How do oysters make pearls? - Rob Ulrich

翻译人员: Grace Man 校对人员: Yip Yan Yeung

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

尽管大多数人并不觉得 牡蛎坚硬的外壳特别美丽，

to be particularly beautiful,

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

可是打开这凹凸不平的外壳，

可能会收获 一枚镶嵌在其中的精美珍珠。

Yet, despite their iridescent colors and smooth shapes,

珍珠光彩夺目，形状光滑，

pearls are actually made of the exact same material

但其实它与周围贝壳的 化学成分完全相同。

as the shell that surrounds them.

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

珍珠、海胆刺、贻贝的贝壳、 海螺和蛤蜊，甚至是珊瑚——

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

这些都是由相同的 化合物构成的：碳酸钙。

calcium carbonate.

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

那么，为什么这种单一的成分 可以组成如此种类繁多的物质呢？

Calcium carbonate, or CaCO3, is common on land,

碳酸钙，也叫做 CaCO3， 在陆地上很常见，

and even more bountiful in the sea.

而在海洋中还要更加丰富。

The Earth’s crust is rich in calcium,

地壳当中富含钙质，

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

数千年来，这些沉积物渗透至 河流与海洋当中，

This is especially true near hydrothermal vents,

海底热泉附近尤甚，

where hot seawater mingles with calcium rich basalts.

在这里，热泉海水与 富含钙质的玄武岩混合。

Meanwhile, when carbon dioxide in the air interacts with seawater

同时，空气中的二氧化碳 与海水发生化学反应，

it eventually produces dissolved carbonate.

最终生成溶解性碳酸盐。

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

海洋每年吸收了人类排放 二氧化碳总量的约 1/3 左右，

adding huge quantities of carbonate into the water.

并生成大量碳酸盐进入海水中。

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

海洋生物会利用这些产量丰富的 化合物，这并不令人惊讶。

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

不过，钙和碳酸盐交织出 不同形态物质的过程，

is surprisingly artful.

却充满令人讶异的艺术性。

Let’s return to the humble oyster.

回到看似不起眼的牡蛎。

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

与很多水生软体动物相同， 牡蛎的生命起始于暴露在外的幼体，

and quickly get to work building a protective shell.

然后迅速形成保护壳。

First, an organ called the mantle secretes an organic matrix

首先，一个叫做外套膜的组织

of proteins and other molecules to construct a scaffold.

分泌有机基质蛋白质与 其他分子来搭建支架。

Then, the oyster filters the seawater,

然后，牡蛎过滤海水，

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

取出其中的钙和碳酸盐，将它们 组合成保护壳的构成物质。

It lays this material over the scaffold,

它将这些物质置于支架之上，

which is covered in charged proteins that attract and guide

支架被带有电荷的蛋白质覆盖， 用以吸收并引领

the calcium carbonate molecules into layers.

碳酸钙分子形成分层。

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

这些蛋白质支架的特定排列取决于 软体动物种类以及它们的环境，

and their environment,

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

导致了贝壳形状、大小、 颜色的巨大多样性。

Mollusks carefully control all components of their calcium carbonate creations—

软体动物仔细地控制着它们 碳酸钙作品当中的成分含量——

even manipulating CaCO3 at the molecular level.

甚至在分子级别上操控着 CaCO3。

Using special proteins,

使用特殊的蛋白质，

mollusks can produce two crystal structures out of CaCO3:

软体动物可以生成 两种 CaCO3 结晶结构：

calcite and aragonite.

方解石与霰石。

Both of these compounds have the same chemical composition,

这两种化合物具有 相同的化学成分，

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

然而不同的晶体点阵排列 导致了它们拥有不同的特性。

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

在两者当中，方解石结构更稳定， 更不易随时间溶解，

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

所以大部分软体动物 有着方解石的坚硬外壳。

As the slightly more soluble molecule,

相对来说， 霰石是更加可溶性的分子，

aragonite can better adapt to more or less acidic environments.

能够更好地适应 或强或弱的酸性环境。

So most mollusk shells have an interior layer of aragonite

所以大部分软体动物有着 霰石的贝壳内侧，

to maintain their internal pH level.

来维持内部的酸碱值。

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

但霰石的其中一种形态要比其他 所有的都强度更大、用途更广：

nacre.

珍珠母（nacre）。

Mollusks make this special material by placing successive layers of aragonite

软体动物将霰石连续分层放置， 并在中间散布点缀蛋白质，

interspersed with proteins.

就得到了珍珠母这种特殊的物质。

These layers are stacked like hexagonal bricks,

这些分层像六角形砖块一般堆叠，

each surrounded by other organic material that directs their orientation.

每一块都被其他有机物包围， 来指引排列方向。

The uniform layering and brick-like structure of nacre

统一的分层与砖块形状的结构是

is key to its signature iridescence.

珍珠母拥有其标志性 流光溢彩的彩虹色泽的关键。

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

这些分层的厚度 与可见光的波长相似，

so the light reflecting from its interior surface

所以珍珠母内表面反射出的光

interferes with the light reflecting from the outer surface.

会和外表面反射的光产生 建设性或破坏性的干扰。

When particles of light strike the nacre,

当光粒子照射进珍珠母时，

they bounce around its multilayered crystalline structure

它们会在多层次的 晶体结构当中来回反弹

in a cascade of shifting rainbows.

呈现出变化无穷的彩虹色彩。

But nacre isn’t just pretty—

但是，珍珠母不单单是漂亮——

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

它还是目前已知的 最坚硬且最轻的生物材料。

And it's not just oysters that produce it.

不只是牡蛎会产生这种材料。

In fact, numerous mollusk species deploy nacre

事实上，众多软体动物种类都将 珍珠母作为它们的首要防御机制。

as one of their primary defense mechanisms.

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

当有寄生生物或沙粒等 进入软体时，

the mollusk will coat the offender in nacre-producing cells

软体动物会用珍珠母 产生的“囚室”困住入侵者，

to form what’s known as a pearl sac.

并形成珍珠囊。

These cells wrap the threat in layers of proteins and aragonite

这些“囚室”裹挟着外来威胁物， 将它们锁在蛋白质与霰石的夹层里，

until eventually the cocoon completely absorbs the invader—

直至最终夹层完全吸收了入侵者——

dissolving the threat into an opalescent sphere of nacre.

将威胁物溶解成为 珍珠母乳白色的球体外表。

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

这种防御机制就是 软体动物产生珍珠的主要理论；

transforming everyday intruders into timeless treasures.

将每天的入侵者变为 永不过时的珍宝。