Why Do Tumbleweeds Tumble? | Deep Look

The silent star of classic Westerns is a plant on a mission. It starts out green and full of life. It even grows flowers. But to reproduce effectively, it needs to turn into a rolling brown skeleton.

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DEEP LOOK is a ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Explore big scientific mysteries by going incredibly small.

Tumbleweeds might be the iconic props of classic Westerns. But in real life, they’re not only a noxious weed, but one that moves around. Pushed by gusts of wind, they can overwhelm entire neighborhoods, as happened recently in Victorville, California, or become a threat for drivers and an expensive nuisance for farmers.

“They tumble across highways and can cause accidents,” said Mike Pitcairn, who tracks tumbleweeds at the California Department of Food and Agriculture in Sacramento. “They pile up against fences and homes.”

And tumbleweeds aren’t even originally from the West.

Genetic tests have shown that California’s most common tumbleweed, known as Russian thistle, likely came from Ukraine, said retired plant population biologist Debra Ayres, who studied tumbleweeds at the University of California, Davis.

A U.S. Department of Agriculture employee, L. H. Dewey, wrote in 1893 that Russian thistle had arrived in the U.S. through South Dakota in flaxseed imported from Europe in the 1870s.

“It has been known in Russia many years,” Dewey wrote, “and has quite as bad a reputation in the wheat regions there as it has in the Dakotas.” This is where the name Russian thistle originates, said Ayres, although tumbleweeds aren’t really thistles.

The weed spread quickly through the United States — on rail cars, through contamination of agricultural seeds and by tumbling.
“They tumble to disperse the seeds,” said Ayres, “and thereby reduce competition.”

By bouncing and rolling, a tumbleweed spreads out tens of thousands of seeds so that they all get plenty of sunlight and space.

Tumbleweeds grow well in barren places like abandoned agricultural fields, vacant lots or the side of the road, where they can tumble unobstructed and there’s no grass, which their seedlings can’t compete with.

— Where does a tumbleweed come from?

Tumbleweeds start out as any plant, attached to the soil. Seedlings, which look like blades of grass with a bright pink stem, sprout at the end of the winter. By summer, Russian thistle plants take on their round shape and grow flowers. Inside each flower, a fruit with a single seed develops.

Other plants attract animals with tasty fruits, and get them to carry away their seeds and disperse them when they poop.

Tumbleweeds developed a different evolutionary strategy. Starting in late fall, they dry out and die, their seeds nestled between prickly leaves. Gusts of wind easily break dead tumbleweeds from their roots and they roll away, spreading their seeds as they go.

— How big do tumbleweeds grow?

Mike Pitcairn, of the California Department of Food and Agriculture, said they can grow to be more than 6 feet tall in parts of the state like the San Joaquin Valley.

— Are tumbleweeds dangerous?

Yes. They can cause traffic accidents, and they can be a fire hazard if they pile up against buildings.

—+ More great Deep Look episodes:

How Ticks Dig In With a Mouth Full of Hooks
https://www.youtube.com/watch?v=_IoOJu2_FKE

This Giant Plant Looks Like Raw Meat and Smells Like Dead Rat
https://www.youtube.com/watch?v=ycUNj_Hv4_Y

Upside-Down Catfish Doesn’t Care What You Think
https://www.youtube.com/watch?v=eurCBOJMrsE

—+ See some great videos and documentaries from the PBS Digital Studios!

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—+ About KQED

KQED, an NPR and PBS affiliate in San Francisco, CA, serves Northern California and beyond with a public-supported alternative to commercial TV, radio and web media.

Funding for Deep Look is provided in part by PBS Digital Studios. Deep Look is a project of KQED Science, which is supported by the Templeton Religion Trust and the Templeton World Charity Foundation, the S. D. Bechtel, Jr. Foundation, the Dirk and Charlene Kabcenell Foundation, the Vadasz Family Foundation, the Gordon and Betty Moore Foundation, the Fuhs Family Foundation Fund and the members of KQED.

Upside-Down Catfish Doesn’t Care What You Think

You might suppose this catfish is sick, or just confused. But swimming belly-up actually helps it camouflage and breathe better than its right-side-up cousins.

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DEEP LOOK: a new ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Get a new perspective on our place in the universe and meet extraordinary new friends. Explore big scientific mysteries by going incredibly small.

Normally, an upside-down fish in your tank is bad news. As in, it’s time for a new goldfish.

That’s because most fish have an internal air sac called a “swim bladder” that allows them to control their buoyancy and orientation. They fill the bladder with air when they want to rise, and deflate it when they want to sink. Fish without swim bladders, like sharks, have to swim constantly to keep from dropping to the bottom.

