Koža, ktorá vidí

Štvrté ráno sa Chiara oneskorila. Prišla s dvoma kávami z baru na rohu a vlasy mala vlhké od morského vánku. Jednu kávu položila na pult. "Včera večer ma napadlo," povedala. "Ešte sme neurobili farebný test pre Polly."

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."

Farebný test bol Pastin obľúbený, povedala Chiara. Na dno nádrže položila tri ploché taniere rôznych farieb. Jasne červený. Jasne modrý. Jasne žltý. Pod jedným z nich, pod malou plastovou kupolou, bol kúsok krevety. Dnes bola kreveta pod červeným tanierom.

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.

"Tu je tá vec," povedala Chiara. "Chobotnice sú farboslepé. Ich oči majú len jeden druh fotoreceptora, nie tri ako naše. Podľa všetkých testov, ktoré sme kedy robili len na ich očiach, chobotnice nedokážu rozlíšiť farby."

"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."

Polly naklonila svoju červenú hlavu.

Polly tilted her red head.

"A predsa," povedala Chiara. Ukázala na nádrž. "Sleduj."

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

Pasta sa rozvinula. Dve ramená sa natiahli cez dno nádrže. Prešli cez modrý tanier bez spomalenia. Prešli cez žltý tanier bez spomalenia. Zastavili sa nad červeným tanierom. Jedno rameno zdvihlo kupolu. Pasta si vzala krevetu.

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.

"Nie je slepá na farby," povedala Chiara. "Ale nie sú to jej oči, ktoré ich vidia."

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

Za posledných pätnásť rokov biológovia zistili, že koža chobotnice je plná buniek citlivých na svetlo nazývaných opsíny. Rovnaká molekula, ktorá vystiela ľudskú sietnicu, pokrýva celý povrch ramena chobotnice. Koža chobotnice dokáže detegovať svetlo na rôznych vlnových dĺžkach. U niektorých druhov dokáže koža detegovať konkrétne farby.

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.

Toto je jedna z možných odpovedí na otázku, ktorá biológov mátala sto rokov: ako sa farboslepé zviera dokáže tak dokonale maskovať v farebnom prostredí? Chobotnica na korale sa zhoduje s koralom. Chobotnica na piesku sa zhoduje s pieskom. Jej oči nevidia farbu. Ale jej koža áno. Koža vidí, čo potrebuje napodobniť.

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.

Pasta sa stiahla so svojou krevetou. Celý experiment trval menej ako minútu.

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

Polly pomaly kráčala po okraji nádrže. Nikdy predtým nerozmýšľala o svojich vlastných očiach. Jednoducho im dôverovala. Myšlienka, že zviera môže vidieť časťami svojho tela inými než očami, bola na chvíľu hlboko zvláštna. Pomyslela si, s malým závanom závratu, ktorý si zaslúžil, že nemá predstavu, čo väčšina jej vlastného tela vie.

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.

Chiara zdvihla svoju kávu. "Je to zaujímavé, nie?"

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

Polly naklonila svoju červenú hlavu.

Polly tilted her red head.

"Je toho viac," povedala Chiara. "Publikovali sme o tom články už desaťročie. Väčšina ľudí tomu stále nemôže uveriť. Koža zvieraťa vidí." Napila sa kávy. "Vitajte v časti biológie, kde toho vlastne veľa nevieme."

"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."