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Newly discovered spider builds spring loaded snare to catch ants

phys.org

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Re: Newly discovered spider builds spring loaded snare to catch ants

#51

Post by salynchnew »

ajuc wrote: post #3
matheusmoreira wrote: post #2

I wonder why biological organisms are capable of such absurdly high accelerations. Article reminded me of cnidocytes which apparently produce anywhere between 40,000 and 5,410,000 g. Is it because of the small masses involved?

Strength of fibers scales with crossection area, mass scales with volume.

There are probably some other interesting adaptations involved, like the fact that the surface of a mantis shrimp's (shell? carapace?) selectively filters out sound waves (and thus, shockwaves caused by its own "punch").

Re: Newly discovered spider builds spring loaded snare to catch ants

#53

Post by prewett »

Foskya wrote: post #4

It is truly fascinating, I wonder how it evolved like that. Before becoming a spring as it is today how was it hunting in the past? What constraints made it need such a mechanism instead of a typical web?

This sort of thing makes me think that if I were engineering a biome, this sort of specialized spider would be exactly how I would solve the problem of a species that I accidentally made too prolific. The spider is a targeted fix: only preys on the ants, and if the ant problem ever resolves itself, the spider goes away.

I think this is a case where the theory of evolution feels pretty handy-wavy and doesn't answer the mechanism of how this happens. The article even talks about "bioengineered" silk! There are certainly lots of cases of evolution, so it is clear that things do evolve, but the problems of a theory are revealed in the edge cases, and I think this spider suggests that the theory really needs a lot of work to be a robust theory. I don't think a simple gradient descent (evolving toward more fitness) has explanatory power in this case. A theory that hand-waved around edge cases like this would never fly in Physics; at best it would be considered a holding theory until a better one could be found, like dark matter.

(Plus, I think it's fun to think about bioengineering in a sci-fi, or even Babylon 5 way)

Re: Newly discovered spider builds spring loaded snare to catch ants

#54

Post by mc_maurer »

prewett wrote: post #53
Foskya wrote: post #4

It is truly fascinating, I wonder how it evolved like that. Before becoming a spring as it is today how was it hunting in the past? What constraints made it need such a mechanism instead of a typical web?

This sort of thing makes me think that if I were engineering a biome, this sort of specialized spider would be exactly how I would solve the problem of a species that I accidentally made too prolific. The spider is a targeted fix: only preys on the ants, and if the ant problem ever resolves itself, the spider goes away. I think this is a case where the theory of evolution feels pretty handy-wavy and doesn't answer th…

Couple things here:

First, ecosystems don't work on this concept of "balance" or "problems to fix". There are ecological niches that are exploited by a species or not. We have both generalists and specialists, predators that will eat anything and predators that have specialized in a particular prey or hunting approach. The world is full of organisms with remarkably complex behaviors, the field of evolutionary biology would collapse if this sort of behavior disproved it.

Second, there's really nothing hand-wavy about how specialized behaviors evolve, and in fact there is a mountain of research in the fields of evolutionary biology and behavioral ecology that have significant explanatory power here. I would argue that you're the one being hand-wavy saying "I don't think a simple gradient descent...". Evolution is not a simple gradient descent, and no evolutionary biologist would ever argue that it is.

Re: Newly discovered spider builds spring loaded snare to catch ants

#55

Post by mc_maurer »

enjrolas wrote: post #17

The part from the paper which is so interesting is why the ant bites the trap in the first place. The paper suggests that the spider puts out a pheromone that attracts the ant and triggers the ant to aggressively bite the snare, but the pheromone only does this for the spider's target species, the green tree ant . The researchers watched three other ant species check out the snare, go "meh", and move on, unharmed, wi…

Ultimately, it's probably due to the rate of encounter with this species and the evolution of the pheromone towards the most consistent and intense response from that particular species. It's likely that a more general pheromone wouldn't induce such a consistent response, since it would be a less specific and reliable cue from the ant's perspective. So if you encounter lots of different ant species, a more general pheromone with a 50% response rate could work, but if you primarily encounter this ant species, a more specific pheromone with a 90% response rate is going to confer a greater fitness advantage.