If an aquarium fish is listing to one side or flops over on its back, it often means it has swim bladder disease, a potentially life-threatening condition usually brought on parasites, overfeeding, or high nitrate levels in the water.

But for a few remarkable fish, being upside-down means everything is great.

In fact, seven species of catfish native to Central Africa live most of their lives upended. These topsy-turvy swimmers are anatomically identical to their right-side up cousins, despite having such an unusual orientation.

People’s fascination with the odd alignment of these fish goes back centuries. Studies of these quizzical fish have found a number of reasons why swimming upside down makes a lot of sense.

In an upside-down position, fish produce a lot less wave drag. That means upside-down catfish do a better job feeding on insect larvae at the waterline than their right-side up counterparts, who have to return to deeper water to rest.

There’s something else at the surface that’s even more important to a fish’s survival than food: oxygen. The gas essential to life readily dissolves from the air into the water, where it becomes concentrated in a thin layer at the waterline — right where the upside-down catfish’s mouth and gills are perfectly positioned to get it.

Scientists estimate that upside-down catfishes have been working out their survival strategy for as long at 35 million years. Besides their breathing and feeding behavior, the blotched upside-down catfish from the Congo Basin has also evolved a dark patch on its underside to make it harder to see against dark water.

That coloration is remarkable because it’s the opposite of most sea creatures, which tend to be darker on top and lighter on the bottom, a common adaptation called “countershading” that offsets the effects of sunlight.

The blotched upside-down catfish’s “reverse” countershading has earned it the scientific name negriventris, which means black-bellied.

— How many kinds of fish swim upside down?

A total of seven species in Africa swim that way. Upside-down swimming may have evolved independent in a few of the species – and at least one more time in a catfish from Asia.

— How do fish stay upright?

They have an air-filled swim bladder on the inside that that they can fill or deflate to maintain balance or to move up or down in the water column.

— What are the benefits of swimming upside down?

Upside down, a fish swims more efficiently at the waterline, where there’s more oxygen and better access to some prey.

—+ Read the entire article on KQED Science:

https://ww2.kqed.org/2018/04/14/the-mystery-of-the-upside-down-catfish

—+ For more information:

The California Academy of Sciences has upside-down catfish in its aquarium collection: https://www.calacademy.org/exhibits/steinhart-aquarium

—+ More Great Deep Look episodes:

Take Two Leeches and Call Me in the Morning
https://youtu.be/O-0SFWPLaII

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—+ About KQED

KQED, an NPR and PBS affiliate in San Francisco, CA, serves Northern California and beyond with a public-supported alternative to commercial TV, Radio and web media.

Funding for Deep Look is provided in part by PBS Digital Studios. Deep Look is a project of KQED Science, which is supported by the S. D. Bechtel, Jr. Foundation, the Dirk and Charlene Kabcenell Foundation, the Vadasz Family Foundation, the Gordon and Betty Moore Foundation, the Fuhs Family Foundation Fund and the members of KQED.

Take Two Leeches and Call Me in the Morning | Deep Look

(FYI – This episode is a *bit* more bloody that usual – especially a little after the 2-minute mark. Just letting you know in case flesh wounds aren’t your thing)

The same blood-sucking leeches feared by hikers and swimmers are making a comeback… in hospitals. Once used for questionable treatments, leeches now help doctors complete complex surgeries to reattach severed body parts.

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DEEP LOOK: a new ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Explore big scientific mysteries by going incredibly small.

Leeches get a bad rap—but they might not deserve it. Yes, they’re creepy crawly blood-suckers. And they can instill an almost primal sense of disgust and revulsion. Humphrey Bogart’s character in the 1951 film The African Queen even went so far as to call them “filthy little devils.”

But the humble leech is making a comeback. Contrary to the typical, derogatory definition of a human “leech,” this critter is increasingly playing a key role as a sidekick for scientists and doctors, simply by being its bloodthirsty self.

Distant cousins of the earthworm, most leech species are parasites that feed on the blood of animals and humans alike. They are often found in freshwater and navigate either by swimming or by inching themselves along, using two suckers—one at each end of their body—to anchor themselves.

Upon reaching an unsuspecting host, a leech will surreptitiously attach itself and begin to feed. It uses a triangular set of three teeth to cut in, and secretes a suite of chemicals to thin the blood and numb the skin so its presence goes undetected.

—+ Read the entire article on KQED Science: https://www.kqed.org/science/1921659/take-two-leeches-and-call-me-in-the-morning

—+ For more information:
David Weisblat at UC Berkeley studies leeches development and evolution
https://mcb.berkeley.edu/labs/weisblat/research.html

Biologists recently reported that leeches in that region can provide a valuable snapshot of which animals are present in a particular area
https://www.tandfonline.com/doi/abs/10.1080/14772000.2018.1433729?journalCode=tsab20&

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—+ See some great videos and documentaries from the PBS Digital Studios! Above the Noise:

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—+ About KQED KQED, an NPR and PBS affiliate in San Francisco, CA, serves Northern California and beyond with a public-supported alternative to commercial TV, Radio and web media.

