Scorpion's two types of Venom

[fusion121]

Also, as I noted in the earlier thread, there have been no studies to even show that venom production imposes a significant metabolic cost on scorpions

I'm surprised this hasn't been investigated considering the number of studies of scorpion venom, it would be interesting to find out as the author does seem to have taken it a priori. The leakage of the venoms more mobile components would seem to the better explanation for prevenom especially considering the HPLC results.

 

[Eurypterid]

I'm surprised this hasn't been investigated considering the number of studies of scorpion venom, it would be interesting to find out as the author does seem to have taken it a priori. The leakage of the venoms more mobile components would seem to the better explanation for prevenom especially considering the HPLC results.

In the literature this is a common assumption due to the protein content. But as far as I know it has never been tested, and the authors cite no source in this paper, so they apparently don't know of such an experiment either. So, while venom may be a costly substance to make in an absolute sense, it may not be a significant cost when put in terms of actual usage.

I've been thinking of having a student do such an experiment, but there are some diffculties. We could extract venom and measure the metabolic costs of replacement, but we run into some difficulties putting that into the context of real-world venom usage. It would be difficult to quantify the average amount of venom used by a scorpion over a given period of time. It would be hard enough to get a good sampling of the average number of stings the scopion may have to deliver over say a week, and that is further complicated by not being able to measure the amount of venom used in each sting. Without that data there is no way to determine whether there is actually a significant metabolic cost associated with venom usage in nature. Hmmm. Just writing this I thought of an experiment that could probably give us the information we need, though it wouldn't be easy. Maybe I'll have a couple of students work on it this fall.

 

[fusion121]

In the literature this is a common assumption due to the protein content. But as far as I know it has never been tested, and the authors cite no source in this paper, so they apparently don't know of such an experiment either. So, while venom may be a costly substance to make in an absolute sense, it may not be a significant cost when put in terms of actual usage.

I've been thinking of having a student do such an experiment, but there are some diffculties. We could extract venom and measure the metabolic costs of replacement, but we run into some difficulties putting that into the context of real-world venom usage. It would be difficult to quantify the average amount of venom used by a scorpion over a given period of time. It would be hard enough to get a good sampling of the average number of stings the scopion may have to deliver over say a week, and that is further complicated by not being able to measure the amount of venom used in each sting. Without that data there is no way to determine whether there is actually a significant metabolic cost associated with venom usage in nature. Hmmm. Just writing this I thought of an experiment that could probably give us the information we need, though it wouldn't be easy. Maybe I'll have a couple of students work on it this fall.

It would be important research I've read papers on venom metering by venemous snakes and in those to they were unable to refer to any empircal data on the metabolic cost of venom production. I've no knowledge of how one sets up experiments like this. I assume its not as simple as taking scorpions of known mass, not feeding them, and then milking each one for different amounts of venom and then correlating decrease in mass (and hence I assume expended energy, obviously ignoring the mass of the milked venom itself) with mass of venom used? Though that would have been my first guess.

 

[Eurypterid]

Simply using masses wouldn't be very accurate, since the mass of expended venom would be so small compared to the total mass of the animal. Changes would be complicated by defication, dehydration, etc. Just too messy. But the caloric content of venom could be measured, average and total metabolism of scorps could be measured, venom production rates could be calculated, etc. These experiments could give us a good idea of the base venom-producing capacity of scorpions, and then we would just need to measure average usage in nature. I say "just", but this would actually be the harder part. I guess I just found a use for my 500+ C. gracilis.

 

[fusion121]

Simply using masses wouldn't be very accurate, since the mass of expended venom would be so small compared to the total mass of the animal. Changes would be complicated by defication, dehydration, etc. Just too messy. But the caloric content of venom could be measured, average and total metabolism of scorps could be measured, venom production rates could be calculated, etc. These experiments could give us a good idea of the base venom-producing capacity of scorpions, and then we would just need to measure average usage in nature. I say "just", but this would actually be the harder part. I guess I just found a use for my 500+ C. gracilis.

I'll be very interested to read the results if you publish a paper on it, as I suspect will many researchers with venemous animals would be.

 

[Eurypterid]

I'll be very interested to read the results if you publish a paper on it, as I suspect will many researchers with venemous animals would be.

Well, with student research it may take a year or so, but if we get interesting results I'll certainly post something here.