The air in a zoo is stuffed with smells, from the fish used for feed to the manure from the grazing herbivores, however now we all know it’s also filled with DNA from the animals residing there. In the journal Current Biology on January 6th, two analysis teams have every revealed an unbiased proof-of-concept research exhibiting that by sampling air from an area zoo, they’ll acquire sufficient DNA to determine the animals close by. This might show to be a beneficial, non-invasive software to trace biodiversity.
“Capturing airborne environmental DNA from vertebrates makes it possible for us to detect even animals that we cannot see are there,” says researcher Kristine Bohmann and head of the staff at the University of Copenhagen.
Terrestrial animals might be monitored in some ways: straight by digicam and in-person remark, or not directly by what they depart behind, like footprints or feces. The downside to those strategies is that they’ll contain intensive fieldwork and require the animal to be bodily current. For instance, monitoring animals by digicam requires information of the place to place the cameras on the animal’s path, sifting by way of hundreds of images, and often a little bit of luck.
“Earlier in my career, I went to Madagascar hoping to see lots of lemurs. But in reality, I rarely saw them. Instead, I mostly just heard them jumping away through the canopy.” says Bohmann. “So, for many species it can be a lot of work to detect them by direct observation, especially if they are elusive and live in very closed or inaccessible habitats.”
“Compared to what people find in rivers and lakes, monitoring airborne DNA is really, really hard, because the DNA seems super diluted in the air,” says Elizabeth Clare, lead researcher of the Queen Mary University of London staff (Clare is now at York University in Toronto). “But our zoo studies have yet to fail for different samplers, genes, locations, and experimental approaches. All of it worked and surprisingly well.”
Bohmann and Clare draw closely from their previous analysis monitoring wildlife by accumulating different pattern sorts containing DNA shed by animals. This is known as “environmental DNA,” or eDNA, and is a well-established approach used most continuously to watch aquatic organisms by sequencing eDNA from water samples.
“Air surrounds everything, and we wanted to avoid contamination in our samples while optimizing true detection of animal DNA,” says Bohmann. “Our newest work with airborne eDNA involves what we usually do when processing eDNA samples, just tuned up a little bit.”
Each analysis group carried out their research at an area zoo by accumulating samples at varied locations in the zoo, together with inside walled-in enclosures like the tropical home and indoor stables, in addition to outside enclosures in the open air. “To collect airborne eDNA, we used a fan, like one you would use to cool down a computer, and attached a filter to it. We then let it run for some time,” says Christina Lynggaard, first writer and postdoctoral fellow at the University of Copenhagen.
The fan attracts in air from the zoo and its environment, which might comprise genetic materials from any variety of sources, like breath, saliva, fur, or feces, although the researchers haven’t decided the actual supply. “It could be anything that can become airborne and is small enough to continue floating in the air,” says Lynggaard. “After air filtration, we extracted the DNA from the filter and used PCR amplification to make a lot of copies of the animal DNA. After DNA sequencing, we processed the millions of sequences and ultimately compared them to a DNA reference database to identify the animal species.”
“There’s a leap of faith component to some of this because when you deal with regular tissue or even aquatic DNA samples, you can measure how much DNA you have, but with these samples we’re dealing with forensically tiny amounts of DNA,” says Clare. “In many cases, when we only sample for a few minutes we can’t measure the DNA, and so we have to jump to the next stage of PCR where we find out whether there’s any in it or not. When we sample for hours we get more but there is a tradeoff.”
In every research, the researchers detected animals inside the zoo and wildlife from the close by. Clare’s staff from Queen Mary University of London detected DNA from 25 species of mammals and birds, and even DNA belonging to the Eurasian hedgehog, which is endangered in the UK. Bohmann’s staff at the University of Copenhagen staff detected 49 non-human vertebrate species, together with mammal, hen, reptile, amphibian, and fish species. These included zoo animals like the okapi and armadillo and even the guppy in a pond in the tropical home, domestically occurring animals like squirrels, and pest animals like the brown rat and home mouse. Further, they detected fish species used for feed for different animals in the zoo. Both groups took intensive measures to verify that their samples weren’t contaminated, together with by DNA already of their labs.
By selecting a zoo for the location of their research, the researchers knew the place of a big assortment of non-native species, so they might inform the distinction between an actual sign and a contaminant. “We had originally thought of going to a farm, but if you pick up cow DNA you must ask ‘Is that cow here or is it some cow a hundred miles away or in someone’s lunch?’” says Clare. “But by using the zoo as a model there’s no other way I would detect DNA from a tiger, except for the zoo’s tiger. It lets us really test the detection rates.”
“One thing both our labs do is develop and apply new tools, so perhaps it’s not so surprising that we both ended up with the same idea at the same time,” says Clare.
However, the indisputable fact that each analysis teams are publishing at the similar time in the journal Current Biology is way from coincidental. After seeing one another’s articles on a preprint server, the two teams determined to submit their manuscripts to the journal collectively collectively. “We decided we would rather take a bit of a gamble and say we’re not willing to compete on this,” says Clare. “In fact, it’s such a crazy idea, we’re better off having independent confirmations that this works. Both teams are very eager to see this technique develop.”
Reference: “Airborne environmental DNA for terrestrial vertebrate community monitoring” by Christina Lynggaard, Mads Frost Bertelsen, Casper V. Jensen, Matthew S. Johnson, Tobias Guldberg Frøslev, Morten Tange Olsen and Kristine Bohmann, 6 January 2022, Current Biology.
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