Venom Potency and the Evolutionary Time Scale

[The Snark]

(Apologies extended beforehand. The day started at 04:00 with the toilet filled with yellow slime molds and mud, digressed into me trying to explain the rudiments of a basic water system to a bunch of cro-magnon morons and ended at 22:00 with a lecture on this thread topic. IE I fell asleep in class. Therefore my fuzziness on this.)

Theory: 'The longer an animal resides in a fixed, limited locale, the more potent the venom it develops. The more transient, the more adaptive the venoms and consequently the less refined.'

Simplified, if an animal has developed an extremely potent venom, somewhere in it's evolutionary time scale it resided in a fixed locale for an extended period of time. This need not apply to the present time but somewhere in the animals past.

The fixed locale does not need to be an actual location. It can be an environmental area and this area itself could have moved and/or presently be moving.
In the event of an animal that possesses a virulent venom in a location where it is obviously a transient, it has been displaced. This can be used to trace back the animals history and in the process the biology of the probable locations the animal lived in where it had 'set up shop' for the required period of time.

Aaaaaannnd, that's where I faded out and woke up to the room emptying out.

In my mind I've been toying with Atrax venom and a big thanks to Aus being more or less frozen in time for eons, and their Taipans which have genetically been established to have parked in their present locales for at least 10 million years.
The same would apply with the virulent venom versions of Phoneutria in very certain specific locations while other Phoneutria living nearby were transients, adaptive and possess less powerful venoms.
The Sicarius would also fit right in, parked in sand dunes and sandy areas and more or less moving about with the environment that created and maintained them - evolition at the speed of geological shifts.
And again with Latrodectus. Multiple virulent venoms speaking of an incredibly ancient time line.


Anyone have any thoughts on this? Theories?

 

[schmiggle]

Well according to this, black widow spider venom evolved rather quickly:
https://www.sciencedaily.com/releases/2015/01/150106081622.htm
Isn't venom potency usually linked to how quickly an animal needs to kill prey and how much it can inject at one time? Vipers, for example, often have less potent venom than elapids as well as smaller venom glands, because they can inject the venom deeper where it is more likely to reach something important. Sicarius needs to kill quickly so its prey doesn't get lost, and in Atrax, only the males are severely toxic, and only because they have robustotoxin in their venom, which is particularly toxic to primates but not other mammals. The only primates in Australia are humans, which haven't been there all that long, and robustotoxin is probably not for a specific prey group, because then males and females would both have it (although it's admittedly possible that they have different primary prey groups). My guess is that sydney funnel web males only became particularly toxic recently, perhaps because human settlement meant that they had some new kind of pressure to deal with directly related to people.

 

[The Snark]

I'm wondering what these different eggheads consider long and short periods of time.

 

[checkmate]

My biology is rusty (uni curriculum only required to take 1 semester) and but I'll take a stab.
Say species X has a particular venom potency. Mutations have caused a low venom potency in some individuals of X and high potency in other individuals. Say their primary food source requires a minimum amount of venom, Y, to become incapacitated. Individuals of X with venom potency <Y die out. Over time, the average venom potency increases in the species. With regards to locale, species that are able to migrate over relatively large distances face less competition for food and have an increase in prey options. Prey also encounter mutations to resist the venom. Individuals with low natural resistance die out and the average resistance increases in that species causing the minimum venom potency Y to increase. That's my hypothesis.

 

[The Snark]

Excuse me but I'm still stuck in the time frames thing. Having a temporal hiatus. We have different species of Latro the planet over. So we had a time frame involved where they evolved. Then we have the same basic venoms, but the LD50's are all different so the venom must have evolved with the species possibly relative to the locale. Just what in heck is the time frame we are looking at?

 

[The Snark]

Excuse me again. In that link @schmiggle gave us. Is the relatively rapid development referring to the latrotoxin in general or the variations as found in the different species?
I wish that these biologists would take a page from the geologists or astrophysicists book about nailing down what exactly they mean by rapid or slow.

 

[checkmate]

According to this theory, toxin-producing genes in young venomous groups that enter a novel ecological niche, experience a strong influence of positive selection that diversifies their toxins, thus increasing their chances to efficiently paralyze relevant prey and predatory species in the new environment.

However, in the case of the ancient venomous groups, where the venom is already "optimized" and highly suitable for the ecological niche, the venom's rate of accumulating variations slows down under the influence of purifying selection, which preserves the potent toxins generated previously.

https://phys.org/news/2015-11-two-speed-evolution-animal-venom.html

http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1005596

 

[RTTB]

I've found reading this to be a very interesting topic. I can't really intelligently comment theory wise. Perhaps it's evolved perfected venom for efficiently quickly disabling prey in the specific isolated niche they have dwelled in for eons. But one could say that for all venomous invertebrates.

 

[schmiggle]

That paper is very interesting, although it seems to me they may be jumping the gun a bit (just a gut feeling whose source in the paper I can't seem to place).

 

[The Snark]

"However, species that have entered the stage of purification and fixation may re-enter the period of expansion if they experience a major shift in ecology and/or environment."
Read more at: https://phys.org/news/2015-11-two-speed-evolution-animal-venom.html#jCp

I think this aptly proves why I fell asleep at that lecture. Well, more to the point, I think I have a built in sanity protection mechanism that kicks in when juggling more than 20 or so variables in my mind at once.