Name: あなたが聞いたこともないような信じられないようなタコ。ブランケットタコ (The Most Incredible Octopus You’ve Never Heard of: The Blanket Octopus)
Uploaded: 2021-01-14T10:53:14.000Z
Duration: 5 min 14 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

All octopuses start out as teeny, tiny plankton,

drifting through the ocean at the mercy of currents.

Eventually, though, they get big enough to settle down

and make a home for themselves on the seafloor...

The four species in the genus Tremoctopus never settle down.

Though they get quite big, they spend their lives

And not even scientists know very much about these nomadic invertebrates.

It turns out they have some pretty weird traits

including those blanket-like appendages they're named after.

Most octopuses spend a lot of their lives hiding,

whether it's in rocky dens, holes in the sand, or large shells.

They only swim around when hunting or defending their territory

—and even then, they'd prefer to crawl.

Which I guess makes sense, since they have no bones

The only hard part of an octopus is its beak

—the calcified mouthparts it uses to eat its prey.

And blanket octopuses are also mostly soft.

But still, they don't seek protection on the seafloor.

They are generally found cruising through warm, tropical waters

And they can do that because they have all the usual

octopus defenses—like the ability to release ink

There's that namesake blanket, for instance.

It refers to the long transparent webs of skin

When threatened, she is able to unfurl all this skin

and trail it out behind her like a superhero's cape.

And in the largest species, she can grow to be over 2 meters long.

So when you combine her size with her incredible cape,

If this doesn't scare off a would-be predator,

she may be able to ditch the blanket instead.

Lone blankets have been spotted by divers, and some experts

believe that's because a female can break it off

much like a lizard does its tail when threatened.

The idea being that, hopefully, that distracts the predator

long enough for her more essential bits to escape.

They're actually immune to the stinging cells

of Portuguese man o' war and their close relatives.

A young female blanket octopus will swim up to a man o' war,

rip off its tentacles, and then carry them around using her suckers.

Then, when a threat comes too close, she can wield them

It's something the unfortunate scientist who first published

Now the males steal tentacles to defend themselves, too.

But they don't just wield them when they're young because… well…

In fact, they're so tiny that scientists didn't observe them

The males of the largest species only grow to be about

On average, males are one one-hundredth the length

and 40 thousand times less massive than their mates!

That's the most extreme size difference between sexes

that we know of among non-microscopic animals.

Just imagine if your spouse were the size of a walnut.

Scientists think that the males evolved to be so small

because all they really need to do is mate.

You see, all male octopus have a special appendage

called a hectocotylus—what is sometimes totally seriously referred to

as a “sex arm”—that they can fill with packets of sperm.

In most other species, a male sticks this sex arm

into a female's mantle cavity during courtship

to deposit his sperm packets—a process that can take several hours.

But in the open ocean, there's zero privacy,

When a male and female blanket octopus meet,

he just rips off his sex arm and quickly sneaks it into her.

The arm crawls on its own up deeper into the female

—where it might find a few other arms already hanging out.

Eventually, the female will run out of space.

So for males, it's not size that matters—it's speed.

And growing big takes time, so larger males are at a disadvantage.

Once a male has delivered his sex arm, he dies.

Then, when the female is ready, she picks the arm she likes best

and squeezes the sperm all over her eggs.

If she lived on the bottom like other octopus, she'd probably

lay these eggs in her den so she could care for them until they hatch.

But, since the open ocean lacks adequate housing, she constructs

a cigar-shaped anchor rod for them out of calcium carbonate

—the same stuff in shells and coral skeletons.

And around 100 thousand eggs can attach to this rod,

which hangs on one of her arms, keeping them all safe

while she continues to move about the ocean.

It's thought that she dies shortly after the babies hatch,

mostly because that's what other female octopus do

In fact, we have a lot left to learn about blanket octopus,

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あなたが聞いたこともないような信じられないようなタコ。ブランケットタコ (The Most Incredible Octopus You’ve Never Heard of: The Blanket Octopus)

eventually

incredible

evolve

bizarre