How squids outsmart their predators - Carly Anne York

譯者: Lilian Chiu 審譯者: Helen Chang

In the ocean’s depths, two titans wage battle:

在海洋的深處，有兩巨頭在爭戰：

the sperm whale and the colossal squid.

抹香鯨和大王酸漿烏賊。

Sperm whales use echolocation to hunt these squid for food,

抹香鯨用回聲定位 來獵食這些烏賊，

but even against this gigantic animal, squid can put up an impressive fight.

但即便對手如此巨大，烏賊 也能奮勇抵抗，讓人印象深刻。

Scientists know this because on the bodies of washed-up whales,

科學家知道這一點，因為在 被沖上岸的抹香鯨的身體上，

they frequently find huge, round suction scars,

他們常常會發現大型、 圓形的吸附式傷疤，

emblazoned there by large, grasping tentacles.

十分醒目，顯然是被 很巨大的觸角緊抓過。

Ranging in size from this giant’s impressive 14 meters

這些生物的大小，從這隻 巨烏賊嚇人的 14 公尺，

to the 2.5 centimeters of the southern pygmy squid,

到南方微鰭烏賊的 2.5 公分都有，

these creatures fall into the group of animals known as cephalopods.

牠們是屬於所謂的「頭足類動物」。

There are about 500 squid species worldwide,

全世界大約有 500 種烏賊，

and they live in all the world’s oceans,

牠們住在世界上所有的海洋中，

making them a reliable food source for whales,

這點讓牠們成為可靠的 食物來源，被鯨魚、

dolphins,

海豚、

sharks,

鯊魚、

seabirds,

fish,

海鳥、

魚類，

and even other squid.

甚至其他烏賊所獵食。

Indeed, squid themselves are fearsome ocean predators.

的確，烏賊本身就是讓人 害怕的海洋捕食性動物。

But their most extraordinary adaptations

但牠們最不凡的適應能力，

are those that have evolved to help them thwart their predators.

是進化之後能夠協助牠們 阻撓其他捕食者的能力。

Squid, which can be found mainly

能夠找到烏賊最主要的地方，

in estuarine, deep-sea, and open-water habitats,

包括入海口、深海， 以及開放水域棲息地，

often swim together in shoals.

牠們通常會成群而行。

Being out in the open without anywhere to hide makes them vulnerable,

在無處可躲的開放空間中， 牠們是很脆弱的，

so as a first line of defense, they rely on large, well-developed eyes.

所以，牠們的第一線防禦， 是發展良好的大眼睛。

In the colossal squid, these are the size of dinner plates,

大王酸漿烏賊的眼睛 就和晚餐餐盤一樣大，

the largest known eyes in the animal kingdom.

就我們所知，是動物 王國中最大的眼睛。

When it’s dark or the water is murky, however,

然而，天色暗時或在昏暗的水中，

squid rely on a secondary sensory system,

烏賊要依靠的是第二感覺系統，

made from thousands of tiny hair cells that are only about twelve microns long

它是由數千個微小毛細胞所組成， 這種細胞只有大約 12 微米長，

and run along their heads and arms.

滿佈在牠們的頭部和手臂上。

Each of these hair cells is attached to axons in the nervous system.

每一個毛細胞都連結到 神經系統的軸索。

Swimming animals create a wake,

游泳型的動物會造成尾波，

so when the hairs on the squid’s body detect this motion,

所以，當烏賊身體上的毛 偵測到這運動，

they send a signal to the brain,

就會發送一個訊號給大腦，

which helps it determine the direction of the water’s flow.

來協助它判定水流的方向。

This way, a squid can sense an oncoming predator in even the dimmest waters.

這麼一來，烏賊就能在 最暗的水中感受到捕食者來襲。

Aware of the threat, a squid can then mask itself from a predator.

察覺到有威脅之後， 烏賊就能以偽裝來躲避捕食者。

Squid skin contains thousands of tiny organs called chromatophores,

烏賊皮膚含有數千個 微小的器官，叫做色素體，

each made of black, brown, red or yellow pigments and ringed in muscle.