Funding for Deep Look is provided in part by PBS Digital Studios. Deep Look is a project of KQED Science, which is supported by the S. D. Bechtel, Jr. Foundation, the Dirk and Charlene Kabcenell Foundation, the Vadasz Family Foundation, the Gordon and Betty Moore Foundation, the Fuhs Family Foundation Fund and the members of KQED.

How Ticks Dig In With a Mouth Full of Hooks | Deep Look

Why can’t you just flick a tick? Because it attaches to you with a mouth covered in hooks, while it fattens up on your blood. For days. But don’t worry – there *is* a way to pull it out.

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DEEP LOOK: a new ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Explore big scientific mysteries by going incredibly small.

Spring is here. Unfortunately for hikers and picnickers out enjoying the warmer weather, the new season is prime time for ticks, which can transmit bacteria that cause Lyme disease.

How they latch on – and stay on – is a feat of engineering that scientists have been piecing together. Once you know how a tick’s mouth works, you understand why it’s impossible to simply flick a tick.

The key to their success is a menacing mouth covered in hooks that they use to get under the surface of our skin and attach themselves for several days while they fatten up on our blood.

“Ticks have a lovely, evolved mouth part for doing exactly what they need to do, which is extended feeding,” said Kerry Padgett, supervising public health biologist at the California Department of Public Health in Richmond. “They’re not like a mosquito that can just put their mouth parts in and out nicely, like a hypodermic needle.”

Instead, a tick digs in using two sets of hooks. Each set looks like a hand with three hooked fingers. The hooks dig in and wriggle into the skin. Then these “hands” bend in unison to perform approximately half-a-dozen breaststrokes that pull skin out of the way so the tick can push in a long stubby part called the hypostome.

“It’s almost like swimming into the skin,” said Dania Richter, a biologist at the Technische Universität in Braunschweig, Germany, who has studied the mechanism closely. “By bending the hooks it’s engaging the skin. It’s pulling the skin when it retracts.”

The bottom of their long hypostome is also covered in rows of hooks that give it the look of a chainsaw. Those hooks act like mini-harpoons, anchoring the tick to us for the long haul.

“They’re teeth that are backwards facing, similar to one of those gates you would drive over but you’re not allowed to back up or else you’d puncture your tires,” said Padgett.

— How to remove a tick.
Kerry Padgett, at the California Department of Public Health, recommends grabbing the tick close to the skin using a pair of fine tweezers and simply pulling straight up.

“No twisting or jerking,” she said. “Use a smooth motion pulling up.”

Padgett warned against using other strategies.

“Don’t use Vaseline or try to burn the tick or use a cotton swab soaked in soft soap or any of these other techniques that might take a little longer or might not work at all,” she said. “You really want to remove the tick as soon as possible.”

— What happens if the mouth of a tick breaks off in your skin?
Don’t worry if the tick’s mouth parts stay behind when you pull.

“The mouth parts are not going to transmit disease to people,” said Padgett.

If the mouth stayed behind in your skin, it will eventually work its way out, sort of like a splinter does, she said. Clean the bite area with soap and water and apply antibiotic ointment.

—+ Read the entire article on KQED Science: https://www.kqed.org/science/1920972/how-ticks-dig-in-with-a-mouth-full-of-hooks

—+ For more information:
Centers for Disease Control information on Lyme disease:
https://www.cdc.gov/lyme/

Mosquito & Vector Control District for San Mateo County, California:
https://www.smcmvcd.org/ticks

—+ More Great Deep Look episodes:

How Mosquitoes Use Six Needles to Suck Your Blood
https://www.youtube.com/watch?v=rD8SmacBUcU

So … Sometimes Fireflies Eat Other Fireflies
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—+ See some great videos and documentaries from the PBS Digital Studios!

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—+ Follow KQED Science:
KQED Science: http://www.kqed.org/science
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—+ About KQED
KQED, an NPR and PBS affiliate in San Francisco, CA, serves Northern California and beyond with a public-supported alternative to commercial TV, Radio and web media.

Funding for Deep Look is provided in part by PBS Digital Studios. Deep Look is a project of KQED Science, which is supported by the S. D. Bechtel, Jr. Foundation, the Dirk and Charlene Kabcenell Foundation, the Vadasz Family Foundation, the Gordon and Betty Moore Foundation, the Fuhs Family Foundation Fund and the members of KQED.