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Michael Aranda shares some newly discovered animal oddities this week, including the secret shared by sloths and moths, the largest animal genome ever sequenced, and unusual new life at the bottom of the world.
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Michael Aranda: If you are a person, you probably had to get out of bed today so you could go to work and get some food. But imagine being able to grow all of the food you’ll ever need on your own body, so the only reason you ever need to get up is to poop. Well, you wouldn’t have to imagine it if you were a three-toed sloth.

From the lazy world of sloths to the upside-down world of Antarctic sea anemones, we made some weird animal discoveries this week. I’m Michael Aranda standing in for Hank Green and you’re watching SciShow News.


On Wednesday, biologists from the University of Wisconsin explained how the famous laziness of sloths allows them to nourish a whole ecosystem, starting with their poop. It’s kind of hard to get enough nutrients when you live in a tree, so sloths spend as little energy as possible. The two-toed species roam slowly from tree to tree, pooping wherever they happen to be when the urge hits, but the three-toed species only move about once per week, and that’s to perform their weekly toilet ritual.

The sloth descends from its tree, digs a hole, poops in it, covers it with leaves, and then ascends again. The researchers were curious about this behavior, so they took a closer look at the ecology on the animals themselves. Turns out, sloth hairs are full of cracks that absorb water and promote the growth of algae, which is full of fat and nutrients, a handy source of food for the sloths.

Because who doesn’t love to eat the stuff that grows in your hair cracks?

In addition to the algae within the sloth’s fur, there are also all kinds of arthropods, including the phoretic moth. These moths live in the sloth’s fur, but they lay their eggs in the dung it leaves on the ground. When hatched, the mothlings then fly up to the nearest sloth to live out their short moth lives until they die and their decomposing bodies add nutrients to the sloth-fur jungle.

In a study of 33 sloths from Costa Rica, researchers counted the number of moths on each and measured the concentration of nitrogen and algae on them. It turned out that the three-toed sloths had about five times as many moths on them, twice as much nitrogen and one-third more algae than the two-toed sloths. It appears their special pooping method creates a great egg-laying habitat for moths which then add their bodies’ nitrogen to the fur when they die and fuel more delicious algae growth. It’s the perfect example of mutualism: a mutually-beneficial relationship between two organisms. It might be that this weekly poop habit helps the three-toed sloth to live its slothful life.

If only locusts were as lazy.

The notorious flying grasshopper eats its own body weight every day, and when it gets into its so-called ‘gregarious’ phase, it forms enormous swarms that destroy whole crops. Last week, geneticists from the Institute of Zoology and the Chinese Academy of Sciences said they had sequenced the entire genome of one of the worst of these offenders, Locusta migratoria, the migratory locust found in Africa, Asia and Australia, in hopes of finding some ways to keep the insects at bay. And they were shocked when the locust turned out to have the largest animal genome ever sequenced, filling up some 6.5 gigabytes of data.

The human genome, by comparison, is only 3.2 gigabytes.

It appears that locusts have large clusters of genes that are responsible for their ability to find and digest food, fly long distances and swarm. Pin-pointing some of these genes could be the next step in developing smart pesticides to combat the locusts and help defend food supplies the world over.

Finally, credit for the third animal oddity goes to geologists from the University of Nebraska who discovered an ecosystem deep under the ice of Antarctica. Hoping to survey tides under the Ross Ice Shelf, they drilled a hole through the 270-meter thick ice, sent in a camera-equipped robot, flipped it upside down and were totally floored to see the bustling ecosystem attached to the bottom of the ice. Thousands of tiny sea anemones dangled from the ice, and fish, worms and other creatures swam upside-down among them.

The white one-inch anemone is the first such animal known to live in ice and upside-down.

Because they weren’t prepared for such a discovery, the researchers came away with little more than photographs and a few preserved specimens. But it’s clear that this is a new species, and there’s much more to learn about how they feed, produce and burrow in the hard ice. Further studies may provide insight into how life could exist in extreme environments on other worlds, such as the freezing oceans of Europa.

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