How do oysters make pearls? - Rob Ulrich

Translator: EMILY JIA HUEI Lim Reviewer: Aubrey Cheng

While most people wouldn’t consider the crusty exterior of an oyster

大多數人都唔覺得粗糙嘅蠔殼

to be particularly beautiful,

特別靚

opening up this craggy case might reveal an exquisite jewel nestled within.

一打開岩巉硬殼就會發現

裏面有粒精美嘅珍珠

Yet, despite their iridescent colors and smooth shapes,

雖然佢哋色彩斑斕、形狀光滑

pearls are actually made of the exact same material

珍珠嘅原料其實同保護

as the shell that surrounds them.

佢自己嘅外殼係一樣

Pearls, urchin spines, the shells of mussels, snails and clams, even coral—

珍珠、海膽刺、青口、蝸牛同蜆嘅殼， 甚至珊瑚

all these structures are made out of the same chemical compound:

佢哋嘅結構都由相同嘅化合物組成

calcium carbonate.

就係：碳酸鈣

So, how does this single ingredient form such a vast array of materials?

得一種成分點做出噉多樣物料

Calcium carbonate, or CaCO3, is common on land,

碳酸鈣CaCO3喺陸地上非常普遍

and even more bountiful in the sea.

喺海入面甚至仲豐富

The Earth’s crust is rich in calcium,

地殼含有豐富嘅鈣質

and over millennia these deposits have seeped into rivers and oceans.

幾千年嚟呢啲礦物已經渗入咗河流同海洋

This is especially true near hydrothermal vents,

特別係喺海底熱泉附近

where hot seawater mingles with calcium rich basalts.

熱海水混合埋含豐富鈣質嘅玄武岩

Meanwhile, when carbon dioxide in the air interacts with seawater

同時，空氣中二氧化碳同海水互相影響

it eventually produces dissolved carbonate.

會產生溶解嘅碳酸鹽

Every year, the ocean absorbs roughly one third of our carbon dioxide emissions,

每年， 海洋吸收大約 三分之一嘅二氧化碳排放量

adding huge quantities of carbonate into the water.

喺水入面大量增加碳酸鹽

It’s no surprise that sea creatures have made use of these abundant compounds,

海洋生物利用呢啲豐富嘅化合物都好合理

but the way calcium and carbonate are woven together into various shapes

但鈣同碳酸鹽交織而成各種形狀嘅方式

is surprisingly artful.

非常巧妙

Let’s return to the humble oyster.

我哋講返平平無奇嘅蠔

Like many aquatic mollusks, oysters start life as exposed larvae,

就好似好多水生軟體動物噉， 蠔本身係幼蟲嚟

and quickly get to work building a protective shell.

佢哋快快手建構保護殼

First, an organ called the mantle secretes an organic matrix

首先，外套膜呢個器官會分泌含蛋白質嘅

of proteins and other molecules to construct a scaffold.

有機基質同其他分子建構支架

Then, the oyster filters the seawater,

然後，蠔就會過濾海水

drawing out calcium and carbonate to combine them into its building material.

提取鈣同碳酸鹽，結合到建築材料之中

It lays this material over the scaffold,

佢將材料放喺

which is covered in charged proteins that attract and guide

冚喺帶電蛋白質嘅支架上面去引

the calcium carbonate molecules into layers.

碳酸鈣分子成為一層層嘅塗層

The specific arrangement of these protein scaffolds depends on the mollusk species

呢啲蛋白質支架嘅具体排列 取决於軟體動物嘅種類

and their environment,

同環境

accounting for their vast diversity of shell shapes, sizes, and colors.

解釋咗種類繁多嘅貝殼形狀、大細、顏色

Mollusks carefully control all components of their calcium carbonate creations—

軟體動物小心控制 佢哋產生嘅碳酸鈣嘅所有成分

even manipulating CaCO3 at the molecular level.

甚至喺分子水平上操縱 CaCO3

Using special proteins,

運用特别嘅蛋白質

mollusks can produce two crystal structures out of CaCO3:

軟體動物製造到CaCO3 嘅兩種晶體結構：

calcite and aragonite.

方解石同霰石

Both of these compounds have the same chemical composition,

呢兩種化合物都有相同化學成分

but different qualities due to the way their crystal lattices are arranged.

但因晶格排列方式唔同，質量都唔同

Calcite is the more stable of the two and less prone to dissolving over time,

方解石係兩者中較穩定， 唔太受時間影響而溶解

so most mollusk shells have a sturdy outer layer of calcite.

大多數軟體動物嘅殼 都有浸硬淨嘅方解石外層

As the slightly more soluble molecule,

作為稍易溶解嘅分子

aragonite can better adapt to more or less acidic environments.

霰石會更適應或多或少嘅酸性環境

So most mollusk shells have an interior layer of aragonite

大多數軟體動物嘅殼都有浸霰石内層

to maintain their internal pH level.

嚟為持體内嘅pH 值

But one form of aragonite is stronger and more versatile than the rest:

但霰石嘅某種形態比 其他更堅固、更通用：

nacre.

珍珠母

Mollusks make this special material by placing successive layers of aragonite

軟體動物透過放置散佈蛋白質嘅霰石層

interspersed with proteins.

去製造呢種特殊材料

These layers are stacked like hexagonal bricks,

好似六角磚噉一層疊一層

each surrounded by other organic material that directs their orientation.

每層都俾其他有機材料包圍， 繼而决定方向

The uniform layering and brick-like structure of nacre

珍珠母劃一嘅分層同磚狀結構

is key to its signature iridescence.

係佢標誌性彩虹色嘅關鍵

The layers are similar in thickness to the wavelength of visible light,

霰石層嘅厚度同可見光嘅波長相似

so the light reflecting from its interior surface

所以喺佢內層表面反射嘅光

interferes with the light reflecting from the outer surface.

同由外層表面反射嘅光互相影響

When particles of light strike the nacre,

當光粒子撞擊珍珠母嗰陣

they bounce around its multilayered crystalline structure

佢哋會喺多層晶體結構周圍反彈

in a cascade of shifting rainbows.

形成一連串會郁嘅彩虹

But nacre isn’t just pretty—

但珍珠母唔單止靚

it’s one of the strongest and lightest biomaterials we know of.

仲係大家認為最硬最輕嘅生物材料之一

And it's not just oysters that produce it.

而且製造佢嘅唔止係蠔

In fact, numerous mollusk species deploy nacre

好多軟體動物都會運用珍珠母

as one of their primary defense mechanisms.

作為佢哋嘅主要防禦機制之一

If an intruding parasite or even a stray particle of sand irritates the mantle,

如果有寄生蟲入侵或沙粒碎刺激咗外套膜

the mollusk will coat the offender in nacre-producing cells

軟體動物用製造珍珠母嘅細胞包裹入侵物

to form what’s known as a pearl sac.

形成所為嘅珍珠囊

These cells wrap the threat in layers of proteins and aragonite

細胞將入侵物包裹喺蛋白質同霰石層中

until eventually the cocoon completely absorbs the invader—

直到最終個繭完全吸收入侵者

dissolving the threat into an opalescent sphere of nacre.

將佢溶解成奶白色球體珍珠層

This defense mechanism is our leading theory for mollusks making pearls;

個防禦機制係對於 軟體動物製造珍珠嘅主要理論

transforming everyday intruders into timeless treasures.

將日常入侵者變成永恆嘅寶藏