Academic nonsense! (scientific info on thiamine/thiaminase)

[DrKate]

So, is the solution to the myths surrounding thiaminase-"filled" fish to feed the fish themselves a varied diet and increase the quality of their surroundings?

Well, that one study says that the amount of thiaminase in alewives is unrelated to the amount of thiamine they contain. That last study I posted, on the forage species in the Great Lakes, found that thiaminase levels in some fish go UP with the amount of thiamine they contain (I didn't post that part). So I don't think that changing the husbandry and feeding of feeder fish is a 100% solution - they'd still contain thiaminase, but they may also contain more thiamine and might therefore be less deficient by the time they're digested. But you couldn't really know (unless you've got a thiamine/thiaminase test kit in your basement!) whether you had a safe feeder at the end of all that.

Could a parasite be the cause of these seizures, as opposed to the fish's thiaminase content?

Good point. Very generally, I know there are parasites that get into the brain, especially in non-adapted host species. But I don't know if there are any that could be transmitted from fish (or other feeders) to snakes. I'm not terribly hopeful that this has even been studied, but I'd love to know if anyone finds anything on it...

[Stefan-A]

(unless you've got a thiamine/thiaminase test kit in your basement!)

By the way, how is it actually tested?

[DrKate]

By the way, how is it actually tested?

Hee hee... Well, I just happened to see this when I looked up those other studies...

A Method for Measuring Total Thiaminase Activity in Fish Tissues
Zajicek, JL, et al.
Journal of Aquatic Animal Health vol. 17, no. 1, pp. 82-94. Mar 2005.
(Paraphrasing here, of course...)
1. Pulverize the fish you want to test and make an extract in buffer solution.
2. Add a known amount of radioactive thiamine and let stand 10 min.
3. Add ethyl acetate. Thiazole, one of the breakdown products of thiamine, is soluble in the organic solvent ethyl acetate while whole thiamine is not.
4. Measure the amount of radioactivity in the ethyl acetate. This tells you how much radioactive thiazole is there, from which you can calculate how much radioactive thiamine must have been broken down in 10 minutes, from which you can calculate how much thiaminase there must have been in your fish.

It seems that older assays were variants of this same general method (find a way to measure the amount of breakdown product created in a known time period). They just made some technical improvements that should give more accurate results.

EDIT: This is why if you look at any of these studies, they all talk about "thiaminase activity" - none of them is measuring the literal number of thiaminase enzyme molecules in the fish. What matters practically speaking is how much thiamine gets broken down between the time the fish dies and the time it gets to the predator's intestine, not how many enzyme molecules it takes to do that.

[aSnakeLovinBabe]

This is all very interesting!!! At least I can understand it but I am not sure everyone will.... I am still going to stick with the safest plan of action and avoid thiaminase altogether.

[Stefan-A]

Hee hee... Well, I just happened to see this when I looked up those other studies...

A Method for Measuring Total Thiaminase Activity in Fish Tissues
Zajicek, JL, et al.
Journal of Aquatic Animal Health vol. 17, no. 1, pp. 82-94. Mar 2005.
(Paraphrasing here, of course...)
1. Pulverize the fish you want to test and make an extract in buffer solution.
2. Add a known amount of radioactive thiamine and let stand 10 min.
3. Add ethyl acetate. Thiazole, one of the breakdown products of thiamine, is soluble in the organic solvent ethyl acetate while whole thiamine is not.
4. Measure the amount of radioactivity in the ethyl acetate. This tells you how much radioactive thiazole is there, from which you can calculate how much radioactive thiamine must have been broken down in 10 minutes, from which you can calculate how much thiaminase there must have been in your fish.

It seems that older assays were variants of this same general method (find a way to measure the amount of breakdown product created in a known time period). They just made some technical improvements that should give more accurate results.

EDIT: This is why if you look at any of these studies, they all talk about "thiaminase activity" - none of them is measuring the literal number of thiaminase enzyme molecules in the fish. What matters practically speaking is how much thiamine gets broken down between the time the fish dies and the time it gets to the predator's intestine, not how many enzyme molecules it takes to do that.

Thanks. I figured it would be done that way, but I wasn't sure.

[Zephyr]

Very generally, I know there are parasites that get into the brain, especially in non-adapted host species.

Generally the "rosy-reds" sold are albinos; I know it's not a major difference like two different species, however I'm sure there are some things that their genetics make them more susceptible to than their dark-pigmented brethren.
Goldfish definitely aren't native fish, so I'd assume that they'd have the highest likelihood of carrying pathogens.
Coincidentally... I don't think too many wild garters are consuming platies or guppies. Definitely mosquitofish, but not other species of livebearers.

[DrKate]

Coincidentally... I don't think too many wild garters are consuming platies or guppies. Definitely mosquitofish, but not other species of livebearers.

Sorry, I wasn't trying to suggest that they do - I did say "prey," but I just meant food in general, including store-bought feeder fish for captive snakes. Sorry to be confusing! (I doubt many wild garters are eating the marine species of silversides that are sold frozen, either!)