The air in a zoo has lots of smells, from the fish utilized for feed to the manure from the grazing herbivores, today we understand it is likewise loaded with DNA from the animals living there. In the journal Current Biology on January 6 th, 2 research study groups have actually each released an independent proof-of-concept research study revealing that by tasting air from a regional zoo, they can gather sufficient DNA to determine the animals close by. This might show to be an important, non-invasive tool to track biodiversity.
“Capturing airborne environmental DNA from vertebrates makes it possible for us to detect even animals that we cannot see are there,” states scientist Kristine Bohmann and head of the group at the University of Copenhagen.
Terrestrial animals can be kept an eye on in lots of methods: straight by video camera and in-person observation, or indirectly by what they leave, like footprints or feces. The disadvantage to these techniques is that they can include extensive fieldwork and need the animal to be physically present. For example, keeping an eye on animals by video camera needs understanding of where to put the video cameras on the animal’s course, sorting through countless photos, and generally a little 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.” statesBohmann “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,” states Elizabeth Clare, lead scientist of the Queen Mary University of London group (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 greatly from their previous research study tracking wildlife by gathering other sample types consisting of DNA shed by animals. This is described as “environmental DNA,” or eDNA, and is a reputable method utilized most often to keep track of marine 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,” statesBohmann “Our newest work with airborne eDNA involves what we usually do when processing eDNA samples, just tuned up a little bit.”
Each research study group performed their research study at a regional zoo by gathering samples at different locations in the zoo, consisting of 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,” states Christina Lynggaard, very first author and postdoctoral fellow at the University of Copenhagen.
The fan attracts air from the zoo and its environments, which might include hereditary product from any variety of sources, like breath, saliva, fur, or feces, though the scientists have actually not figured out the precise source. “It could be anything that can become airborne and is small enough to continue floating in the air,” statesLynggaard “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,” statesClare “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 each research study, the scientists spotted animals inside the zoo and wildlife from the neighboring. Clare’s group from Queen Mary University of London spotted DNA from 25 types of mammals and birds, and even DNA coming from the Eurasian hedgehog, which is threatened in the UK. Bohmann’s group at the University of Copenhagen group spotted 49 non-human vertebrate types, consisting of mammal, bird, reptile, amphibian, and fish types. These consisted of zoo animals like the okapi and armadillo and even the guppy in a pond in the tropical home, in your area happening animals like squirrels, and insect animals like the brown rat and home mouse. Further, they spotted fish types utilized for feed for other animals in the zoo. Both groups took substantial steps to examine that their samples were not infected, consisting of by DNA currently in their laboratories.
By picking a zoo for the place of their research studies, the scientists understood the position of a big collection of non-native types, so they might discriminate in between a genuine signal and a pollutant. “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?’” statesClare “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,” states Clare.
However, the reality that both research study groups are releasing at the very same time in the journal Current Biology is far from coincidental. After seeing each other’s short articles on a preprint server, the 2 groups chose to send their manuscripts to the journal together collectively. “We decided we would rather take a bit of a gamble and say we’re not willing to compete on this,” statesClare “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 Fr øslev, Morten Tange Olsen and Kristine Bohmann, 6 January 2022, Current Biology
DOI: 10.1016/ j.cub.202112014