Scientists have suspected for many years that fish might give off a chemical signal to warn other fish about the presence of predators. When a fish in a school is injured, for example, the rest of the school will panic and swim away in response.

 

　　Scientists dubbed this unknown chemical “Schreckstoff,” or “scary stuff” in German, but they didn’t know what it was composed of until recently.

 

　　A major component in fish skin, chondroitin sulfate, appears to be the mystery chemical. When a fish is wounded, this substance is converted by enzymes into sugary molecules that are then shed into the water.

 

　　Scientists tested one of those molecules, glycosaminoglycan chondroitin or GAG for short, on zebra fish. They found that the sugary warning is detected by special crypt cells in the brain’s scent processing olfactory bulb. This region is directly connected with higher areas of the brain and could initiate a quick flight response in fish.

 

　　Scientists have also found that closely-related species sometimes respond to each other’s warning signals, but unrelated species do not. This suggests that there may be a variety of sugary-smelling molecules, with each species producing their own version.

 

　　Because the zebra fish brain is relatively simple, this research is allowing scientists to investigate at the cellular level what happens in the brain when an organism detects danger. It will allow them to see how groups of neurons regulate behavior and emotional responses.

 

　　Fortunately, fear doesn’t smell sweet for humans. We can enjoy all the apple pie, ice cream, candy and cookies that we want.

 

 

 

 

　　恐惧闻起来像糖

 

　　多年来科学家们一直都在怀疑鱼会释放一种化学信号来警告其他鱼类捕食者的出现。比如说，当鱼群中的一条鱼受到伤害时，鱼群中的其它鱼将会感到恐慌并且四散游开。

 

　　科学家将这种未知的化学物质命名为“Schreckstoff”，德语译为“令人恐惧的东西”。但是直到最近他们才知道这种物质的组成。

 

　　鱼的表皮中有一种叫硫酸软骨素的主要成分，似乎就是那种神秘的化学物质。当有一条鱼受伤时，这种物质就会通过酶的作用转化成含糖分子释放到水中。

 

　　科学家们测试了用斑马鱼释放出来的分子中的其中一个，可称为葡糖胺聚糖硫酸软骨素或简称为GAG。他们发现这种含糖的警告可以被特殊的隐窝细胞检测到，而隐窝细胞存在于大脑处理气味的嗅球中。这一区域和大脑更高级的区域相连，可以刺激鱼快速逃跑。

 

　　科学家们还发现亲缘关系很近的物种有时也对彼此的警报信号有反应，但是不同的物种就不会有反应。这告诉我们可能会有各种各样闻起来像糖一样的分子，每个物种会产生它们自己的版本。

 

　　因为斑马鱼的大脑构造比较简单，这项研究让科学家们可以在细胞水平上研究当生物遇到危险时大脑的反应机制。也可以研究神经组织是如何控制行为和情感反应的。

 

　　幸运的是，人类的恐惧闻起来不像糖。我们可以尽情的吃我们想吃的苹果派，冰激凌，糖果和饼干。