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Wikimedia Commons
Wikimedia Commons

This Caterpillar’s Stink Breath Keeps the Spiders Away

Wikimedia Commons
Wikimedia Commons

Bad breath usually won’t win you many friends, but at least it will keep your enemies at arm’s length, too. The larval caterpillar form of a moth called the tobacco hornworm, scientists have discovered, uses a blast of nasty air to fend off wolf spiders and other predators. The source of the stench is the hornworm’s preferred meal: tobacco leaves. 

While human smokers look to nicotine as a stimulant, the tobacco plants it comes from use it as a defense against insects and other animals that would eat them. Nicotine is a poison, and an exceptionally fast-acting one, racing from the lungs to the brain in just seven seconds after inhalation. At a dose of 30 to 60 milligrams, it can cause convulsions, respiratory failure, and death (smokers only get about 1mg of it from each cigarette, FYI). 

Nasty stuff, and a good reason why most animals don’t munch on tobacco too much. The hornworm has a workaround for this, though, and can tolerate doses of nicotine hundreds of times higher than what would kill most other animals. Even the hornworm doesn’t hang on to the poison for long, though, and rapidly disposes of most of the nicotine in its waste. While getting rid of the nicotine, it can use a little bit of its food’s chemical weaponry as its own, and a team of German ecologists show in a new study how hornworms dispose of the chemical in an alternate way that helps defend them from predators. 

The researchers, from the Max Planck Institute for Chemical Ecology, found that a gene called CYP6B46 redirects some of the nicotine from the hornworm’s gut into their hemolymph, the arthropod analogue of blood, where it hinders and kills parasites. From the hemolymph, the nicotine can also be exhaled through breathing holes on the hornworm’s body called spiracles, creating a spider-repelling “defensive halitosis.”

Here’s a poor hornworm with its CYP6B46 gene silenced. The spider chows down on it without a second thought.  

And here’s a spider versus a normal caterpillar and its noxious nicotine breath. After a face full of that, the spider tries to make a getaway up the side of the Dixie cup. 

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NUS Environmental Research Institute, Subnero
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technology
Researchers in Singapore Deploy Robot Swans to Test Water Quality
NUS Environmental Research Institute, Subnero
NUS Environmental Research Institute, Subnero

There's something peculiar about the new swans floating around reservoirs in Singapore. They drift across the water like normal birds, but upon closer inspection, onlookers will find they're not birds at all: They're cleverly disguised robots designed to test the quality of the city's water.

As Dezeen reports, the high-tech waterfowl, dubbed NUSwan (New Smart Water Assessment Network), are the work of researchers at the National University of Singapore [PDF]. The team invented the devices as a way to tackle the challenges of maintaining an urban water source. "Water bodies are exposed to varying sources of pollutants from urban run-offs and industries," they write in a statement. "Several methods and protocols in monitoring pollutants are already in place. However, the boundaries of extensive assessment for the water bodies are limited by labor intensive and resource exhaustive methods."

By building water assessment technology into a plastic swan, they're able to analyze the quality of the reservoirs cheaply and discreetly. Sensors on the robots' undersides measure factors like dissolved oxygen and chlorophyll levels. The swans wirelessly transmit whatever data they collect to the command center on land, and based on what they send, human pilots can remotely tweak the robots' performance in real time. The hope is that the simple, adaptable technology will allow researchers to take smarter samples and better understand the impact of the reservoir's micro-ecosystem on water quality.

Man placing robotic swan in water.
NUS Environmental Research Institute, Subnero

This isn't the first time humans have used robots disguised as animals as tools for studying nature. Check out this clip from the BBC series Spy in the Wild for an idea of just how realistic these robots can get.

[h/t Dezeen]

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iStock
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science
There May Be an Ancient Reason Why Your Dog Eats Poop
iStock
iStock

Dogs aren't known for their picky taste in food, but some pups go beyond the normal trash hunting and start rooting around in poop, whether it be their own or a friend's. Just why dogs exhibit this behavior is a scientific mystery. Only some dogs do it, and researchers aren't quite sure where the impulse comes from. But if your dog is a poop eater, it's nearly impossible to steer them away from their favorite feces.

A new study in the journal Veterinary Medicine and Science, spotted by The Washington Post, presents a new theory for what scientists call "canine conspecific coprophagy," or dogs eating dog poop.

In online surveys about domestic dogs' poop-eating habits completed by thousands of pet owners, the researchers found no link between eating poop and a dog's sex, house training, compulsive behavior, or the style of mothering they received as puppies. However, they did find one common link between the poop eaters. Most tended to eat only poop that was less than two days old. According to their data, 85 percent of poop-eaters only go for the fresh stuff.

That timeline is important because it tracks with the lifespan of parasites. And this led the researchers to the following hypothesis: that eating poop is a holdover behavior from domestic dogs' ancestors, who may have had a decent reason to tuck into their friends' poop.

Since their poop has a high chance of containing intestinal parasites, wolves poop far from their dens. But if a sick wolf doesn't quite make it out of the den in time, they might do their business too close to home. A healthier wolf might eat this poop, but the parasite eggs wouldn't have hatched within the first day or two of the feces being dropped. Thus, the healthy wolf would carry the risk of infection away from the den, depositing the eggs they had consumed away in their own, subsequent bowel movements at an appropriate distance before the eggs had the chance to hatch into larvae and transmit the parasite to the pack.

Domestic dogs may just be enacting this behavior instinctively—only for them, there isn't as much danger of them picking up a parasite at home. However, the theory isn't foolproof. The surveys also found that so-called "greedy eaters" were more likely to eat feces than dogs who aren't quite so intense about food. So yes, it could still be about a poop-loving palate.

But really, it's much more pleasant to think about the behavior as a parasite-protection measure than our best pals foraging for a delicious fecal snack. 

[h/t The Washington Post]

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