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14 Captivating Facts About Carnivorous Plants

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Many, many animals eat plants—but carnivorous plants bite back. Read on to find out why these plants eat meat, why a Venus flytrap knows how to count, and why one plant rents itself out as a bat hotel … in exchange for poop.

1. THERE MIGHT BE CARNIVOROUS PLANTS NEAR YOU.

Don’t panic. Unlike Audrey II in Little Shop of Horrors, real meat-eating plants only eat tiny creatures. Most of them snack on insects and other small organisms, and the largest ones can manage, at the most, a rat. They’re found all over the world, on every continent except Antarctica, and as far north as Alaska and Greenland. Some carnivorous plants even live near large urban centers if they can find the right piece of habitat. This means that you may be able to see some in the wild near you: Just contact a local nature center and ask if they have any programs on carnivorous plants.

2. EATING MEAT HELPS THEM LIVE IN TOUGH PLACES.

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Most plants make their own food largely by basking in the sun, which is a pretty sweet deal. So why would they also catch animal prey? Plants can’t survive on sunlight alone: They also slurp up nutrients, such as nitrogen and phosphorus, with their roots. But carnivorous species live in places where the soil is nutrient-poor. Their meaty diet helps them grow faster and gives them better reproductive success. In fact, it’s such a clever strategy that …

3. CARNIVOROUS PLANTS HAVE EVOLVED AT LEAST NINE SEPARATE TIMES.

Through the course of evolution, plants have stumbled across the carnivorous lifestyle at least nine different times. They’ve even evolved a whole diversity of trapping methods: Snap traps, pitfall traps, sticky goo, and more. These traps are made of leaves—highly modified, specialized leaves.

4. THEY HAVE PRETTY FLOWERS, TOO.

Meat-eating plants don’t just woo animals for food. They also need to attract insects that’ll spread their pollen. That’s why many of them have colorful flowers. To make sure that the pollinators don’t actually become dinner, the plants often hold their blooms high above the leaves and well away from the traps. 

5. SOME OF THEM HAVE TENTACLES.

Byblis filifolia aka the Rainbow Plant. Image credit: Petr Dlouhý via Wikimedia // CC BY-SA 3.0

Several plants catch insects with sticky tentacles. Some of them keep their tentacles motionless; these include Australia’s rainbow plants, which are named for the way that sunlight glints off their sticky goo. Others actively wrap their tentacles around their prey. These include the sundews, which are also named for the way sunlight glints off their sticky goo.  One sundew, Drosera glanduligera, goes the extra mile. Its tentacles snap when touched, catapulting prey into the sticky center of the leaf. See it in action here.

6. SOME ARE LIVING FLYPAPER.

Common butterwort. Image credit: Björn S. via Wikimedia // CC BY-SA 2.0 

Butterworts have flat, sticky leaves that function like a cross between flypaper and a stomach. When insects land on a butterwort’s leaves, they get stuck in goo that’s excreted by sticky glands. The plant releases digestive enzymes and absorbs those tasty bug nutrients. 

7. SOME HAVE PITFALL TRAPS.

Nepenthes burbidgeae. Image credit: JeremiahsCPs via Wikimedia // CC BY-SA 3.0

Many plants catch their food by setting out pit-shaped traps and eating whatever falls in. It’s a popular technique that has appeared at least six separate times over the course of plant evolution. Why doesn’t the prey just crawl out of the trap? The pot-shaped leaves generally have particular adaptations, such as downward-pointing hairs, that make escape difficult at best. A lot of these plants, like the pitcher plants in the genus Nepenthes, contain pools of water that drown and digest their prey. 

8. BUT THEY AREN’T JUST POOLS OF DEATH.

A whole community of aquatic critters thrives inside the pitcher plant pools. For example, frogs—some incredibly tiny—lay their eggs on the pitchers, and their tadpoles grow up swimming in pitcher plant water. And a rich bacterial community helps the pitcher plant digest its food. But the weirdest plant-animal relationship might be …

9. PITCHER PLANTS GIVE BATS A ROOST—IN EXCHANGE FOR POOP.

Photo by @christianziegler Hardwicke's Woolly Bat (Kerivoula hardwickii hardwickii) is a bat which uses the pitchers of Nepenthes hemsleyana as a day roost. Being protected from rain and predators is important for bats. In this mutualistic relationship, t

When the common woolly bat is looking for a rest, it snuggles up inside a pitcher plant’s pitcher-shaped trap. The bat gets a place to sleep, and its poop gives the pitcher plant much-needed nutrients. This is such a good deal that the plant grows two kinds of pitchers: One for snagging bugs, and one for poop. The first kind, which sprouts closer to the ground, is perfumed, slippery, and full of digestive fluid, which makes it perfect for catching and eating bugs. The other type grows higher up and is more like a cozy hotel room. 

