How do fish make electricity? - Eleanor Nelsen

譯者: Ting-Yen Tsai 審譯者: Helen Chang

In 1800, the explorer Alexander von Humboldt

在西元 1800 年，探險家 亞歷山大·馮·洪保德

witnessed a swarm of electric eels leap out of the water

看見一群電鰻跳出水面

to defend themselves against oncoming horses.

來保護他們自己抵抗飛奔而來的馬

Most people thought the story so unusual that Humboldt made it up.

大多數人認為這太不尋常， 認為是洪保德編造了這個故事

But fish using electricity is more common than you might think;

但是魚產生電力這件事情， 可能比你所想的更為普遍

and yes, electric eels are a type of fish.

而且，電鰻是一種魚類

Underwater, where light is scarce,

在光源稀少的深海底下

electrical signals offer ways to communicate,

電力訊號是一種被拿來溝通

navigate,

導航、尋找

and find—plus, in rare cases, stun—prey.

和在少數情況下用來電昏獵物的方法

Nearly 350 species of fish have specialized anatomical structures

將近三百五十種的魚 體內有特殊的生理構造

that generate and detect electrical signals.

可以產生或是偵測電信號

These fish are divided into two groups,

這些魚可以根據牠們可以產生多少電力

depending on how much electricity they produce.

分為兩類

Scientists call the first group the weakly electric fish.

科學家把第一類稱為「弱電魚」

Structures near their tails called electric organs

接近牠們尾部的構造被稱作電器官

produce up to a volt of electricity, about two-thirds as much as a AA battery.

會產生一伏特的電力， 大約是一個 AA 電池的三分之二

How does this work?

怎麼辦到的呢？

The fish's brain sends a signal through its nervous system to the electric organ,

魚的大腦會透過神經系統 傳輸訊息到電器官

which is filled with stacks of hundreds

電器官被一堆有著 成千上萬個圓盤狀的

or thousands of disc-shaped cells called electrocytes.

「發電細胞」所充滿

Normally, electrocytes pump out sodium and potassium ions

通常發電細胞會送出鈉離子和鉀離子

to maintain a positive charge outside and negative charge inside.

來使外部帶正電荷、內部帶負電荷

But when the nerve signal arrives at the electrocyte,

但是當神經訊息來到發電細胞時

it prompts the ion gates to open.

它會促使離子通道被開啟

Positively charged ions flow back in.

使帶正電的離子從外面湧入細胞裡

Now, one face of the electrocyte is negatively charged outside

那麼現在，這一面的發電細胞

外面帶負電荷、裡面帶正電荷

and positively charged inside.

But the far side has the opposite charge pattern.

但是在遠端的細胞則是 有相反的帶電模式

These alternating charges can drive a current,

這些交流電能產生電流

turning the electrocyte into a biological battery.

讓發電細胞成為一個生化電池

The key to these fish's powers is that nerve signals are coordinated

魚產生電力的關鍵在於 動作協調的神經訊號

to arrive at each cell at exactly the same time.

可以在同一時間抵達每一個細胞

That makes the stacks of electrocytes act like thousands of batteries in series.

這個使得這群發電細胞 就像上千個電池串聯起來

The tiny charges from each one add up to an electrical field

各個細胞的微小電荷疊加起來

that can travel several meters.

成為可以傳遞數公尺的電力場

Cells called electroreceptors buried in the skin

而在魚的皮膚底下 被稱作「電感受器」的細胞

allow the fish to constantly sense this field

讓牠們可以隨時感受到這個電力場

and the changes to it caused by the surroundings or other fish.

和環境和其他魚所造成的電力場變化

The Peter’s elephantnose fish, for example,

例如「象鼻魚」

has an elongated chin called a schnauzenorgan

已經發展出被稱為 「Schnauzenorgan」的長下巴

that's riddled in electroreceptors.

長滿電感受器細胞

That allows it to intercept signals from other fish,

這使牠可以攔截其他魚的訊號

judge distances,

判斷距離長短

detect the shape and size of nearby objects,

偵測出附近物體的形狀和大小

and even determine whether a buried insect is dead or alive.

甚至知道被埋住的昆蟲是死是活

But the elephantnose and other weakly electric fish

但是不管是象鼻魚或是其他弱電魚

don't produce enough electricity to attack their prey.

都無法產生足以攻擊獵物的電力

That ability belongs to the strongly electric fish,

那是只有「強電魚」才具備的能力

of which there are only a handful of species.

而強電魚的種類很少

The most powerful strongly electric fish is the electric knife fish,

世界上最強大的強電魚是電刀魚

more commonly known as the electric eel.

更廣為人知的名字是「電鰻」

Three electric organs span almost its entire two-meter body.

在牠兩公尺的身軀上有著三個電器官

Like the weakly electric fish,

和弱電魚相同的是

the electric eel uses its signals to navigate and communicate,

電鰻運用電訊號來導航和溝通

but it reserves its strongest electric discharges for hunting

但是牠只在獵捕食物使用最強的電力

using a two-phased attack that susses out and then incapacitates its prey.

牠會運用兩階段的電擊， 分別來發現和電昏獵物

First, it emits two or three strong pulses,

首先，牠會發出兩次或三次的強電流

as much as 600 volts.

強度可高達六百伏特

These stimulate the prey's muscles, sending it into spasms

這會刺激獵物的肌肉並使牠們痙攣

and generating waves that reveal its hiding place.

然後產生的波動可以讓 電鰻知道獵物的藏身之處

Then, a volley of fast, high-voltage discharges

接著，在電光石火之間，高伏特的放電

causes even more intense muscle contractions.

會造成更劇烈的肌肉收縮

The electric eel can also curl up so that the electric fields

電鰻也可以蜷起身體

generated at each end of the electric organ overlap.

讓電器官兩端產生的電力場重疊起來

The electrical storm eventually exhausts and immobilizes the prey,

這次強烈的電擊最後會使獵物 筋疲力盡且失去移動能力

and the electric eel can swallow its meal alive.

此時電鰻就可以活吞獵物

The other two strongly electric fish are the electric catfish,

其他兩種強電魚是

可以發出 350 伏特的電壓的「電鯰」

which can unleash 350 volts

with an electric organ that occupies most of its torso,

牠的電器官占了牠大部分的軀幹

and the electric ray, with kidney-shaped electric organs on either side of its head

還有兩側頭部 有著腎形電器官的「電鳐」

that produce as much as 220 volts.

牠最強可以產生兩百二十伏特的電壓

There is one mystery in the world of electric fish:

現在這裡有個關於世界上 所有電魚的謎團：

why don't they electrocute themselves?

為什麼牠們在電擊時不會電到自己呢？

It may be that the size of strongly electric fish

這可能是因為強電魚的大小

allows them to withstand their own shocks,

讓牠們可以忍受自己發出的電擊

or that the current passes out of their bodies too quickly.

或是電流太快通過牠們的身體

Some scientists think that special proteins may shield the electric organs,

有些科學家認為有特殊的 蛋白質包覆住電器官

but the truth is, this is one mystery science still hasn't illuminated.

但真相是，這是一個科學 還無法解釋的謎團

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