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Bernard Dupont, Flickr // CC BY SA-2.0
Bernard Dupont, Flickr // CC BY SA-2.0

Carnivorous Plant Uses Rain to Spring Its Trap

Bernard Dupont, Flickr // CC BY SA-2.0
Bernard Dupont, Flickr // CC BY SA-2.0

“Rain, rain, go away, come again another day” is not a sentiment that many would disagree with. But then there’s Nepenthes gracilis, a carnivorous plant found in Southeast Asia that relies on rain to help it eat. 

Carnivorous plants thrive in poor soils where most other plants would fail, because they get nutrients from consuming insects instead of taking them from the ground. They can’t stalk, chase, and attack their prey like animal predators, though, so they have to rely on lures and traps. Many of these traps, like the snapping “mouths” of Venus flytraps, take lots of time and energy to reset after use, while others, like the catapulting tentacles of sundews, can only be used once. In a new study, biologist Ulrike Bauer shows that N. gracilis works around these constraints by using rain drops to drive its traps and set them off with no energy costs. 

N. gracilis is a pitcher plant, and captures and digests insects in a modified leaf that looks like a champagne flute. Bugs are lured in by the plant’s smell and the nectar that coats the underside of the pitcher’s lid. While crawling around on the lid and collecting nectar, the bugs get knocked off and into the pitcher, where they’re devoured. 

Instead of flicking its prey into the trap by moving the lid itself, Bauer discovered, the plant lets the impact of rain drops do the work for it. Her study began when she noticed that N. gracilis’s lid is more rigid than those of its cousins. After taking high-speed video of the traps in action and looking at the mechanics of the lids in their lab, Bauer and her collaborators found that N. gracilis’s stiff lid doesn’t bend under the impact of rain drops like other pitcher plant lids do, but pivots on a flexible hinge at its base. That means there’s no safe spot for bugs to avoid getting shaken, like there would be if only part of the lid bent downward. Because the lid is small and light, it moves very quickly, and its rain-driven shaking is faster than both the Venus flytrap’s snapping trap and the sundew’s tentacles. 

All of this happens without any work from the plant. It doesn’t need to set the trap, activate it, and then wait to reset it, but can use it, Bauer writes, “instantly and indefinitely as long as the external driver, rain drop fall, persists.”

Useful as the effortless trap is, it does seem to have one big drawback in that it only works when it's raining. This isn’t too much of a problem for the plant, though, the researchers say. Water can keep dripping from other vegetation above the plants and keep the trap swinging long after a rain shower stops. When there’s no rain, social insects like ants that survive their encounter with the plant can recruit their nest mates to the food source, and they might not be so lucky to come check it out on a dry day. 

N. gracilis’s unique trap shakes up our picture of carnivorous plants, the researchers say. Traditionally, they’ve been divided into two groups: those with “active” moving traps like the Venus flytrap and those with “passive” motionless traps like pitcher plants. N. gracilis has a trap that the researchers call “passive-dynamic,” and uses movement but requires no activity from the plant. It suggests, they write, that the dividing line isn’t so clear and there’s a continuum between active and passive trapping mechanisms, with more traps like this potentially out there waiting to be discovered. 

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Animals
Watch the First-Ever Footage of a Baby Dumbo Octopus
NOAA, Wikimedia Commons // Public Domain
NOAA, Wikimedia Commons // Public Domain

Dumbo octopuses are named for the elephant-ear-like fins they use to navigate the deep sea, but until recently, when and how they developed those floppy appendages were a mystery. Now, for the first time, researchers have caught a newborn Dumbo octopus on tape. As reported in the journal Current Biology, they discovered that the creatures are equipped with the fins from the moment they hatch.

Study co-author Tim Shank, a researcher at the Woods Hole Oceanographic Institution in Massachusetts, spotted the octopus in 2005. During a research expedition in the North Atlantic, one of the remotely operated vehicles he was working with collected several coral branches with something strange attached to them. It looked like a bunch of sandy-colored golf balls at first, but then he realized it was an egg sac.

He and his fellow researchers eventually classified the hatchling that emerged as a member of the genus Grimpoteuthis. In other words, it was a Dumbo octopus, though they couldn't determine the exact species. But you wouldn't need a biology degree to spot its resemblance to Disney's famous elephant, as you can see in the video below.

The octopus hatched with a set of functional fins that allowed it to swim around and hunt right away, and an MRI scan revealed fully-developed internal organs and a complex nervous system. As the researchers wrote in their study, Dumbo octopuses enter the world as "competent juveniles" ready to jump straight into adult life.

Grimpoteuthis spends its life in the deep ocean, which makes it difficult to study. Scientists hope the newly-reported findings will make it easier to identify Grimpoteuthis eggs and hatchlings for future research.

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Animals
15 Confusing Plant and Animal Misnomers
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iStock

People have always given names to the plants and animals around us. But as our study of the natural world has developed, we've realized that many of these names are wildly inaccurate. In fact, they often have less to say about nature than about the people who did the naming. Here’s a batch of these befuddling names.

