孔雀魚：給你點“眼色”看看
科學家們發(fā)現，一般情況下小特立尼達孔雀魚的眼睛是銀色的，可當它們生氣的時候，它們的眼珠就會變成一片漆黑，警告其它孔雀魚滾開?？茖W家們發(fā)現這一現象的過程也很有趣。
Freshwater guppies - small, defenseless and popular as aquarium pets - are towards the bottom of the food chain, and when they experience a high level of predation, they don't display a lot of aggression.
淡水孔雀魚體型嬌小，手無寸鐵的它們適合當寵物。它們位于食物鏈底部，當它們體驗到掠奪行為的時候，也沒有太大攻擊性。
However, in safer environments, such as above waterfalls, they tend to get aggressive with each other, fighting over resources such as food - and, as previous research has observed, black eyes in some guppy species correlates with aggressive behaviour and dominance.
然而，在更安全的環(huán)境中，比如瀑布上方，它們通常會對彼此有攻擊性，為食物等搏斗。和先前研究中觀察到的一樣，某些孔雀魚有攻擊行為的時候，眼珠會變黑。
They can change their eye colour in just a few seconds. But whether the guppies were using this deliberately was unknown - so animal behaviour experts designed an experiment to find out.
它們的眼珠只會變黑幾秒鐘。但我們不知道這是不是孔雀魚故意為之，于是動物行為專家們進行了實驗。
"Experimentally showing that animals use their eye colouration to communicate with each other can be very difficult, so we made realistic-looking robotic fish with differing eye colours and observed the reaction of real fish," explained Robert Heathcote of the University of Exeter.
?？巳卮髮W的Robert Heathcote表示：“用實驗很難證明孔雀魚會利用眼睛顏色與彼此溝通，于是我們做了眼睛顏色不同的仿生機器魚，并觀察真魚的反應。”
They created a mould of a dead guppy, and created silicone replicas. Then they gave the replicas either black or silver eyes, based on photographs of living guppies, and put them on a fishing line attached to a motor.
他們做了一個死孔雀魚的模型，并做了硅膠復制品。接著他們給復制品安裝銀色或者黑色眼睛，給它們綁上馬達后，就將它們放進了真正的魚群中。
These robotic guppies were then placed over food, and made to appear that they were moving about. The team found that the other guppies were more likely to move in on the food if the robot had silver eyes than if it had black eyes.
這些機器孔雀魚被放在食物上方，并做出移動的樣子。該團隊發(fā)現比起黑眼睛機器魚，與銀眼睛機器魚爭奪食物的孔雀魚更多。
But if the black-eyed robot was smaller than the real guppies, it got disproportionately targeted by the real fish.
但如果黑眼睛機器魚比真正的孔雀魚小，那么它就會被真正的魚攻擊。
This is because the guppies, the researchers concluded, were using the black eyes as a signifier of what they call "honest" aggression.
研究人員們認為這是因為孔雀魚利用黑眼睛作為攻擊信號。
Not only do black eyes indicate an absolute willingness to enter an altercation, they also indicate that the black-eyed guppy has something worth defending.
黑眼睛不僅預示著孔雀魚想要打架，還預示著黑眼睛的孔雀魚擁有某些值得一戰(zhàn)的東西。
Hence the larger guppies targeted the small black-eyed robot - they knew that they would have the upper hand in an altercation, and that the smaller robot had something they would want.
于是體型更大的孔雀魚會攻擊體型小的黑眼睛機器魚，它們知道它們會贏，也知道小機器魚擁有它們想要的東西。
In the real world, smaller guppies don't tend to display black eyes to larger ones - it's only used by guppies against those they know they can dominate.
在現實世界里，小孔雀魚不會對大孔雀魚展示黑眼睛，它們只會對著能戰(zhàn)勝的對手展示黑眼睛。
Scientists still don't know how the guppies change the colour of their eyes, but the research is yet another demonstration of the importance of eyes in the animal kingdom.
研究人員們不知道這些孔雀魚怎樣改變它們的眼睛顏色，不過該研究再一次說明在動物王國中，用眼神示威十分重要。
"Eyes are one of the most easily recognised structures in the natural world and many species go to great lengths to conceal and camouflage their eyes to avoid unwanted attention from predators or rivals," said Darren Croft from University of Exeter."However, some species have noticeable or prominent eyes and, for the most part, it has remained a mystery as to why this would be. This research gives a new insight into the reasons behind why some animals have such 'conspicuous' eyes."
埃克塞特大學的Darren Croft說道：“眼睛是自然界最容易識別的結構之一，很多動物會隱藏或者偽裝它們的眼睛，以避開捕食者或者競爭對手的注意。然而，某些動物的眼睛十分引人注意，這對我們而言是一個謎。該研究讓我們從新的角度來了解背后的原因。”
The research has been published in the journal Current Biology.
該研究被發(fā)表在《當代生物學》期刊上。
