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Ingenious web construction and energy stored in stretched silk strands lend spiders super powers to lift animals too heavy for the spiders' tiny muscles to support.
Transcript
00:00You've probably seen spiders catch insects that are smaller than they are in
00:04their sticky webs. But did you know that there are some spiders that can catch
00:08prey that's much larger than they are? And they do it by wrapping them in sticky
00:13strands of web and lifting them off the ground.
00:20Now scientists have known about this behavior for some time, but it hasn't
00:25been very well studied. So for the first time a group of scientists took several
00:30of these spiders and observed them doing this prey lifting behavior under
00:35laboratory conditions. The spider built this web. In the connection between the
00:39main frame of the web, which is the part dense of threads, and the surface below,
00:46the spider spin these threads. And these threads are actually the feature that send
00:54signals to the spider that something is hitting, something is passing below.
01:00So the elastic energy stored in the frame, which is basically we have to think about
01:06an elastic, you know, so if you pretension an elastic, it will recall with an elastic
01:11force. If the prey is small, so just one thread is necessary to lift it.
01:16Unfortunately, when the prey is big, of course the one thread is not necessary,
01:23but this is what actually poses a challenge to the spiders. The logic is exactly the same as before.
01:29So the spider produce thread as elastic and it pretensions them. Then it attaches this thread to
01:38the prey. And this is pretty cool because it's one of the few cases where the spider is actively
01:45involved in the hunting by means of the web. It's no more a trap, a passive trap in the sense that
01:51the web works perfectly as it is, but the spider is getting involved too. Because normally the
01:58spiders are just sitting and waiting for the prey that enters the web. And that's it.
02:04As you can see, the structure of this web is particularly complicated. There are different
02:09types of silk. So each part of the web has its own silk for that specific function.
02:17And these are the supporting threads. And as you can see, there are two types of threads,
02:22two threads in these supporting threads. One thread is produced by a gland. The other one
02:28is produced by another gland. The very same thread, but this thread is coated with these droplets
02:37that are produced by another type of silk. And we have three types of silk. Where the spider joins
02:43together these threads, it uses this kind of cement-like silk, which is another type of silk. So four
02:52different types of silk are used to produce this frame. It also wraps the prey because it has also
02:58to mobilise locally the prey in order to avoid the prey to move too much. And it uses another type of silk
03:06to wrap it. Normally, material scientists go crazy with this because the spider is a perfect factory of
03:12silk. It produces multifunctional materials in less than milliseconds. Each one optimise for that property.
03:21So it's crazy. They are like machines. They are super efficient. And there are like 49,000 different species of
03:32spider. Each one produces different type of silk with different properties up to the species, up to the individual.
03:39So basically, we do not know nothing about silk. When you start studying in-depth things, you realise
03:45that you don't know anything about them. And I don't know, we use two species of spider, but there are
03:50other species of spiders, as I said before, that must be investigated from this point of view. There are
03:55also other type of prey that may behave differently. So this was just the first insights in this direction. But there are
04:03tons of possible questions that can be answered. So even though scientists now have a better idea
04:12as to how the spiders are able to trap large prey and actually lift it up off the ground, there are
04:18still a lot of unanswered questions about how exactly the spiders make all these different types of silk,
04:25and what are the limits of how they can use them.

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