Spider webs capture more than just prey. They are also full of animal DNA


As it happens6:05 a.m.Spider webs capture more than just prey. They are also full of animal DNA

Josh Newton probably isn’t very popular with Spiders. After all, Australian scientists tend to destroy their hard work.

“I liken it to when Princess Fiona Shrek makes cotton candy for Shrek out of cobwebs, where she gets a stick and simply wraps it around the cobweb for him. But I do it with a clean, sterile stick,” said Newton, a PhD student in life sciences at Curtin University. As It happens host Nil Köksal.

“And then I just wrap the spider web, put it in a little tube, and take it back to the lab.”

But he has a good reason. It turns out that spider webs trap more than just unwitting insects. The sticky surfaces also contain a wealth of genetic material from dozens of animal species living nearby, making them a powerful tool for measuring biodiversity.

In a new study, Newtown and colleagues identified DNA from 93 different invertebrates on spider webs in Perth, Australia. The conclusions were published last week in the journal iScience.

You’re breathing DNA right now

This study is just the latest innovation in the emerging scientific field of the study of environmental DNA (eDNA) – the genetic material that all living creatures lose as they move through the world, often in the form of dead skin cells.

In recent years, scientists have collected DNA from soil, water, plants and more. It can even be fired from the air.

Earlier this year, conservationists used environmental DNA to track down an elusive species of golden mole in South Africa that was feared to be extinct.

“Everything seems to be covered by environmental DNA,” said Elizabeth Clare, a molecular ecologist at York University in Toronto, who was not involved in the study. “Every breath of air you breathe contains DNA.”

A large spider with large red legs and white nodules on its black body walks on a web.
An Austracantha minax spider spins a web at Karakamia Sanctuary, the wildlife reserve where Newton and his colleagues conducted the first part of their study. (Submitted by Joshua Newton)

Newton says the idea to check spider webs for animal DNA came from his thesis advisor, Morten Allentoft.

“He was walking in a wetland near our house and saw a giant web, and it just clicked. And he was like, ‘Oh, this is definitely going to work.'”

Scientists have used webs to collect DNA before, but only that of the spiders that built them and the insects they feed on. This is the first time researchers have extracted invertebrate DNA from webs.

They first collected webs from a wildlife sanctuary in Perth and identified DNA from 32 different species, including native mammals and birds.

But scientists don’t know how far eDNA travels, or how long it lasts, so the researchers couldn’t be certain that the DNA they found came from animals currently living nearby.

So they repeated the experiment at Perth Zoo. Sure enough, they found DNA from 61 different invertebrate species that, overall, matched the zoo’s makeup.

“So there are elephants and rhinos and kangaroos in the spider webs,” Newton said.

Clare says that by conducting their research in a zoo – where they knew exactly where the animals were in relation to the webs – the study authors helped unravel some of the mysteries of eDNA.

“We really lack information about how far the (genetic) material travels and how it persists,” she said. “So, scientifically, the most interesting thing is that it helps us refine the idea of ​​where it can move and how far it can go.”

Fast, cheap and easy

Mark Louie Lopez, a researcher at the University of Victoria who works with First Nations to monitor eDNA in Alberta lakessays using webs to collect DNA is a smart innovation.

He often says that collecting genetic material on land means swabbing trees and leaves, taking soil samples, or studying blood-sucking creatures like leeches and mosquitoes.

“Collecting spider webs is a considerably faster method…and it also avoids problems caused by the presence of organic inhibitors (e.g. tannins found in soil) that make DNA detection more difficult ” said Lopez, a postdoctoral researcher at iTrackDNA and Liber Ero. CBC in an email.

“It’s amazing how creative researchers have been in using eDNA for biodiversity monitoring.”

Clare and Lopez caution that eDNA alone is limited in scope. For example, you can know which animals are around, but not how many. So when it comes to measuring biodiversity, it is just one tool in the scientific toolbox.

Currently, one of the most effective methods for collecting airborne DNA is to extract it from air filters. a technique developed by Clare and colleagues.

WATCH | York University scientists collect eDNA from air filters:

But filters require electricity. And scientists must either install them or collaborate with countries and governments that already operate them.

“It’s a little simpler,” Newton said. “We just walk through the environment and the cobwebs are right there and they’re very easy to collect. And they’re pretty much everywhere, cobwebs.”

Everyone wins, he says, except maybe the hard-working spiders.

“It would be nice to find something that works this well and doesn’t impact the spider,” Newton said. “We’re working on it.”

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