How do you get the venom from a spider?
We may be safe from deadly spiders here in the UK but that’s certainly not the case in Australia, home to the funnel-web spiders, the most venomous spiders in the world. But it turns out that the same venomous chemicals that can kill us if we get bitten are being developed into life saving drugs. Sally Le Page spoke with Samantha Nixon from the University of Queensland to find out more about venom...
Samantha - It's made of thousands of different molecules. And what's really cool about the spider venom peptides is that they are really, really stable so they can survive heat, they can survive acid. And so these very complex, very stable toxins really give spiders the evolutionary edge to become the most successful terrestrial predators on the planet.
Sally - So we just heard about the cellar spider having particularly nasty venom. What kind of spiders do you work on and how does their venom compare?
Samantha - I'm really interested in tarantulas. And the other spiders that I really focus on in my job are the world's deadliest spiders, the Australian funnel webs. It does this incredibly impressive threat display where it rears up on its back legs, flexing its fangs, and it even drips venom off the tips of its fangs.
Sally - Oh wow. It's not messing around. It's like "I have venom and I'm prepared to use it".
Samantha - It is really telling you like back off, this is not a fight that you want to get into.
Sally - But if it's deadly... a small spider, I mean small compared to a human, it's not going to be eating a human for breakfast. So why does it need such powerful venom?
Samantha - That is such an interesting question. And it turns out to be a really interesting quirk of evolution. They spend most of their lives underground in a burrow where they're quite safe, except that the males have to leave their burrows to go out and find female funnel web spiders. And so while they're out looking for the ladies they're exposed and it turns out that the males have evolved to produce very high amounts of what we call delta hexatoxin or delta atracotoxin. And this is the lethal toxin within the funnel web spiders. And it prevents our nervous system from turning off. So your muscles are constantly spasming and your lungs are trying to breathe, but they end up going into paralysis because there's nervous system overload. This toxin probably evolved just to cause pain, but just because of very slight differences in a human nervous system, it ends up overloading our system so that we can't breathe anymore. And cats and dogs are actually mostly okay when they get bitten by funnel webs because their nervous system is just very slightly different.
Sally - This all sounds horrendous. If I lived in Australia, I would try and stay as far away from funnel-web spiders as possible. But you have them in your lab, am I right to say?
Samantha - Yes. And I totally understand that because I actually was arachnophobic. And I decided to join the research lab to force myself to get over my fear. I manage around about a hundred spiders as well as scorpions and other sort of venomous animals. And I named them all, which helped me to get over my fear. Can't be scared of Beyoncé the tarantula, or...
Sally - Is Beyoncé your favourite?
Samantha - Beyoncé is definitely one of my favourites.
Sally - What is it you're looking at when you're researching this venom?
Samantha - So our lab is broadly interested in how venoms have evolved, what they're made out of and how we can use them to make new medicines and new technologies. So because spider venoms mostly target the nervous system, we do a lot of research into using spider venoms to make new medicines for neurological disorders: things like stroke, chronic pain, epilepsy... Actually by studying a funnel web spider found in Queensland, Australia, my home state, we were able to find one toxin, which actually protects the brain after a stroke and is able to help protect the heart after a heart attack. That toxin is called HI1A. It doesn't stop you from having a stroke or a heart attack, but it helps to slow down all of the death from the lack of oxygen. So we were able to rescue as much as 70% of the stroke size when we administered this peptide in rats, even eight hours after giving them a stroke.
Sally - When you are studying these venoms to work out how you can extract useful chemicals from them, presumably you have to have a vial of venom to look at. So how on earth do you get the venom out of a spider?
Samantha - Very carefully is the short answer. So we call the process milking, and there's a couple of different ways that we go about it. So for the tarantulas, it's a little bit like how you would milk venom from a snake.
Sally - Because we all know how to milk venom from a snake. That's something we all do on a regular basis. I was just milking a snake for its venom last weekend.
Samantha - You know, just normal Friday night kind of activities. I anaesthetise the spider with a little bit of carbon dioxide gas, just makes the spider a little bit sleepier, and I basically will pick the spider up. And then I position the spider over a little sort of test tube with a little bit of plastic over the top. And I, while the spider is still kind of asleep, hold the fangs away from their body and get them to bite down through the plastic. Now, as I said, the spiders don't want to give up their venom if they don't have to. So I give them a very small electric shock to the muscles over their fangs. It doesn't hurt the spider. It's just enough for the muscles to squeeze down and push the venom through the fang into the tube.
Sally - So that's the tarantulas, which I imagine are the easier ones. So what about the huntsman and the funnel webs?
Samantha - The huntsman, I would have to say are the trickiest ones, actually. I have to set up two tiny little pipette tips and then try to put each fang into a pipette tip.
Sally - No stop it, you're making this up.
Samantha - I wish I was making it up, but I have to try to do it quickly because the huntsmans are fast and strong and they do not enjoy this process at all.