Which animal has the best eyesight? - Thomas W. Cronin

譯者: Camila Lin 審譯者: Yi-Ping Cho (Marssi)

The animal kingdom boasts an incredible diversity of eyes.

動物王國裡的動物 有許多不同種類的眼睛。

Some rotate independently, while others have squiggly-shaped pupils.

有些眼睛可以個別旋轉， 有些眼睛有波浪狀的瞳孔。

Some have protective lids, others squirt blood.

有些眼睛具有保護性的眼皮， 有些眼睛則會噴血。

But which creature has the best sight?

但哪種生物的視力最好？

Which sees best in the darkness?

在黑暗中誰看得最清楚？

Which sees the most detail?

誰能看得最詳細？

Which animal sees the most color?

誰能看到最多種顏色？

And finally, which detects motion the fastest?

最後，誰又能最快偵測到動靜？

All eyes take in sensory stimuli in the form of waves of light.

所有眼睛都以光波形式接收感官刺激。

To convert these into everything we see,

為了將這些光波轉化 為我們看見的一切，

eyes focus incoming light onto photoreceptors.

眼睛會將入射光聚焦到感光體上。

These cells translate light into neural signals

這些感光細胞會將光波轉為神經訊息，

and send them to the brain, where they’re finally processed.

傳送給大腦處理。

The eyes that see best in darkness are those that capture

夜視能力最強的眼睛

就是那些能盡量吸收光線的眼睛。

as much available light as possible.

Colossal squids have soccer-ball-sized eyes—

大王酸漿魷的眼睛有一粒足球那麼大，

the largest known in existence.

是目前已知最大的眼睛。

These may help them spot the faint glow of sperm whales

牠們的大眼似乎有助於捕捉 抹香鯨干擾身邊發光生物時

as they disturb light-producing organisms.

所閃爍的微弱燈光。

Some fish have eyes that are unique among vertebrates because they use mirrors.

在脊椎動物中，某些魚的眼睛 也十分獨特，因為它們會使用鏡子。

For the brownsnout spookfish,

對四眼魚來說，

each eye has an upward-facing lens and a downward-pointing mirror

兩眼都有一片朝上的晶體， 和一面朝下的小鏡子，

composed of tiny crystal plates that efficiently gather light.

組成小小的透明圓盤，有效吸收光線。

They can see up and down simultaneously,

牠們能夠同時看見上下，

and may perceive distinct shapes, even in the ocean’s depths.

就算在海洋深處， 也能辨認出不同的形狀。

Back on solid ground, arctic reindeer have adaptations

回到陸地，北極馴鹿演化出

to deal with months of darkness.

能夠應付長達數月黑暗的眼睛。

The backs of reindeer eyes change color, from gold in summer to blue in winter.

馴鹿的眼睛後方會隨季節改變顏色， 夏天是金色，冬天是藍色。

Their blue-backed eyes are about 1,000 times more sensitive to light.

藍眼對光的敏感度 比金眼高出大約一千倍。

This may allow reindeer to recognize important things in the snow

這讓馴鹿能在雪中發現重要的東西，

like urine and lichen.

像是尿液或是地衣。

When it comes to the sharpest vision, birds of prey soar above the competition.

說到最銳利的視線， 猛禽將其他動物狠甩千里。

To capture the most detail, an animal must have lots of photoreceptors in its eye,

為了捕捉最細微的線索， 動物的眼睛必須具備許多感光體，

as well as increased visual processing power.

也必須提高視覺處理的速度。

Raptors have an especially deep fovea—

猛禽的「中央窩」特別深邃，

a depression in the back of their eye that fits more photoreceptors.

牠們眼窩的凹陷能容納更多感光體，

So, Peregrine falcons have vision that’s more than twice as sharp as a human’s.

所以，遊隼的視力 比人類還強兩倍以上，

They’re able to zero in on a rabbit from more than three kilometers away.

牠們能在三公里外就能鎖定兔子。

When crowning the creature with the best color vision,

但說到能分辨出最多種顏色的冠軍，

the picture gets complicated.

情況就變得有些複雜。

Different photoreceptors are sensitive to specific waves of light,

不同的感光體偵測不同的光波，

meaning the colors we see are largely determined

表示我們能看到的顏色，

大多取決於我們擁有哪種感光體。

by what kinds of photoreceptors we have.

Presumably, the more types of color photoreceptors an animal has,

可以說，具備越多種感光體，

the better its color vision.

色覺就會越好。

Dogs have just two types.

狗只有兩種感光體。

Humans have three.

人則有三種。

And we are far outdone by some birds, fishes, and insects.

許多鳥類、魚類及昆蟲 把我們遠遠甩在後頭。

Bluebottle butterflies have at least 15 types of photoreceptors.

青鳳蝶至少具有十五種感光體。

Seven of them are attuned to distinct blues and greens,

其中七種能敏銳分辨藍色與綠色，

which researchers think might help them track each other during high-speed chases.

研究者認為，這可能有助於牠們 以高速追逐彼此時仍能鎖定對方。

Mantis shrimp have a whopping 16 kinds of photoreceptors,

蝦蛄有十六種感光體，

with five reserved just for the ultraviolet, or UV, spectrum,

其中五種專門用來偵測 人類看不見的紫外線光譜。

which humans can’t see.

But experiments suggest that the mantis shrimp’s ability

但實驗認為蝦蛄分辨顏色的能力

to discriminate between colors is more limited than you might expect.

遠低於我們的想像。

Exactly how they use their complex eyes is a mystery.

我們仍不清楚牠們如何 運用如此複雜的眼睛。

Meanwhile, with just four kinds of color photoreceptors,

現在，只有四種感光體的金魚，

goldfish actually excel at discerning subtle differences in shades.

其實特別擅長分別細微的色調差異。

Finally, insects have mastered the ability to see the world... on the fly.

最後，昆蟲掌握了看清世界的能力， 但僅限於飛行期間。

The fastest motion vision requires photoreceptors

最快的動態視力需要

能快速感知光影變化的感光體，

that quickly sense changes in light,

and a brain that rapidly processes the information.

以及能快速處理訊息的大腦。

A movie shot at 24 frames per second gives us the perception

每秒二十四幀的電影在我們看來

of near seamless motion.

就像連貫的動作，

But insects would see a slideshow.

但昆蟲看見的卻是一張張的投影片。

Fly photoreceptors register changes 10 times faster than we do,

蒼蠅感光體的處理速度比我們快十倍，

making them especially hard to catch.

因此牠們特別難被捕捉。

These animals have some of the best vision we know of,

這些動物擁有我們已知最棒的視力，

but there's no winner across the board.

但沒有贏家能夠面面俱到。

Each category has different top contenders because vision requires tradeoffs.

每一類視力都有不同冠軍， 是因為視力需要取捨。

So, some eyes are highly specialized,

所以，有些眼睛特別專精在某一方面，

while others, like ours, perform decently in many categories.

有些眼睛則跟人類的眼睛一樣， 在各類別都達到平均水準。

From eyes the size of soccer balls to those that see in UV—

從足球般大的眼睛 到可以看見紫外線的眼睛，

the ways of looking at the world are as varied as the life forms in it.

看世界的方式，就像生命一樣多元。