Could be due to the rate of encounter with this species vs. other species, could also be due to the consistency of response with more general vs. specific pheromones. You start with spiders with silk/pheromones that ants are a little more aggressive towards, then variance in that chemical makeup leads to fitness advantages. If the pheromone confers a strong advantage in a specific ant,

Re: Newly discovered spider builds spring loaded snare to catch ants

#56

Post by mc_maurer »

enjrolas wrote: post #40
abrookewood wrote: post #22

Earlier quoted context omitted.

Yeah, that is pretty crazy. I wonder what it smells like? Has to be an enemy specific to that ant species right?

that's a good question -- the paper describes it triggering aggression in the ant within milliseconds of it probing the snare with its antenna. I don't know the basis for it, but that's some down-to-the-metal ant programming right there

You should read up on manipulative parasites too! Things like wasp larvae developing inside an insect and changing its behavior through chemical manipulation of neural pathways. Some really remarkable specialization!

Re: Newly discovered spider builds spring loaded snare to catch ants

#57

Post by isomorphic_duck »

prewett wrote: post #53
Foskya wrote: post #4

It is truly fascinating, I wonder how it evolved like that. Before becoming a spring as it is today how was it hunting in the past? What constraints made it need such a mechanism instead of a typical web?

This sort of thing makes me think that if I were engineering a biome, this sort of specialized spider would be exactly how I would solve the problem of a species that I accidentally made too prolific. The spider is a targeted fix: only preys on the ants, and if the ant problem ever resolves itself, the spider goes away. I think this is a case where the theory of evolution feels pretty handy-wavy and doesn't answer th…

It might be more helpful to think of it as small changes in “genome-vector” taking place across generations of the species with the filter of it being not bad enough to cause extinction of the bespoke variation, as opposed to evolving towards more fitness as an optimisation objective. When thought of like this, one can imagine how high-dimensional the “feature”-space becomes, which leads to such intricate engineering we see in nature.

Re: Newly discovered spider builds spring loaded snare to catch ants

#58

Post by TooSmugToFail »

zacharyfmarion wrote: post #35
spidercat wrote: post #34

Earlier quoted context omitted.

Children of Time is one of the best books I've ever read, it's honestly amazing. It might be my all-time favorite. Seconding this recommendation!

Thirding it! This is your sign, go read it

Ok, this was my sign.

Re: Newly discovered spider builds spring loaded snare to catch ants

#59

Post by mc_maurer »

isomorphic_duck wrote: post #57
prewett wrote: post #53

Earlier quoted context omitted.

This sort of thing makes me think that if I were engineering a biome, this sort of specialized spider would be exactly how I would solve the problem of a species that I accidentally made too prolific. The spider is a targeted fix: only preys on the ants, and if the ant problem ever resolves itself, the spider goes away. I think this is a case where the theory of evolution feels pretty handy-wavy and doesn't answer th…

It might be more helpful to think of it as small changes in “genome-vector” taking place across generations of the species with the filter of it being not bad enough to cause extinction of the bespoke variation, as opposed to evolving towards more fitness as an optimisation objective. When thought of like this, one can imagine how high-dimensional the “feature”-space becomes, which leads to such intricate engineering…

There's also typically a ton of standing genetic variation that is relatively fitness-neutral, but can then lead to more rapid or directional evolution if conditions change. For example, standing variation in silk elasticity may have been more fitness neutral when capturing other prey, but after encountering this ant species, spiders with more elastic silk were more successful and had a fitness advantage.

Re: Newly discovered spider builds spring loaded snare to catch ants

#60

Post by xboxnolifes »

enjrolas wrote: post #17

The part from the paper which is so interesting is why the ant bites the trap in the first place. The paper suggests that the spider puts out a pheromone that attracts the ant and triggers the ant to aggressively bite the snare, but the pheromone only does this for the spider's target species, the green tree ant . The researchers watched three other ant species check out the snare, go "meh", and move on, unharmed, wi…

> but the pheromone only does this for the spider's target species

Isn't this concluded through observational studies? Is it possible that its just not universally true, like it still impacts, idk, 0.01% of this ant's species due to gene diversity?

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