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Image credit: Aziz Aboobaker, Edinburgh

The Tardigrade’s Extraordinary Weirdness Continues

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Image credit: Aziz Aboobaker, Edinburgh

The mystery of the tardigrade—a.k.a. moss piglet, a.k.a. water bear—is one step closer to a solution. Scientists studying the microscopic animals' DNA say the tough, many-legged creatures may be distantly related to nematodes and other "wormy things." The researchers published their findings in the journal PLOS Biology.

Tardigrades are some of the strangest, most badass organisms on Earth. Don't be fooled by their tiny size—these animals are anything but delicate. They can survive in the most brutal conditions, from dehydration and starvation to burning heat, blistering cold, intense radiation, and even the vacuum of space.

How they pull off this near-invincibility is, naturally, a question of some interest among biologists (and to Mental Floss—links to our many articles about these amazing creatures are found throughout this story).

The authors of one 2015 study made headlines when they announced that one-sixth of the tardigrade's genetic blueprint had been swiped from bacteria and other organisms. This horizontal gene transfer (HGT) is not unheard of in nature, but other tardigrade experts, including a team at the University of Edinburgh, felt that 17.5 percent seemed suspiciously high, even for a maverick like the tardigrade.

The skeptics were right. Additional investigation into the tardigrade genome confirmed the presence of a few horizontally transferred genes. Just a few.

HGT aside, there's still plenty to discover in the tardigrade's genes. Tardigrades have been tardigrades for hundreds of millions of years. No fossils remain from their early days to tell us what they might have been before. We don't really know where they came from, evolutionarily speaking, or who their relatives are.

To find out, Edinburgh researcher Mark Blaxter and his colleagues picked apart the genomes of two tardigrade species, Ramazzottius varieornatus and Hypsibius dujardini. They found something unexpected: The armored, many-legged tardigrades seemed more closely related to worms than to insects.

If these findings are accurate, Blaxter told Mental Floss in an email, they challenge the very structure of the Panarthropoda family tree, which assumes "the leggy moulting animals are more closely related to each other than they are to wormy things like nematodes."

But he notes that there's lots more research to be done before issuing that challenge: "We have only looked at a tiny fraction of the 10 or more million species on Earth. Every new group, and possibly every species, will have something exciting in it we haven't seen before, and didn't imagine."

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Big Questions
Why Can't Dogs Eat Chocolate?
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Even if you don’t have a dog, you probably know that they can’t eat chocolate; it’s one of the most well-known toxic substances for canines (and felines, for that matter). But just what is it about chocolate that is so toxic to dogs? Why can't dogs eat chocolate when we eat it all the time without incident?

It comes down to theobromine, a chemical in chocolate that humans can metabolize easily, but dogs cannot. “They just can’t break it down as fast as humans and so therefore, when they consume it, it can cause illness,” Mike Topper, president of the American Veterinary Medical Association, tells Mental Floss.

The toxic effects of this slow metabolization can range from a mild upset stomach to seizures, heart failure, and even death. If your dog does eat chocolate, they may get thirsty, have diarrhea, and become hyperactive and shaky. If things get really bad, that hyperactivity could turn into seizures, and they could develop an arrhythmia and have a heart attack.

While cats are even more sensitive to theobromine, they’re less likely to eat chocolate in the first place. They’re much more picky eaters, and some research has found that they can’t taste sweetness. Dogs, on the other hand, are much more likely to sit at your feet with those big, mournful eyes begging for a taste of whatever you're eating, including chocolate. (They've also been known to just swipe it off the counter when you’re not looking.)

If your dog gets a hold of your favorite candy bar, it’s best to get them to the vet within two hours. The theobromine is metabolized slowly, “therefore, if we can get it out of the stomach there will be less there to metabolize,” Topper says. Your vet might be able to induce vomiting and give your dog activated charcoal to block the absorption of the theobromine. Intravenous fluids can also help flush it out of your dog’s system before it becomes lethal.

The toxicity varies based on what kind of chocolate it is (milk chocolate has a lower dose of theobromine than dark chocolate, and baking chocolate has an especially concentrated dose), the size of your dog, and whether or not the dog has preexisting health problems, like kidney or heart issues. While any dog is going to get sick, a small, old, or unhealthy dog won't be able to handle the toxic effects as well as a large, young, healthy dog could. “A Great Dane who eats two Hershey’s kisses may not have the same [reaction] that a miniature Chihuahua that eats four Hershey’s kisses has,” Topper explains. The former might only get diarrhea, while the latter probably needs veterinary attention.

Even if you have a big dog, you shouldn’t just play it by ear, though. PetMD has a handy calculator to see just what risk levels your dog faces if he or she eats chocolate, based on the dog’s size and the amount eaten. But if your dog has already ingested chocolate, petMD shouldn’t be your go-to source. Call your vet's office, where they are already familiar with your dog’s size, age, and condition. They can give you the best advice on how toxic the dose might be and how urgent the situation is.

So if your dog eats chocolate, you’re better off paying a few hundred dollars at the vet to make your dog puke than waiting until it’s too late.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
Elusive Butterfly Sighted in Scotland for the First Time in 133 Years

Conditions weren’t looking too promising for the white-letter hairstreak, an elusive butterfly that’s native to the UK. Threatened by habitat loss, the butterfly's numbers have dwindled by 96 percent since the 1970s, and the insect hasn’t even been spotted in Scotland since 1884. So you can imagine the surprise lepidopterists felt when a white-letter hairstreak was seen feeding in a field in Berwickshire, Scotland earlier in August, according to The Guardian.

A man named Iain Cowe noticed the butterfly and managed to capture it on camera. “It is not every day that something as special as this is found when out and about on a regular butterfly foray,” Cowe said in a statement provided by the UK's Butterfly Conservation. “It was a very ragged and worn individual found feeding on ragwort in the grassy edge of an arable field.”

The white-letter hairstreak is a small brown butterfly with a white “W”-shaped streak on the underside of its wings and a small orange spot on its hindwings. It’s not easily sighted, as it tends to spend most of its life feeding and breeding in treetops.

The butterfly’s preferred habitat is the elm tree, but an outbreak of Dutch elm disease—first noted the 1970s—forced the white-letter hairstreak to find new homes and food sources as millions of Britain's elm trees died. The threatened species has slowly spread north, and experts are now hopeful that Scotland could be a good home for the insect. (Dutch elm disease does exist in Scotland, but the nation also has a good amount of disease-resistant Wych elms.)

If a breeding colony is confirmed, the white-letter hairstreak will bump Scotland’s number of butterfly species that live and breed in the country up to 34. “We don’t have many butterfly species in Scotland so one more is very nice to have,” Paul Kirkland, director of Butterfly Conservation Scotland, said in a statement.

Prior to 1884, the only confirmed sighting of a white-letter hairstreak in Scotland was in 1859. However, the insect’s newfound presence in Scotland comes at a cost: The UK’s butterflies are moving north due to climate change, and the white-letter hairstreak’s arrival is “almost certainly due to the warming climate,” Kirkland said.

[h/t The Guardian]

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