. aminosteroid based derivatives) for neuromuscular block and intubation during operations. They have to be careful which forms they use since as moleke mentioned it can be sequestered/toxic to the liver, which can be compromising to hepatically impaired patients. But the curare works though a "ligand" gated na channal that is opened by aceytcholine binding.

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I`m familiar with Tubocurarine, I`m guessing that Curare is an extract of that perhaps?

 

Tubocurarine`s just a muscle relaxant in effect, and as you said it affects acytlcholine, often given with a dissociative (such as ketamine) and the anaesthetic combined.

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Puffer fish are easy to catch because they are so slow. They don't have a particularly sleek body. There's an interesting correlation between genome size and how 'weird' fish look. The fish with with smaller genomes tend to be more weird looking, probably because they've lost genes for normal fishy development.

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I`m familiar with Tubocurarine' date=' I`m guessing that Curare is an extract of that perhaps?

 

Tubocurarine`s just a muscle relaxant in effect, and as you said it affects acytlcholine, often given with a dissociative (such as ketamine) and the anaesthetic combined.[/quote']

 

thats correct! though I they're using chemically modified forms of the stuff to day. Though the use of morphine as a dissociative is standard practice these days.

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I DO have one question though, you mention tetrodotoxin as found in Fugu, and that the response is greater sodium chans etc... then you say "(which has had secondary effects of decreasing nerve performance)"

 

Ahh, my bad, I meant that the snakes which have evolved resistance to this toxin seem to have lower nerve performance, and lower locomotor speed.

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