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]

Shocker: This Electric Eel Delivers More Voltage Than Any Creature on Earth

stacey_newman/iStock via Getty Images
stacey_newman/iStock via Getty Images

Eels are proving to be more slippery than previously believed. A newly identified species of these skinny fish (yes, eels are really fish) delivers more electric voltage than any other creature on the planet.

All species in their taxonomic order (Gymnotiformes) are capable of producing a modest electrical field to help them navigate, a perk that compensates for their poor vision. But electric eels (in the genus Electrophorus) pack a far more potent punch. They bear three organs full of cells that can produce electricity on demand. The cells act as a defense mechanism and can effectively taser prey into submission.

In a study published in Nature Communications, researchers collected more than 100 electric eels in the Amazon region and analyzed their DNA, voltage, and habitat. To their surprise, they found that the single known species of electric eel, Electrophorus electricus, was actually three distinct species. They gave the two new ones the very heavy metal names of E. varii and E. voltai. The latter (named for Alessandro Volta, who invented the electric battery) produced the strongest shock: 860 volts, topping the previous record of 650 volts.

Why the varying strength? The researchers suggested that some eels occupy water with low salt content, and therefore reduced conductivity. A stronger charge may be needed to deliver an effective jolt.

While those numbers sound formidable, their low current means a shock wouldn’t necessarily be harmful to a human. Voltage is the measure of pressure of the flow of electrons; current, or amperage, is the volume of electrons. Eels have high voltage but low current; household power outlets have lower voltage but more current and can be deadly. Eels might startle you with a shock, but it won't be fatal.

If you should find yourself in a school of electric eels bent on subduing you, however, the shocks could result in brief incapacitation that could lead to drowning or an aggravation of an existing heart condition. The study authors hope to eventually film a coordinated eel attack on (non-human) prey.

The discovery of two new species was “quite literally shocking,” lead author Carlos David de Santana told The New York Times.

[h/t Phys.org]

Does the Full Moon Really Make People Act Crazy?

iStock.com/voraorn
iStock.com/voraorn

Along with Mercury in retrograde, the full moon is a pretty popular scapegoat for bad luck and bizarre behavior. Encounter someone acting strangely? Blame it on the lunar phases! It's said that crime rates increase and emergency rooms are much busier during the full moon (though a 2004 study debunked this claim). Plus, there's that whole werewolf thing. Why would this be? The reasoning is that the moon, which affects the ocean's tides, probably exerts a similar effect on us, because the human body is made mostly of water.

This belief that the moon influences behavior is so widely held—reportedly, even 80 percent of nurses and 64 percent of doctors think it's true, according to a 1987 paper published in the Journal of Emergency Medicine [PDF]—that in 2012 a team of researchers at Université Laval's School of Psychology in Canada decided to find out if mental illness and the phases of the moon are linked [PDF].

To test the theory, the researchers evaluated 771 patients who visited emergency rooms at two hospitals in Montreal between March 2005 and April 2008. The patients chosen complained of chest pains, which doctors could not determine a medical cause for the pains. Many of the patients suffered from panic attacks, anxiety and mood disorders, or suicidal thoughts.

When the researchers compared the time of the visits to the phases of the moon, they found that there was no link between the incidence of psychological problems and the four lunar phases, with one exception: in the last lunar quarter, anxiety disorders were 32 percent less frequent. "This may be coincidental or due to factors we did not take into account," Dr. Geneviève Belleville, who directed the team of researchers, said. "But one thing is certain: we observed no full-moon or new-moon effect on psychological problems."

So rest easy (or maybe not): If people seem to act crazy during the full moon, their behavior is likely pretty similar during the rest of the lunar cycle as well.

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