Morten Allentoft
Joshua Newton, a doctoral student at Curtin University’s School of Molecular and Life Sciences near Perth, collecting a golden orb spiderweb.
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Spiders create silken webs to ensnare flies and other small creatures. They are also inadvertently capturing a diverse range of DNA from the surrounding environment, a hidden resource that Australian researchers say could be utilized for tracking endangered animals and monitoring ecosystems.
Among spiderwebs collected from Perth Zoo and the Karakamia woodland sanctuary in Western Australia, genetic traces of 93 animals were identified, including native kangaroos, koalas, elephants, and zebras, according to a study published in the journal iScience.
Joshua Newton, a coauthor of the study and a doctoral student at Curtin University’s School of Molecular and Life Sciences, expressed that spiderwebs could serve as a valuable tool for monitoring local animal populations, a resource often overlooked in biodiversity studies.
Newton stated, “These webs, often overlooked in biodiversity studies, proved to be reservoirs of genetic information. With only trace amounts of DNA needed to identify animals, this cheap and non-invasive method could be a game-changer in how we explore and protect our terrestrial biodiversity.”
All organisms leave behind genetic remnants such as skin cells, hair, or bodily fluids, known as environmental DNA (eDNA). Scientists have previously detected animal DNA in the air. Two proof-of-concept studies published in 2022 recovered DNA from air samples collected at Copenhagen Zoo in Denmark and Hamerton Zoo Park in the United Kingdom.
The Australian study takes this concept a step further, eliminating the need for specific equipment, such as a fan or air filter, to collect the sample.
Spiderwebs are widespread in various natural and human-made environments, found in numerous microhabitats worldwide, naturally serving as adhesive traps, the researchers explained.
Additionally, collecting spiderwebs is a straightforward process. Newton likened it to the scene in Shrek where Princess Fiona makes a spiderweb fairy floss for Shrek, emphasizing the simplicity of the collection procedure. He further explained, “I bring it back into the lab and then we take the DNA off of it using pretty standard extraction methods.”
Environmental DNA techniques have significantly impacted various scientific fields. Archaeologists are utilizing eDNA found in cave dirt to comprehend ancient human populations, while eDNA from Arctic soil cores has revealed ancient animal migration patterns.
The method is also used in conservation efforts, as evidenced by the rediscovery of the blind golden mole using eDNA 87 years after wildlife experts believed the species had gone extinct.
Similar techniques are employed to sample eDNA in sewage to detect and monitor diseases such as Covid-19 in human populations.
Elizabeth Clare, a professor at York University, Canada, who led one of the 2022 eDNA studies, commended the use of spiderwebs, emphasizing its non-invasive nature.
She mentioned, “It’s wonderfully non-invasive (unless you are the spider!). It does not surprise me at all that it works,”
Species detected at Perth Zoo ranged from the pygmy marmoset to the Asian elephant. The study detected animals with diverse behaviors and lifestyles, including nocturnal, arboreal, ground-dwelling, and animals with varied skin coverings such as fur, feathers, scales, and naked skin.
The authors noted a disparity in the number of species detected between the zoo and the woodland sanctuary, attributing this difference to the higher animal density at the zoo.
The study also pointed out that the types of spiderwebs collected can affect the types and quantity of DNA gathered. Different types of spiderwebs may be suited to specific analyses.
Next, the team aims to compare spiderwebs with other materials, like soil and water, which absorb or collect eDNA. They also plan to investigate the distance DNA can travel within various environments.