每個都是由黑色、褐色、紅色， 或黃色色素所構成，被肌肉包覆。

Reflecting cells beneath the chromatophores

在色素體底下的反射細胞

mirror the squid’s surroundings, enabling it to blend in.

會反映出烏賊的周圍環境， 讓牠融入其中。

So, when the muscles contract,

所以，當肌肉收縮時，

the color of the pigment is exposed,

色素的顏色就會暴露出來，

whereas when the muscles relax the colors are hidden.

肌肉放鬆時，顏色則會隱藏。

Each of these chromatophores

每一個色素體

is under the individual control of the squid’s nervous system,

都受到烏賊神經系統的個別控制，

so while some expand, others remain contracted.

所以可以做到有些放鬆，有些收縮。

That enables countershading,

那就能做到反蔭蔽，

where the underside of the squid is lighter than the top,

讓烏賊的底面顏色比上面更淡，

to eliminate a silhouette that a predator might spy from below.

讓捕食者無法從下方看到輪廓。

Some predators, however, like the whales and dolphins,

然而有些捕食者，像是鯨魚和海豚，

get around this ruse by using sound waves to detect a squid’s camouflaged form.

能對付這種花招，牠們會用 聲波來偵測烏賊的偽裝形式。

Not to be outfoxed, the squid still has two more tricks up its sleeve.

烏賊也不甘勢弱， 還有兩項絕招可以搬出來。

The first involves ink, produced inside its mantle.

第一項和牠的套膜內部 產生出的墨汁有關。

Squid ink is made mostly of mucus and melanin,

烏賊墨汁主要的成份 是黏液和黑色素，

which produces its dark coloring.

黑色素是墨汁顏色這麼深的原因。

When squid eject the ink,

當烏賊噴出墨汁時，

they either use it to make a large smokescreen

牠們可以用墨汁製造大型煙幕效果，

that completely blocks the predator’s view

讓捕食者完全看不見，

or a blob that roughly mimics the size and shape of the squid.

也可以用一團墨汁大致 仿造出烏賊的大小和形狀。

This creates a phantom form, called a pseudomorph,

這會創造出一幽靈形，稱為偽形，

that tricks the predator into thinking it’s the real squid.

欺騙捕食者，讓牠誤認 那就是真正的烏賊。

As a final touch, squid rely on jet propulsion

最後還有神來一筆， 烏賊還能仰賴噴射推進，

to rapidly shoot away from their hunters,

快速逃離牠們的捕食者，

reaching speeds of up to 25 miles per hour and moving meters away in mere seconds.

速度可高達每小時 25 英哩， 只要幾秒鐘就可移動數公尺。

This makes them Earth’s fastest invertebrates.

這點讓牠們成為地球上 最快速的無脊椎動物。

Some squid species have also developed unique adaptive behaviors.

有些種類的烏賊也發展出 獨特的適應行為。

The deep-sea vampire squid, when startled,

深海的吸血烏賊在受到驚嚇的時候

uses its webbed arms to make a cape it hides behind.

會用牠蜘蛛網狀的手臂 做出一個斗篷，躲在後面。

The tiny bobtail, on the other hand, tosses sand over its body

另一方面，小短尾則可以 把沙子拋上牠的身體，

as it burrows away from prying eyes.

讓它能躲起來不被 刺探的眼睛給發現。

The Pacific flying squid uses jet propulsion for another purpose:

鯣烏賊會把噴射推進 拿來做另一個用途：

to launch itself right out of the water.

把自己射出水面。

Squids’ inventive adaptations have allowed them

烏賊很有創造力的適應力，

to proliferate for over 500 million years.

讓牠們能夠持續增生超過五億年。

Even now, we’re still uncovering new species.

即使現在，我們還在發掘新品種。

And as we do,

當我們發現更多品種時，

we’re bound to discover even more about how these stealthy cephalopods

我們也就能更了解這些 鬼鬼祟祟的頭足類動物

have mastered survival in the deep and unforgiving sea.

是如何在又深又無情的海洋中 精通生存技巧。