玻璃蛙的神秘隱身術

Translucent Frog Optics Create Camo Color

玻璃蛙的神秘隱身術

Some ocean animals have a clever form of camouflage—they’re transparent. But being see-through is far less common on land.

有些海洋動物能夠很聰明的偽裝自己——因為它們是透明的。但在陸地上，透明的情況要少見得多。

「And there’s a few reasons why that may be.」

「這可能有幾個原因。」

Jim Barnett is a postdoctoral research fellow at McMaster University in Ontario, Canada. (He began this research as a doctoral student at the University of Bristol.)

吉姆·巴奈特是加拿大安大略省麥克馬斯特大學的博士後研究員。(他是在布里斯托大學攻讀博士學位時開始這項研究的。)

「Differences between air and water as a surrounding medium means that light interacts differently with a transparent organism’s body tissues.」

「周圍介質的空氣、水之間的差異意味著光與透明生物體的身體組織發生不同的相互作用。」

In the ocean, light is always coming from above, and the background is less variable. But in jungle canopy, light is coming from many directions, and the background is far more variable. Enter a little critter called the glass frog. It’s not actually transparent; it’s translucent. That means its skin in some places is thin enough that you can actually see its internal organs hard at work.

在海洋中，光總是來自上面，背景很少變化。但在叢林的樹冠上，光線來自不同的方向，背景也更加多變。一種叫做玻璃蛙的小動物。它實際上不是透明的;它是半透明的。這意味著它某些地方的皮膚足夠薄，你可以看到它的內部器官在努力工作。

「Most of the time, when you see photographs of these frogs, they’re taken under quite controlled conditions, with either strong lighting, like a powerful flash, or they’re photographed from underneath on a piece of glass, and it’s really their bellies which are transparent. And these frogs are pretty small and thin and quite delicate, so if you have a powerful flash on your camera, you can sort of just blast light through them, and they will look pretty transparent.」

「大多數時候，看到的這些青蛙的照片是在相當可控的條件下拍攝的，要麼用強光，要麼用強閃光，或者從下面的一塊玻璃上拍攝，它們的肚子是透明的。這些青蛙非常小，很薄，而且非常脆弱，所以如果相機上有一個強大的閃光燈，就可以把光通過它們，這些青蛙看起來會非常透明。」

Barnett says the frog’s translucent skin is actually a novel camouflage strategy that no one’s ever really studied—until now.

巴奈特說青蛙半透明的皮膚實際上是一種新的偽裝策略，直到現在還沒有人真正研究過。

「What we think is happening is that light is traveling through the frog, interacting with the pigmentation. But a lot of it does pass through the frog. Some of that light will be absorbed by the background underneath the frog. But some of it will be reflected off that background and come back through the frog.」

「我們認為是光線穿過青蛙，與色素發生作用。很多光線的確會通過青蛙的。部分光線會被青蛙下方的背景吸收。但有些會被背景反射，穿過青蛙回來。」

So if a glass frog is sitting on a bright green leaf, high in the jungle canopy, the light passing through its thin skin and onto the leaf will make the frog appear brighter in color, matching more closely with the leaf.

因此，如果一隻玻璃蛙坐在高高的叢林樹冠上一片明亮的綠色葉子上，光線穿過它薄薄的皮膚，照射在葉子上，就會使這隻青蛙的顏色顯得更亮，與葉子的顏色更接近。

The jungle canopy is filled with leaves, but it’s also filled with predators: birds, snakes, mammals and even invertebrates in search of their next meal.

叢林的樹冠上布滿了樹葉，但到處都是捕食者:鳥類、蛇、哺乳動物，甚至無脊椎動物在尋找它們的下一餐。

「And these animals are quite—their visual systems are pretty cued in to finding differences in luminance and brightness between different patches. So they’re quite good at finding prey based on differences between the background and the animal’s brightness. And by being translucent, it seems, these frogs are able to have an adaptive camouflage.」

「這些動物非常——它們的視覺系統非常善於發現不同斑塊之間的亮度差異。所以它們非常擅長根據背景和動物亮度的差異來尋找獵物。由於半透明的特性，這些青蛙似乎有了一種適應性的偽裝。」

So regardless of whether the leaf is dark or bright, if the glass frog is sitting on it, it will appear to change to more closely match its background. The study by Barnett and colleagues is in the Proceedings of the National Academy of Sciences.

所以不管葉子是暗的還是亮的，如果玻璃蛙坐在葉子上，它看起來會變得更接近背景。這項由巴奈特及其同事進行的研究發表在《美國國家科學院院刊》上。

With around 150 known species of glass frogs in the world, Barnett says the next project is to find out if the frogs』 translucency may differ based on their individual habitats. One thing is certain: it will be hard to see what they find.

世界上已知的玻璃蛙大約有150種，巴奈特說下一個項目就是要弄清楚這種蛙的透明度是否會因為它們各自的棲息地而有所不同。有一件事是肯定的:很難看到他們將發現什麼