孔雀鱼：给你点“眼色”看看
科学家们发现，一般情况下小特立尼达孔雀鱼的眼睛是银色的，可当它们生气的时候，它们的眼珠就会变成一片漆黑，警告其它孔雀鱼滚开。科学家们发现这一现象的过程也很有趣。
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.
淡水孔雀鱼体型娇小，手无寸铁的它们适合当宠物。它们位于食物链底部，当它们体验到掠夺行为的时候，也没有太大攻击性。
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，在更安全的环境中，比如瀑布上方，它们通常会对彼此有攻击性，为食物等搏斗。和先前研究中观察到的一样，某些孔雀鱼有攻击行为的时候，眼珠会变黑。
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.
它们的眼珠只会变黑几秒钟。但我们不知道这是不是孔雀鱼故意为之，于是动物行为专家们进行了实验。
"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.
埃克塞特大学的Robert Heathcote表示：“用实验很难证明孔雀鱼会利用眼睛颜色与彼此沟通，于是我们做了眼睛颜色不同的仿生机器鱼，并观察真鱼的反应。”
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.
他们做了一个死孔雀鱼的模型，并做了硅胶复制品。接着他们给复制品安装银色或者黑色眼睛，给它们绑上马达后，就将它们放进了真正的鱼群中。
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.
这些机器孔雀鱼被放在食物上方，并做出移动的样子。该团队发现比起黑眼睛机器鱼，与银眼睛机器鱼争夺食物的孔雀鱼更多。
But if the black-eyed robot was smaller than the real guppies, it got disproportionately targeted by the real fish.
但如果黑眼睛机器鱼比真正的孔雀鱼小，那么它就会被真正的鱼攻击。
This is because the guppies, the researchers concluded, were using the black eyes as a signifier of what they call "honest" aggression.
研究人员们认为这是因为孔雀鱼利用黑眼睛作为攻击信号。
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.
黑眼睛不仅预示着孔雀鱼想要打架，还预示着黑眼睛的孔雀鱼拥有某些值得一战的东西。
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.
于是体型更大的孔雀鱼会攻击体型小的黑眼睛机器鱼，它们知道它们会赢，也知道小机器鱼拥有它们想要的东西。
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.
在现实世界里，小孔雀鱼不会对大孔雀鱼展示黑眼睛，它们只会对着能战胜的对手展示黑眼睛。
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.
研究人员们不知道这些孔雀鱼怎样改变它们的眼睛颜色，不过该研究再一次说明在动物王国中，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."
埃克塞特大学的Darren Croft说道：“眼睛是自然界最容易识别的结构之一，很多动物会隐藏或者伪装它们的眼睛，以避开捕食者或者竞争对手的注意。然而，某些动物的眼睛十分引人注意，这对我们而言是一个谜。该研究让我们从新的角度来了解背后的原因。”
The research has been published in the journal Current Biology.
该研究被发表在《当代生物学》期刊上。
