能看见的皮肤

第四天早晨，琪亚拉迟到了。她提着两杯咖啡走进来，头发被海风吹得湿漉漉的。她把一杯咖啡放在柜台上。“我昨晚想到一个问题，”她说，“我们还没有给波莉做颜色测试呢。”

The fourth morning, Chiara was running late. She came in carrying two coffees from the bar on the corner and her hair was wet from the sea breeze. She set one coffee on the counter. "I had a thought last night," she said. "We have not done the colour test for Polly."

琪亚拉说，颜色测试是帕斯塔最喜欢的。她在水箱底部放了三只不同颜色的平盘。鲜红色。亮蓝色。明黄色。在其中一个盘子下，一个小塑料罩子里有一块虾肉。今天，虾肉在红色盘子下面。

The colour test was Pasta's favourite, Chiara said. She set out three flat plates of different colours on the tank floor. Bright red. Bright blue. Bright yellow. On one of them, under a small plastic dome, was a piece of shrimp. Today, the shrimp was under the red plate.

“事情是这样的，”琪亚拉说，“章鱼是色盲。它们的眼睛只有一种光感受器，而不是像我们一样有三种。根据我们对它们眼睛所做的每一个测试，章鱼是无法区分颜色的。”

"Here is the thing," Chiara said. "Octopuses are colour-blind. Their eyes have only one kind of photoreceptor, not three the way ours do. By every test we have ever done on their eyes alone, octopuses cannot distinguish colours."

波莉歪着她红色的头。

Polly tilted her red head.

“然而，”琪亚拉说。她指着水箱。“看。”

"And yet," Chiara said. She pointed at the tank. "Watch."

帕斯塔舒展开来。两只触腕伸向水箱底部。它们经过蓝色盘子时没有停顿。经过黄色盘子时也没有停顿。它们在红色盘子上方停住。一只触腕抬起罩子。帕斯塔拿走了虾肉。

Pasta uncurled. Two arms went out across the tank floor. They passed over the blue plate without slowing. They passed over the yellow plate without slowing. They paused over the red plate. One arm lifted the dome. Pasta took the shrimp.

“她不是对颜色视而不见，”琪亚拉说，“但不是她的眼睛在看。”

"She is not blind to colour," Chiara said. "But it is not her eyes that see it."

在过去的十五年里，生物学家发现章鱼的皮肤充满了叫做视蛋白的光感细胞。人类视网膜上的同一种分子覆盖了整个章鱼触腕的表面。章鱼的皮肤可以检测不同波长的光。在某些物种中，皮肤甚至可以检测特定的颜色。

In the last fifteen years, biologists have discovered that the skin of an octopus is full of light-sensing cells called opsins. The same molecule that lines a human retina lines the entire surface of an octopus arm. The octopus's skin can detect light at different wavelengths. In some species, the skin can detect specific colours.

这是一个可能的答案，解开了困扰生物学家百年的谜题：一只色盲的动物如何能在五彩缤纷的环境中如此完美地伪装自己？珊瑚上的章鱼与珊瑚融为一体。沙地上的章鱼与沙地融为一体。它的眼睛看不见颜色，但它的皮肤能。皮肤看见了需要模仿的东西。

This is one possible answer to a question that had puzzled biologists for a hundred years: how does a colour-blind animal camouflage itself so perfectly into colourful environments? An octopus on coral matches the coral. An octopus on sand matches the sand. Its eyes cannot see colour. But its skin can. The skin sees what the skin needs to copy.

帕斯塔带着她的虾肉退了回去。整个实验不到一分钟。

Pasta withdrew with her shrimp. The whole experiment had taken under a minute.

波莉慢慢沿着水箱边缘走。她从未想过自己的眼睛。她只是信任它们。一个动物可以用身体的其他部分来“看”的想法，一时间让她感到极为陌生。她想，她对自己身体的大部分所知甚少，这种想法带来了一阵轻微的眩晕。

Polly walked along the rim of the tank slowly. She had never thought about her own eyes before. She had simply trusted them. The idea that an animal could see with parts of itself other than its eyes was, for a moment, deeply strange. She thought, with the small flutter of vertigo it deserved, that she had no idea what most of her own body knew.

琪亚拉拿起她的咖啡。“很有趣，不是吗？”

Chiara picked up her coffee. "It is interesting, no?"

波莉歪着她红色的头。

Polly tilted her red head.

“还有更多，”琪亚拉说，“我们已经发表了十年的论文。大多数人仍然无法相信。动物的皮肤会‘看’。”她喝了一口咖啡。“欢迎来到生物学的领域，我们其实知道得不多。”

"There is more," Chiara said. "We have published papers on this for a decade. Most people still cannot believe it. The animal's skin sees." She drank the coffee. "Welcome to the part of biology where we don't actually know much."