Shark tooth DNA reveals species involved in bite

Whenever we go in the ocean, we’re going into a different environment, and we share that environment with many other organisms. There were a couple of shark bites in New York. In one of the victims, a small piece of shark’s tooth was embedded in the wound, but this one’s actually broken, and some of the very distinctive characteristics are missing. Authorities in New York sent the tooth to us to see if we’re able to get any DNA from it. This is the tooth. It’s very tiny. The inside portion actually has a blood supply. And that’s the part that we might be able to get some DNA from. We extracted some tissue from deep inside the pulp that wouldn’t have been contaminated. We took that tissue, we extracted DNA, we sequenced that DNA, and then we compared that DNA with a reference database that we maintain here at the University of Florida. We were able to determine the tooth came from a sand tiger shark. We believe that this is the first time that DNA has been used to identify the shark that’s bitten somebody. We work with molecular data and DNA sequences. We try to estimate phylogenies. We do a lot of very academic exercises. And here is a situation where we can use the knowledge that we’ve gained in a very practical way. Whenever there’s a shark in the water, they’re not going to hunt you down and bite you. What I want people to understand about sharks is these are fascinating animals about which we know practically nothing. We don’t know why their DNA evolves so slowly. We don’t know how they can go into freshwater, and then back into saltwater. That’s a ridiculous thing that they can do, effortlessly. If the Loch Ness monster was next to you, would you be excited or would you be frightened? I’d be both. These things are amazing and yet we’ve all learned to fear them. Humans have been around for about 3 million years, and sharks, as a lineage, for 400 million years. They’re 100 times older than we are– that’s what’s interesting. You’re swimming next to a living fossil. That’s unusual.

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