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Spiders spin silken webs to catch flies and other tiny prey. They are also capturing a wealth of DNA from the surrounding environment, a hidden resource Australian scientists say could be used to track endangered animals and monitor ecosystems.
Spiders collected from two sites around Perth in Western Australia – Perth Zoo and the Karakamia woodland sanctuary – revealed the genetic signature of 93 animals, including native kangaroos and koalas and captive elephants and zebras, according to a study published this week. last published in iScience magazine.
Spiders may be a useful way to keep track of the animals around us, according to study co-author Joshua Newton, a doctoral student at Curtin University’s School of Molecular and Life Sciences near Perth.
“These networks are often reservoirs of genetic information, often overlooked in biodiversity studies,” Newton said in a press release.
“Requiring only traces of DNA to identify animals, this cheap and non-invasive method could revolutionize the way we explore and protect our terrestrial biodiversity.”
All organisms leave behind fragments of DNA in the form of skin cells, hair or body fluids, and this genetic material is called environmental DNA or eDNA.
Scientists were able to detect animal DNA in the air. Two proof-of-concept studies published in 2022 recovered multi-animal DNA from air samples collected from Copenhagen Zoo in Denmark and Hamerton Zoo in the United Kingdom.
The Australian study takes the idea a step further, eliminating the need for any equipment, such as a fan or air filter, to collect the sample.
Webs, the authors said, are “ubiquitous in many natural and anthropogenic environments, found in a variety of microhabitats around the world, and naturally selected to act as adhesive traps.”
In addition, spiders are really easy to collect, Newton said. “I like it when Princess Fiona in Shrek makes Shrek a spider fairy floss. She just takes a stick and wraps it all up. That’s basically what I do,” he explained. “I bring it back into the lab and then we extract the DNA from it using pretty standard extraction methods.”
eDNA-related techniques are already having a significant impact across different areas of scientific research. Archaeologists are using eDNA found in cave dirt to understand ancient human populations, and eDNA from the heart of the Arctic world has revealed where mammoths and other ice age animals roamed.
It is being used in conservation, and the technique was used to rediscover the blind golden mole, which was found using eDNA 87 years after wildlife experts had feared the species was extinct.
Similar techniques are used to sample eDNA in sewage to detect and track diseases such as Covid-19 in human populations.
Elizabeth Clare, a professor in the biology department at York University in Ontario, Canada, who led one of the 2022 studies on eDNA sampling but was not involved in this research, said she liked the idea of using spiders. .
“It’s incredibly non-invasive (unless you’re the spider!). It doesn’t surprise me at all that it works,” she said via email.
“We’re continuing to look for eDNA from airborne sources and I think that once we get the methods right, airborne eDNA will be very successful,” she said.
Creatures big and small
In Perth Zoo, the species detected ranged in size from the pice marmoset to the Asian elephant. At both sites, the zoo and the Karakamia woodland sanctuary, they were able to spot animals with different behaviors and lifestyles, including the common arboreal possum, ground-dwelling animals such as the giraffe, species night and animals with fur, feathers, scales. and bare skin.
Almost twice as many species were detected at the zoo (61) compared to the woodland (32). The authors said this difference probably existed because the higher density of animals at the zoo increased the chance of detection.
The different types of spiders collected may also affect the types and quantity of DNA collected, the study noted.
In the Karakamia woodland area, 50 kilometers (31 miles) away from the zoo, the team collected more two-dimensional orb webs from the spider families Araneidae and Phonognathidae.
In contrast, the majority of webs collected at Perth Zoo came from the families Desidae and Theridiidae, both with tangled, irregular web arrangements.
Newton said that different types of web may be suitable for specific types of analysis.
“Many of the orb spiders will build their webs in the morning and rebuild them at night,” he said, allowing scientists to collect DNA over a period of time.
Next, the team will look at how spider webs compare to other materials that absorb or collect eDNA, including soil and water..
“I think the big unknown for a lot of (this) is how far the DNA travels.”
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