And here’s the most amazing part: Those hotel room pitchers have a special reflector dish shape. When the bat uses its sonar system to explore the forest, the plants stand out like a neon VACANCY sign. 

10. SOME CARNIVOROUS PLANTS HAVE SNAP TRAPS.

The most famous type of carnivorous plant is probably the Venus flytrap. Its trapping method looks pretty simple: A bug walks in and the leaf snaps shut like a set of green jaws. But how does the plant know to clamp down on insects and not just, say, dead leaves that fall from above?

It turns out that the Venus flytrap can count. Its gaping maw is full of little trigger hairs. When an insect touches a hair, a timer is set. A crawling insect will probably touch another hair, at which point the trap is sprung. Once five hairs are triggered, the Venus flytrap starts spewing out digestive liquid.

There’s another, less famous plant that uses a similar method to catch its prey. The waterwheel plant is basically an aquatic, rootless Venus flytrap. It eats tiny swimming critters and closes its traps incredibly quickly, considering that it always has a mouth full of water. 

11. SOME USE SUCTION.

True to their name, the aquatic bladderworts are covered in little bladder-like traps. The outsides of the bladders have trigger hairs. When a swimming critter touches a hair, the trap springs open and sucks them in. These bladders work so quickly that scientists need cutting edge high-speed cameras to capture the action. Above the water and far from the carnage, the plants make beautiful, delicate flowers

12. SOME USE LOBSTER TRAPS.

Lobster traps work because they have a funnel-shaped entrance that opens into a larger chamber. It’s easy for a lobster to crawl in, but hard for it to find the exit. Some carnivorous plants catch meals in the same way. Genlisea species seem to use this method; they have root-like leaves with a complicated spiral structure that usher tiny creatures to their doom. 

13. THEY NEED OUR LOVE.

Many carnivorous plant species are at risk. Threats include habitat loss, pollution, and poaching. Yes, you read that right. Just like rhinos and elephants, plants are at risk from poachers who sell them to collectors.

Venus flytraps, for example, live in just a relatively small region around Wilmington, North Carolina. Poachers dig them up and sell the plants for a small amount of cash. The problem has gotten so out of hand that stealing flytraps is now a felony punishable by over a year in jail.

14. DARWIN LOVED THEM SO, SO MUCH.

Drosera allantostigma. Image credit: DevOhm via Wikimedia // CC BY-SA 3.0

To find a great model of carnivorous plant love, we need look no further than Charles Darwin. The famous scientist studied them, published a book on them, and even defended them in letters. In a note to the botanist Asa Gray, Darwin raved about Drosera, a.k.a. the sundews: “Depend on it, you are unjust on the merits of my beloved Drosera: it is a wonderful plant, or rather a most sagacious animal. I will stick up for Drosera to the day of my death.” And in a letter to the geologist Charles Lyell, he declared, “at this present moment I care more about Drosera than the origin of all the species in the world.”

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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Scientists Think They Know How Whales Got So Big
May 24, 2017
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It can be difficult to understand how enormous the blue whale—the largest animal to ever exist—really is. The mammal can measure up to 105 feet long, have a tongue that can weigh as much as an elephant, and have a massive, golf cart–sized heart powering a 200-ton frame. But while the blue whale might currently be the Andre the Giant of the sea, it wasn’t always so imposing.

For the majority of the 30 million years that baleen whales (the blue whale is one) have occupied the Earth, the mammals usually topped off at roughly 30 feet in length. It wasn’t until about 3 million years ago that the clade of whales experienced an evolutionary growth spurt, tripling in size. And scientists haven’t had any concrete idea why, Wired reports.

A study published in the journal Proceedings of the Royal Society B might help change that. Researchers examined fossil records and studied phylogenetic models (evolutionary relationships) among baleen whales, and found some evidence that climate change may have been the catalyst for turning the large animals into behemoths.

As the ice ages wore on and oceans were receiving nutrient-rich runoff, the whales encountered an increasing number of krill—the small, shrimp-like creatures that provided a food source—resulting from upwelling waters. The more they ate, the more they grew, and their bodies adapted over time. Their mouths grew larger and their fat stores increased, helping them to fuel longer migrations to additional food-enriched areas. Today blue whales eat up to four tons of krill every day.

If climate change set the ancestors of the blue whale on the path to its enormous size today, the study invites the question of what it might do to them in the future. Changes in ocean currents or temperature could alter the amount of available nutrients to whales, cutting off their food supply. With demand for whale oil in the 1900s having already dented their numbers, scientists are hoping that further shifts in their oceanic ecosystem won’t relegate them to history.

[h/t Wired]

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