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Duration:05:01
Uploaded:2016-12-29
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We’re pretty good at moving around in the world, but there are some animals that have efficient mechanisms that allow them to leap and bound wherever they go. Gears, bows, and springs allow these animals to be amazing jumpers.

Hosted by: Olivia Gordon
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Sources:
Kangaroo “springs”
http://animals.howstuffworks.com/mammals/kangaroo-hopping1.htm
http://www.discoverwildlife.com/animals/mammals/how-and-why-do-kangaroos-hop
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.1975.tb05983.x/abstract

Locust “bows”
http://www.ncbi.nlm.nih.gov/pubmed/22693029
https://www.st-andrews.ac.uk/~wjh/jumping/legsprng.htm

Planthopper “gears”
http://science.sciencemag.org/content/341/6151/1254
http://www.sciencedirect.com/science/article/pii/S1095643309004012
http://www.nature.com/news/insect-leg-cogs-a-first-in-animal-kingdom-1.13723
https://www.youtube.com/watch?v=xQk-lP2R04Y

Images:
Kangaroo: https://commons.wikimedia.org/wiki/File:Unidentified_kangaroo_-Blue_Mountains,_New_South_Wales,_Australia-8.jpg
Juvenile Planthopper Nymph: https://commons.wikimedia.org/wiki/File:Nymph_of_Issus_coleoptratus_planthopper.jpg
Planthopper Nymph: https://commons.wikimedia.org/wiki/File:Issus_coleoptratus_(Planthopper_sp.)_nymph,_Arnhem,_the_Netherlands.JPG
Olivia" There are some athletes with awesome jumping abilities, flinging their bodies to human extremes in the high jump or the long jump. Others combine strength and endurance, like basketball or volleyball players, who leap up to slam dunk or spike. But, when it comes to endurance, speed, and strength, some animals are leaps and bounds ahead of us, using their bodies like springs, bows, or gears to power them onwards and upwards.

We all know that kangaroos jump. It’s kind of their thing, besides cute joeys in pouches and sometimes weirdly beefy pecs. They jump instead of run, and they can keep it up for hours and hours in the vast outback, where food and water sources might be hundreds of kilometers apart.

Traveling long distances can be challenging, and they don’t have the luxury of protein bars and sports drinks for energy boosts. Not to mention the fatigue if they relied on muscle-power alone. So, instead, they’re using their legs like energy-efficient springs.

See, kangaroos are marsupials, which are close cousins of mammals like us. Our legs have similar tissues and structures, like tendons at the base of the ankle which connects muscle to bone. But these tendons also have a key difference: in humans, they’re strong, but fairly taut. But in kangaroos, they’re built to stretch. Like biological pogo-sticks, the tendons absorb energy as a kangaroo lands, and then releases it again for the next leap.

That way, their muscles are still involved in jumping, but they're doing way less work. And this hopping system is really efficient. Unlike humans, who work our leg muscles harder the faster we run, a kangaroo’s muscles do the same amount of work over a whole range of jumps. They just have to change the angle of take-off to tweak how fast and far they leap. This efficiency means they have a lot of endurance, bounding across long distances at an Olympic sprinter’s pace, just to find their next meal.

Rather than endurance, locusts have evolved explosive, speedy jumps. They can take off in just 30 milliseconds – many times faster than the blink of an eye. This makes them pretty tricky to catch if you’re a predator. Like the kangaroo, their jump is all about energy storage and release. But kangaroo legs work more like springs, while locust legs work more like bows.

Bows amplify power: As you pull a bowstring back, it stores energy from your upper body muscles, and lets you unleash it all at once to shoot a speedy arrow. Your muscles don’t get faster or stronger just by picking up a bow. It’s a tool that changes how the energy is stored and transferred.

Now, the locust’s bow is in its knee, a kind of bow-shaped region called the semi-lunar process. At the first sign of a threat, the locust steadily contracts its large thigh muscles, storing tension in the semi-lunar process. If things get really scary, it releases that tension – firing a muscle mechanism in its own hind legs, and catapulting away from danger!

Some of the most lightweight, high-power, and long-lasting bows are composite bows, which combine properties of two different materials, like wood and horn. Same goes for locust knees. The semi-lunar process is made from a stiff cuticle plus a rubbery layer of a protein called resilin that bounces back into shape after a jump. This lets the locust jump over and over again without wearing its knees out, and live to leap another day.

Planthopper nymphs are unassuming little critters, just a few millimeters long. But at least one species is hiding a biological marvel that researchers just discovered in 2013: functional, interlocking gears that connect their back legs.

This kind of mechanical connection has never been seen in animals before, and helps the planthopper nymph control its high-speed jumps. While locusts push off from their knees, kicking straight back, planthoppers power their jumps by rotational forces in their hips. Their thighs rotate outward, pushing sharply to the ground--Like frogs, but on a teeny tiny scale!

If a planthopper’s back legs fire in sync, it makes for a powerful, balanced leap. But if one leg’s timing is even a tiny bit off, the nymph spins out and could land anywhere – like right into a predator’s mouth. It only takes a planthopper two milliseconds to blast off, which is faster than locusts! At that speed, even electric nerve signals might have trouble coordinating the two hind legs.

To solve this problem, the planthopper nymphs have physically connected hind legs, thanks to gears made out of a tough cuticle, with rows of tiny teeth that interlock. This way, when one leg moves, the other one will too – within 30 microseconds! Each jump can make the difference between being alive or being dinner, so these thigh-gears help planthoppers leap away from danger, rather than tumbling back into it.

So whether it’s an endurance test to find food, or a quick getaway to avoid becoming food, there are some amazing animals that keep on moving – with a hop, skip and a jump.

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