Spider webs a useful trap for environmental DNA

Spider webs catch more than flies. It turns out they’re trapping the DNA of far larger animals, which has proven a boon for environmental scientists.

The discovery that environmental DNA (eDNA) – fragments of skin, hair cells or body fluids shed by organisms – is blown into the sticky nets cast by spiders, has one researcher hopeful he’s stumbled upon a cheap and non-invasive way to investigate which animals reside in an ecosystem.

Often, eDNA is obtained by taking samples from aquatic or marine environments, where this organic material becomes suspended in the water column. But spider webs could prove a useful net for scientists seeking out genetic identifiers on land.

Joshua Newton is a PhD candidate at Curtin University’s School of Molecular and Life Sciences. He led the evaluation that drew samples of 49 spider webs cast in a West Australian conservation area and the Perth Zoo.

A frog
A motorbike frog. Credit: Chid Filovitz CC BY-SA 2.0

Analysis of the eDNA collected from the webs showed 85 vertebrate species living across the two sites, including two amphibian species – the motorbike frog (Litoria moorei) and Gunter’s toadlet (Pseudophryne guentheri) – previously unknown at either location.

Unsurprisingly, the eDNA found in spider webs at the zoo was from a high number of non-native species in contrast to the wildlife sanctuary.

Newton is hopeful the discovery that spider webs catch the DNA of vertebrates as well as prey will be a boon for scientists researching the composition of ecosystems.

“With only trace amounts of DNA needed to identify animals, this … could be a game-changer in how we explore and protect our terrestrial biodiversity,” Newton says.

“Spider webs are not just beautiful, they could be our secret weapon to better understanding nature. Our study shows that these webs can help us keep tabs on different animals without disturbing them.”

Newton’s study is published in the journal Science.

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