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NOAA OKEANOS EXPLORER Program, Gulf of Mexico 2014 Expedition via Flickr Creative Commons // CC BY 2.0

Cephalopods Evolve Differently From the Rest of Us, Study Finds

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NOAA OKEANOS EXPLORER Program, Gulf of Mexico 2014 Expedition via Flickr Creative Commons // CC BY 2.0

The octopus is an animal with a seemingly endless amount of weird and wonderful traits, all the way down to its DNA. A new report published in the journal Cell has revealed yet another bizarre facet of cephalopod biology: the way they update their genes.

Coeloid cephalopods (that’s octopuses, squid, and cuttlefish) have evolved some truly mind-boggling abilities, from Houdini-like escape to crafting makeshift hunting blinds. They lack the standard optical equipment for color vision, yet scientists believe they can see in color anyway. And where warming waters have weakened other species, cephalopods populations appear to be booming.

The original cephalopod ancestor did not have all these traits. Their unique gifts, like ours, are the result of millions of years of evolution.

Animal evolution works like this: the genetic code of every member of a species is almost identical, but not quite. Each individual has a few DNA mutations that make it unique. When those mutations are advantageous in the environment, their owners will survive, reproduce, and pass the mutated DNA down to the next generation.

We also make changes to our RNA, but these are so scarce—in humans, just a few dozen sites amid roughly 20,000 genes—that their influence is relatively small.

But our rubbery-armed friends have apparently turned this system on its head. Researchers reviewing coeloid genomes say the cephalopods have evolved mostly through small, fluid changes to their RNA, and that their DNA doesn’t look like it’s been updated much at all.

The scientists found that around 11,000 of a squid’s 20,000 genes code for mutable RNA. Octopuses and cuttlefish genetics showed similar ratios, especially in the genes associated with their super-amazing, super-complex nervous systems. Nautiluses, those simpletons of the cephalopod family, looked more like us.

Liscovitch-Brauer et al. 2017. Cell.

Neurobiologist Clifton Ragdale of the University of Chicago was unaffiliated with the research but has worked on cephalopod genetics in the past. Speaking with Scientific American, he said the animals’ bizarro evolution scheme essentially represents “an alternative engine for cephalopod evolution.”

Ragsdale noted that scientists use DNA changes, not RNA, when determining evolutionary history. “This may mean that our molecular clock estimates of when different cephalopod lineages arose and diverged might be too recent. The Nobel Prize–winning biologist Sydney Brenner once said that octopi were the first intelligent beings on Earth. This could prove he was right.”

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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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