1. COMMON NIGHTHAWK

There are two problems with this bird’s name. First, the common nighthawk doesn’t fly at night—it’s active at dawn and dusk. Second, it’s not a hawk. Native to North and South America, it belongs to a group of birds with an even stranger name: Goatsuckers. People used to think that these birds flew into barns at night and drank from the teats of goats. (In fact, they eat insects.)

2. IRISH MOSS

It’s not a moss—it’s a red alga that lives along the rocky shores of the northern Atlantic Ocean. Irish moss and other red algae give us carrageenan, a cheap food thickener that you may have eaten in gummy candies, soy milk, ice cream, veggie hot dogs, and more.

3. FISHER-CAT

Native to North America, the fisher-cat isn’t a cat at all: It’s a cousin of the weasel. It also doesn’t fish. Nobody’s sure where the fisher cat’s name came from. One possibility is that early naturalists confused it with the sea mink, a similar-looking creature that was an expert fisher. But the fisher-cat prefers to eat land animals. In fact, it’s one of the few creatures that can tackle a porcupine.

4. AMERICAN BLUE-EYED GRASS

American blue-eyed grass doesn’t have eyes (which is good, because that would be super creepy). Its blue “eyes” are flowers that peek up at you from a meadow. It’s also not a grass—it’s a member of the iris family.

5. MUDPUPPY

The mudpuppy isn’t a cute, fluffy puppy that scampered into some mud. It’s a big, mucus-covered salamander that spends all of its life underwater. (It’s still adorable, though.) The mudpuppy isn’t the only aquatic salamander with a weird name—there are many more, including the greater siren, the Alabama waterdog, and the world’s most metal amphibian, the hellbender.

6. WINGED DRAGONFISH

This weird creature has other fantastic and inaccurate names: brick seamoth, long-tailed dragonfish, and more. It’s really just a cool-looking fish. Found in the waters off of Asia, it has wing-like fins, and spends its time on the muddy seafloor.

7. NAVAL SHIPWORM

The naval shipworm is not a worm. It’s something much, much weirder: a kind of clam with a long, wormlike body that doesn’t fit in its tiny shell. It uses this modified shell to dig into wood, which it eats. The naval shipworm, and other shipworms, burrow through all sorts of submerged wood—including wooden ships.

8. WHIP SPIDERS

These leggy creatures are not spiders; they’re in a separate scientific family. They also don’t whip anything. Whip spiders have two long legs that look whip-like, but that are used as sense organs—sort of like an insect’s antennae. Despite their intimidating appearance, whip spiders are harmless to humans.

9. VELVET ANTS

A photograph of a velvet ant
Craig Pemberton, Wikimedia Commons // CC BY-SA 3.0

There are thousands of species of velvet ants … and all are wasps, not ants. These insects have a fuzzy, velvety look. Don’t pat them, though—velvet ants aren’t aggressive, but the females pack a powerful sting.

10. SLOW WORM

The slow worm is not a worm. It’s a legless reptile that lives in parts of Europe and Asia. Though it looks like a snake, it became legless through a totally separate evolutionary path from the one snakes took. It has many traits in common with lizards, such as eyelids and external ear holes.

11. TRAVELER'S PALM

This beautiful tree from Madagascar has been planted in tropical gardens all around the world. It’s not actually a palm, but belongs to a family that includes the bird of paradise flower. In its native home, the traveler’s palm reproduces with the help of lemurs that guzzle its nectar and spread pollen from tree to tree.

12. VAMPIRE SQUID

Drawing of a vampire squid
Carl Chun, Wikimedia Commons // Public Domain

This deep-sea critter isn’t a squid. It’s the only surviving member of a scientific order that has characteristics of both octopuses and squids. And don’t let the word “vampire” scare you; it only eats bits of falling marine debris (dead stuff, poop, and so on), and it’s only about 11 inches long.

13. MALE FERN & LADY FERN

Early botanists thought that these two ferns belonged to the same species. They figured that the male fern was the male of the species because of its coarse appearance. The lady fern, on the other hand, has lacy fronds and seemed more ladylike. Gender stereotypes aside, male and lady Ferns belong to entirely separate species, and almost all ferns can make both male and female reproductive cells. If ferns start looking manly or womanly to you, maybe you should take a break from botany.

14. TENNESSEE WARBLER

You will never find a single Tennessee warbler nest in Tennessee. This bird breeds mostly in Canada, and spends the winter in Mexico and more southern places. But early ornithologist Alexander Wilson shot one in 1811 in Tennessee during its migration, and the name stuck.

15. CANADA THISTLE

Though it’s found across much of Canada, this spiky plant comes from Europe and Asia. Early European settlers brought Canada thistle seeds to the New World, possibly as accidental hitchhikers in grain shipments. A tough weed, the plant soon spread across the continent, taking root in fields and pushing aside crops. So why does it have this inaccurate name? Americans may have been looking for someone to blame for this plant—so they blamed Canada.

A version of this story originally ran in 2015.

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