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When to Worry About Mercury in Seafood

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Despite the health benefits of the omega-3 fatty acids and vitamins found in fish, you’ve probably hesitated before taking a bite of that tuna sandwich because of one word: mercury.

Every week seems to bring new and alarming information about the dangers lurking in the cuts of seafood that are supposed to be making us healthier. That’s because mercury, a natural element that fish absorb throughout their lifespan, is a heavy metal that’s been proven toxic to humans in excess doses (human activities, like burning coal and artisanal gold mining, have greatly increased the amount of mercury pollution). Due to its effects on the nervous system—particularly in developing children and pregnant women—restricting your diet to just two 6-ounce servings of low-mercury fish per week has been the longtime recommendation of the Food and Drug Administration (FDA).

Is that too conservative? The answer really depends on you—specifically, your genes. Geneticists believe that some people are capable of expelling mercury from the body more efficiently than others. Since it’s the cumulative effect of the metal in the bloodstream that can cause memory, learning, and behavioral problems, the body’s ability to excrete it can have a significant impact on whether a person will develop systems of exposure. This is one possible reason why a bodybuilder can eat tuna with abandon while actor Jeremy Piven allegedly developed mercury poisoning after a diet rich in sushi.

Since genetic testing is not typically part of a normal physical, a sensible and moderate approach to eating seafood is probably going to work for the majority of the population. The FDA warns that larger fish—shark, swordfish, king mackerel, tilefish—are heavy with the metal and should be avoided in any amount; shrimp, salmon, cod, and canned light tuna are generally safe to eat twice weekly.

(Tuna is, however, typically higher in mercury overall, containing 13 to 58 micrograms per four ounces, while salmon and tilapia typically contain 4 micrograms or less. That discrepancy has led some scientists to caution against anything other than very modest servings of tuna during pregnancy.)

The FDA’s rule applies for pregnant women, and similar guidance exists for children, the elderly, and heavy consumers of fish; fully-developed adults are unlikely to suffer ill effects from adding another serving or two, particularly if they maintain a balance by eating a little less fish the following week.  

While an all-tuna diet could prove harmful, making common-sense choices is your best bet for enjoying the benefits of seafood without the worry.

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Animals
The Shocking Science of Electric Fish
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Like slippery Pokemon, electric eels can produce shocks strong enough to incapacitate large predators. But where do these electric fish get the power to generate such high-voltage attacks?

In a recent video, TED-Ed explains the volatile biology at play. Electric fish like electric eels (which are more closely related to catfish than actual eels) all contain at least one electric organ. This organ is packed with disc-shaped cells called electrocytes. These cells naturally release sodium and potassium ions which create a positive charge inside the cells and a negative charge outside them. But when electric fish send signals from their brains to these organs, it opens up the cells' ion channels, allowing the ions to re-enter. The result is an electrocyte with a positive interior and a negative exterior on one side and a negative interior and a positive exterior on the other—basically a biological battery. Once these cells are charged up, fish can use them to disrupt nearby electric signals, detect other fish, and even paralyze prey.

Fish aren’t the only animals that use electricity to their advantage. The oriental hornet, for example, makes electricity out of sunlight, while some spiders harvest charged particles by coating their webs in electrostatic glue.

[h/t TED-Ed]

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8 Bizarre Creatures That Have Washed Ashore
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With an estimated 95 percent of the world’s oceans yet to be explored, science may never have a complete catalog of the various life forms that navigate their depths. Sometimes, these odd creatures come to us instead. Inclement weather, outside forces, or just plain bad luck have led to some strange sea dwellers washing ashore to confuse—and sometimes terrify—onlookers until they can be identified.

Most recently the fangtooth snake eel, or Aplatophis chauliodus, appeared in Texas to cause a stir following Hurricane Harvey. Here are a few more examples of puzzling creatures that have recently landed in the sand.

