DNA From a Shark Tooth Embedded in a Man's Foot for 25 Years Identifies the Culprit

Blacktip shark
Blacktip shark
Sahil Miyani, iStock / Getty Images Plus

It was unclear what species of shark attacked Jeff Weakley while he was surfing off Flagler Beach, Florida in 1994. Whether it was a tiger shark, bull shark, great white shark, or some other predator didn't matter at the time—his priority was swimming to safety before the shark could take another bite.

Twenty-five years later, the wound on Weakley's right foot has healed, and he's had plenty of time to wonder what exactly bit him on that beach trip. By analyzing a tooth fragment that was lodged in his foot for more than two decades, a team of scientists has finally given him an answer, the Ocala StarBanner reports.

Bits of shark tooth have come loose from Weakley's foot several times since he was attacked in 1994. The third time it happened, in fall 2018, he collected the shard and sent it to the Florida Program for Shark Research, a part of the Florida Museum of Natural History in Gainesville. He had just read an article about the program's work identifying shark species using the DNA from their teeth, and he suspected the team might be able to do the same with his tooth fragment.

His hunch was correct: The scientists analyzed the sample and confirmed that the shark that had bit Weakley a quarter-century earlier had been a blacktip shark (Carcharhinus limbatus). That finding was made possible by years of hard work. Over more than two decades, the program has amassed a database of shark DNA containing reference samples for roughly 70 percent of all known shark, skate, ray, and chimera species. Luck was also on their side: The researchers had feared that Weakley's immune system would have destroyed any DNA in the shark's tooth, but when it arrived at the lab, there was enough to make the identification.

Shark attacks are common in movies and TV, but much less so in real life. You're more likely to be struck by lighting or die from the flu than be the victim of a shark attack. When sharks do bite humans, it's often because they've mistaken them for a prey animal, and they'll usually let the victim go once they've realized their error. This is likely how Weakley escaped his shark attack with his foot mostly intact.

[h/t Ocala StarBanner]

Want to Reduce Your Stress In 10 Minutes? Pet a Cat or Dog

Nevena1987/iStock via Getty Images
Nevena1987/iStock via Getty Images

If you know a college student or are one yourself, you might be familiar with the programs that allow students to pet dogs or cats for a few hours, usually during finals season. The hope is that spending a little time with a cuddly creature will take students’ minds off their exams and lower their stress levels. The rising popularity of emotional support animals would seem to uphold that idea, but there hasn’t been much data on the petting sessions' effectiveness—until now.

In a study recently published in the journal AERA Open, Patricia Pendry and Jaymie Vandagriff of Washington State University found that students who pet the animals in one of these animal visitation programs had lower salivary cortisol levels than those who didn’t. (Cortisol is the body’s main stress hormone.)

In their experiment, the researchers split 249 college students into four groups. The first group played with shelter cats and dogs for 10 minutes. The second group stood in line watching the first group hang out with the animals but never got to do it themselves. The third group was shown images of the animals; and the fourth group was told they were on a waitlist to see the animals, but never actually saw them. Each of the students submitted three saliva samples—one when they woke up, one 15 minutes after the 10-minute experiment, and a third 25 minutes after the experiment.

The researchers found that the group of students who got to pet the animals had noticeably lower cortisol levels than the other groups, after controlling for other variables like what their cortisol level had been that morning, how long they had been awake, or differences in their circadian rhythms.

Since it’s only one study with a relatively small sample size of students from one university, it’s not enough to suggest that every anxiety-ridden student can be helped by petting a pup. But it complements other well-documented benefits of owning a dog or cat, and might be a good thing to try whenever you’re feeling a little stressed.

[h/t Science Alert]

England Is Being Invaded By a Swarm of Flying Ants That Can Be Seen From Space

Digoarpi/iStock via Getty Images
Digoarpi/iStock via Getty Images

Last week, the UK's weather service registered what seemed like a system of rain showers moving along the nation’s southern coast. But it wasn’t rain—it was a swarm of flying ants.

Though it sounds like something out of a horror film or the Old Testament, it’s actually a completely normal phenomenon that occurs in the UK every summer when a bout of hot, humid weather follows a period of rainfall, The Guardian reports. Flying ants decide it’s a good time to mate, and the queen takes to the sky, emitting pheromones that attract males.

From there, it’s survival of the fittest. The queen will out-fly most of her suitors, leaving only the strongest males to catch up and mate with her, which ensures the strength of her offspring. The others either lose their wings and fall to the ground, or become bird food. (The ants produce formic acid in their bodies as a defense mechanism, which may make gulls that eat them seem loopy.)

According to Smithsonian.com, the queen will chew off her wings after mating and fall to the ground to start a new colony, and the sperm she collected from that one flight will fertilize her eggs for the rest of her life (which could be up to 15 years in the wild).

The official, rather-romantic term for the annual aerial antics is “nuptial flight,” but locals often refer to it simply as “flying ant day.” It sometimes lasts for weeks, during which billions of the harmless insects can be seen in the skies.

A representative from the Met Office explained that its weather satellites mistook the ants for rain clouds because the radar detects the ants in the same way it sees raindrops. Dr. Adam Hart, an entomologist at the University of Gloucestershire, told The Guardian that he thinks the reason the radar registered the ants this year was a result of better satellite technology rather than an increase in the flying ant population.

[h/t Smithsonian.com]

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