24-year-old shark attack mystery solved by a tooth pulled from a surfer's foot

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IIn 1994, on Flagler Beach, a picturesque stretch of sand on Florida's Palm Coast, a shark attacked a 21-year-old surfer named Jeff Weakley. He survived with lacerations and a mystery that would not be solved before 24 years. Last fall, when Weakley discovered an article about scientists who used DNA to identify sharks that were attacking humans, the case was finally dismissed.

It was about the same time I pulled the tooth off my foot.

"It was about the same time I removed the tooth from my foot," says Weakley. reverse.

He would have read about a team led by Gavin Naylor, Ph.D., director of the Florida Museum of Natural History's Florida Sharks Research Program, who identified the shark species that had bitten a child off the coast of Florida. Fire Island, New York, 2018. Weakley, now editor-in-chief Florida Sportsman, thought that Naylor's team could identify his attacker with the tooth fragment he had pulled out of the small bulge that was growing on his foot.

He followed Naylor's team, "curious to see if they could use the same DNA process on my sample."

He was lucky. As reported by Naylor and other shark experts in a report Wilderness and environmental medicine study published July 2, the tooth has proved a reliable source of shark DNA, allowing the team to reveal the identity of the attacker.

"We all thought that because the tooth had been in Jeff's body for So long that there was almost no chance of recovering shark DNA, "says Naylor. reverse. "However, we also all thought that it would be fun to try!"

Lei Yang, Ph.D., Laboratory Manager at the FPSR and first author of the new study, worked with Naylor to clean the tooth fragment and scrape its pulp, which had not been degraded by the immune system from Weakley in his previous 24 years. stay in his foot. Yang, who thought this case would be "a long shot", tells reverse that the success of their DNA technique on the sample was unexpected.

"As researchers in museums, we specialize in difficult samples," says Yang. "We were very pleasantly surprised to find that there was still intact DNA that could be used for identification." After extracting and purifying the DNA from the tooth, it was noticeable. team sequenced, comparing sequences to a database of genetic information on sharks and rays.

dental dna — Yang with the tooth fragment, which has surprisingly provided a usable DNA.

According to Naylor, the team generally uses this technique to estimate the evolutionary relationships between different shark species, to understand the structure of their populations, and to reconstruct their historical demography – "in much the same way as that practiced by companies like 23 & Me for human. In a 2015 PNAS study, they apply it to archival river shark specimens of more than a century. Unlike the tooth, these samples had been carefully preserved by a museum and not by a surfer's foot.

The team's success, says Lei, "made us understand that the techniques we use can be more powerful and more generally applicable than we originally thought."

I had suspected for a long time that it was a black tip shark bite and it was satisfying to learn the truth.

In the database, the DNA of the tooth had a clear correspondence: Carcharhinus limbatus, better known as the Blacktip shark. At first, the team was skeptical about the outcome, fearing to have accidentally contaminated the sample. But the DNA they sequenced was compatible with the DNA of other degraded tissues and did not carry a signature suggesting contamination. "In addition," says Naylor, "the sequence fits perfectly with the most abundant species in Flagler County, where Jeff was bitten 24 years earlier."

After 24 years, Weakley's suspicions were confirmed. "I had suspected for a long time that it was a black tip shark bite, and it was satisfying to learn the truth," he says.

DNA is becoming an increasingly useful means of identifying sharks behind attacks on humans, thus indicating specific populations to monitor. As for shark attacks themselves, they seem to be on the rise – but not because sharks seem to be more challenging than usual.

A PLOS One A study published in February showed, using the terrible data from the Florida International Record of Sharks attacks, that shark attack rates have doubled in the last 20 years populated. The authors concluded that sharks did not become more hostile but that more visitors flocked to beaches.

Nevertheless, beach lovers should take into account preventive measures recommended by experts such as Naylor. "Be reasonable," he exhorts. This means that you must follow the rules of the beach, do not swim at dawn or dusk and avoid swimming alone.

Another helpful tip is to stay alert to the strange activities of other marine animals: "Get out of the water if you see large schools of baitfish jumping into shallow waters," he says. "It is very likely that they will be pursued by a predator like a jack or a shark and you would not want to interfere with that interaction."

All these years later, Weakley harbored no resentment towards the shark and continues to surf. The bulge of his foot has disappeared, its content is now a key element in the annals of shark science.

"How do I feel?" I continue to marvel at the achievements of modern science, "says Weakley." I'm happy to think that I may have made a contribution. "

Abstract:

Shark attacks are rare, but when they occur, they arouse substantial interest in the media, the public and others. The consequences of an attack can potentially influence public attitudes towards sharks and the political decisions surrounding the mitigation and conservation of shark attacks. After an attack, the media often arouse interest in determining the shark species involved. This information can satisfy curiosity, complete medical and case records, and inform shark attack mitigation strategies. However, determining the identity of the responsible species is not an easy task.

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