1. THE MONTAUK MONSTER // 2008

A screen shot of the Montauk Monster
Nat Geo Wild, YouTube

In July 2008, a photo of what looked like the demon that possessed Sigourney Weaver in Ghostbusters made the internet rounds. “The Montauk Monster,” so named because it was discovered on a beach in Montauk, New York, was a curious-looking carcass that was not immediately identifiable. The animal wasn’t available for autopsy—it was carted away by person or persons unknown—but zoologists asked by media to examine the photo were fairly certain it was a decomposing raccoon that had lost enough hair and skin to reduce its charms considerably. Later, a trio of men from nearby Shelter Island admitted to finding a dead raccoon and giving it a "Viking funeral" by setting it ablaze on the water. Whether that’s true or not, the “monster” was almost certainly the same as the one partial to rooting through your trash.

2. THE INDONESIAN KRAKEN // 2017

Death and decomposition can radically alter the appearance of a species that might otherwise be easily identifiable. Such was the case with the 49-foot-long creature that popped up above the water at Seram Island in Indonesia in May 2017.  The spongy, floating mass was initially mistaken for a giant squid before ocean conservationists pointed out a visible skull, jaw, and spine in some photos, making it far more likely that it was a baleen whale. Although they usually sink to the bottom after expiring, this one might have had bacterial gases keeping it afloat.

3. THE DEMON DOLPHIN OF SAKHALIN // 2015

The corpse that washed up on Sakhalin Island
Mystery Universe, YouTube

Ravaged either by the sea or by some kind of enemy—or both—the rotting corpse of a mystery creature washed up on Sakhalin, an island in Russia, in 2015. Its elongated beak led to early suspicions it was a dolphin, but observers were quick to point out that dolphins don’t have fur. That could’ve been some kind of skin deterioration, but eyewitnesses also claimed to have seen what looked like paws on the specimen. The best bet was that it was a bottlenose whale calf. Before a definitive conclusion was reached, the body washed back out to sea.

4. THE MADBALL OF CAPE TOWN // 2014

The off-putting fish that was found in Cape Town, South Africa
Chaoonnews, YouTube

Looking much like a Cenobite keychain, this fierce little creature was allegedly plucked from the sands of a Cape Town, South Africa resort area by a tourist. Appearing to have a body comprised mostly of a mouth, the fanged horror was photographed and sent along to the University of Cape Town’s biological sciences department. Their best guess? It’s Chorisochismus dentex, or a klipsuier, a nibbler that feeds on mussels. The corpse had dried out, disfiguring its already troubling features.

5. THE NEW ZEALAND SEA MONSTER // 2013

A creature that was a subject of controversy in New Zealand
Djinteressantevideos, YouTube

Roughly 30 feet long, with pointed teeth and a gaping maw, this creature found on New Zealand’s Bay of Plenty looked quite a bit like the logo from Jurassic Park. It was so battered that speculation ran from an alligator to a moray eel. Marine biologist Anton van Helden went on record saying it was likely a killer whale due to its distinctive tail: Orcas can be found in New Zealand.

6. A GIANT EYEBALL // 2012

Very little news that emerges out of Florida could be considered boring. And when things wash ashore there, it’s almost certainly going to capture national attention. In 2012, a perfectly-intact, softball-sized eyeball was found on Pompano Beach, just about 10 miles north of Fort Lauderdale. The eerie, disembodied ocular discovery was forwarded to fish and wildlife researchers, who declared it once belonged to a swordfish. It can be rare to find individual body parts ashore—so why an eye? Because it was appeared to be removed with a knife, experts believe a fisherman cut it out and tossed it in the water.

7. THE MARINE MONSTER // 2012

A South Carolina sturgeon that confused observers
nibiruexists, YouTube

Folly Beach in South Carolina was the site of an alarming discovery in 2012, when a bony-plated fish exceeding 10 feet in length was spotted on shore. The South Carolina Aquarium put speculation to rest by declaring it a sturgeon, a large bony fish with relatives dating back 350 million years—and which has been known to grow to be 500 pounds or more. Their eggs are often used for caviar, though presumably no one raided this one for a gourmet snack.

8. THE ROCH NESS MONSTER // 2015

A fanged sea creature found in England
InformOverload, YouTube

Hollingworth Lake near Littleborough, England sounds like the perfect setting for wonderful childhood memories of boating, fishing, and making lifetime bonds. Unfortunately, it was also briefly a contributor of nightmares, when a 5-foot-long, fanged creature washed up there in 2015. Likely a pike, residents said they had no idea anything so large lived in the water. One called it “something prehistoric.”

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