Why do we harvest horseshoe crab blood? - Elizabeth Cox

譯者: Sherl H 審譯者: Helen Chang

During the warmer months, especially at night during the full moon,

在較暖和的月份裡 尤其是滿月的夜晚

horseshoe crabs emerge from the sea to spawn.

馬蹄蟹浮出海水來產卵

Waiting for them are teams of lab workers

等待著牠們的是實驗室工作團隊

who capture the horseshoe crabs by the hundreds of thousands,

他們捕捉數十萬隻馬蹄蟹

take them to labs,

帶牠們到實驗室

harvest their cerulean blood,

採集牠們蔚藍的血液

then return them to the sea.

再將牠們放回大海

Oddly enough, we capture horseshoe crabs on the beach

說來奇怪 我們在海灘上捕捉馬蹄蟹

because that's the only place we know we can find them.

因為那是我們唯一所知 能找到牠們的地點

A female horseshoe crab lays as many as 20 batches of up to 4,000 eggs

一隻雌馬蹄蟹每年可在海灘

產下多達 20 批 最多 4000 顆卵

on her annual visit to the beach.

When the eggs hatch,

當卵孵化

the juvenile horseshoe crabs often stay near shore,

幼馬蹄蟹常待在岸邊

periodically shedding their shells as they grow.

隨著成長 週期性地脫殼

Once they leave these shallow waters,

一旦牠們離開這些淺水區

they don't return until they reach sexual maturity ten years later.

直到十年後性成熟時才回來

Despite our best efforts, we don't know where they spend those years.

即使竭盡所能 我們還是不知道 牠們在哪裡度過年輕的歲月

Though we've spotted the occasional horseshoe crab

雖然我們曾目擊偶然出現的馬蹄蟹

as deep as 200 meters below the ocean's surface,

在海面下 200 公尺深處

we only see large groups of adults when they come ashore to spawn.

我們只會在牠們來岸邊產卵時 看到大群的成年馬蹄蟹

Horseshoe crab blood contains cells called amebocytes

馬蹄蟹的血含有一種 稱為「變形細胞」的細胞

that protect them from infection by viruses,

會保護牠們不受病毒

fungi,

真菌

and bacteria.

和細菌的感染

Amebocytes form gels around these invaders

變形細胞會在這些入侵者周圍形成凝膠

to prevent them from spreading infections.

以防止它們擴大感染

This isn't unusual.

這並不稀奇

All animals have protective immune systems.

所有動物都有防禦用的免疫系統

But horseshoe crab amebocytes are exceptionally sensitive

但馬蹄蟹的變形細胞

對於細菌的「內毒素」異常地敏感

to bacterial endotoxins.

Endotoxins are molecules from the cell walls of certain bacteria,

內毒素來自某些細菌細胞壁的分子

including E. coli.

包括大腸桿菌

Large amounts of them are released when bacterial cells die,

當細菌死亡時 大量內毒素被釋出

and they can make us sick if they enter the blood stream.

如果它們進入血液 可能使我們生病

許多我們所仰賴的藥物和醫療器械 都可能受汙染

Many of the medicines and medical devices we rely on can become contaminated,

so we have to test them before they touch our blood.

所以我們需要 在它們接觸到血液前先測試

We do have tests called Gram stains that detect bacteria,

我們確實有叫做 「革蘭氏染色」的檢驗能偵測細菌

but they can't recognize endotoxins

但它們無法認出內毒素

which can be there even when bacteria aren't present.

即使不存在細菌 也可能有內毒素在那兒

So scientists use an extract called LAL

所以科學家使用 一種叫做 LAL 的萃取物

produced from harvested horseshoe crab blood

由抽取出的馬蹄蟹血液製成

to test for endotoxins.

來檢測內毒素

They add LAL to a medicine sample, and if gels form,

他們將 LAL 加入藥物樣品 假如形成膠狀

bacterial endotoxins are present.

表示細菌內毒素存在

Today, the LAL test is used so widely

現今 LAL 測試使用廣泛

that millions of people who've never seen a horseshoe crab

數百萬未曾見過馬蹄蟹的人們

have been protected by their blood.

曾被牠們的血守護

If you've ever had an injection, that probably includes you.

如果你曾經打過針 你可能也包括在內

How did horseshoe crabs end up with such special blood?

究竟馬蹄蟹怎麼會有 如此特別的血液呢

Like other invertebrates,

如同其他無脊椎動物

the horseshoe crab has an open circulatory system.

馬蹄蟹有開放式循環系統

This means their blood isn't contained in blood vessels, like ours.

意思是牠們的血不像我們的 是裝在血管裡的

Instead, horseshoe crab blood flows freely through the body cavity

馬蹄蟹的血卻在體腔內自由流動

and comes in direct contact with tissues.

並且直接與身體組織接觸

If bacteria enters their blood, it can quickly spread over a large area.

如果細菌進入牠們的血液 便能迅速擴散到大片區域

Pair this vulnerability

將這個弱點

with the horseshoe crab's bacteria-filled ocean and shoreline habitats,

與馬蹄蟹充滿細菌的海洋 及海濱棲地配對起來

and it's easy to see why they need such a sensitive immune response.

就很容易看出為什麼牠們需要 這麼敏感的免疫反應了

Horseshoe crabs survived mass extinction events

馬蹄蟹在消滅了地球上 90% 的生物

that wiped out over 90% of life on Earth and killed off the dinosaurs,

並殺盡恐龍的大滅絕事件中 存活了下來

but they're not invincible.

但牠們並非無敵

And the biggest disruptions they've faced in millions of years come from us.

數百萬年來 牠們面臨最大的瓦解危機

來自於我們

Studies have shown that up to 15% of horseshoe crabs

研究顯示 高達 15% 的馬蹄蟹

die in the process of having their blood harvested.

在血液採集的過程中死亡

And recent research suggests this number may be even higher.

而最近的研究表示 這個數字甚至可能還更高

Researchers have also observed fewer females returning to spawn

研究者也發現 在某些捕獲馬蹄蟹最多的地區

at some of the most harvested areas.

回來產卵的雌馬蹄蟹變少了

Our impact on horseshoe crabs extends beyond the biomedical industry, too.

我們對馬蹄蟹的影響 也延伸到生醫產業之外

Coastal development destroys spawning sites,

海濱發展破壞了產卵地點

and horseshoe crabs are also killed for fishing bait.

馬蹄蟹也被殺來做魚餌

There's ample evidence that their populations are shrinking.

有充分證據顯示牠們的族群正在縮小

Some researchers have started working

有些研究者已經開始動工

to synthesize horseshoe crab blood in the lab.

在實驗室中合成馬蹄蟹的血液

For now, we're unlikely to stop our beach trips,

目前我們不太可能 不去海灘收集馬蹄蟹

but hopefully, a synthetic alternative will someday eliminate our reliance

但希望有一天 合成替代品會終結

我們對於這些古老生物血液的依賴

on the blood of these ancient creatures.