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Scientists have suspected for many years that fish might giveoff a chemical signal to warn other fish about the presence of predators.
多年來科學家們一直都在懷疑魚會釋放一種化學信號來警告其他魚類捕食者的出現。
When a fish in a schoolis injured,
比如說，當魚群中的一條魚受到傷害時，
for example, the rest of the school will panic and swim away in response.
魚群中的其它魚將會感到恐慌并且四散游開。
Scientists dubbed this unknown chemical “Schreckstoff,”
科學家將這種未知的化學物質命名為“Schreckstoff”，
or “scary stuff” in German,
德語譯為“令人恐懼的東西”。
but theydidn't know what it was composed of until recently.
但是直到最近他們才知道這種物質的組成。
A major component in fish skin, chondroitin sulfate,
魚的表皮中有一種叫硫酸軟骨素的主要成分，
appears to be the mystery chemical.
似乎就是那種神秘的化學物質。
When afish is wounded,
當有一條魚受傷時，
this substance is converted by enzymes into sugary molecules that are thenshed into the water.
這種物質就會通過酶的作用轉化成含糖分子釋放到水中。
Scientists tested one of those molecules, glycosaminoglycan chondroitin or GAG for short, onzebra fish.
科學家們測試了用斑馬魚釋放出來的分子中的其中一個，可稱為葡糖胺聚糖硫酸軟骨素或簡稱為GAG。
They found that the sugary warning is detected by special crypt cells in the brain'sscent processing olfactory bulb.
他們發現這種含糖的警告可以被特殊的隱窩細胞檢測到，而隱窩細胞存在于大腦處理氣味的嗅球中。
This region is directly connected with higher areas of the brainand could initiate a quick flight response in fish.
這一區域和大腦更高級的區域相連，可以刺激魚快速逃跑。
Scientists have also found that closely-related species sometimes respond to each other's warningsignals,
科學家們還發現親緣關系很近的物種有時也對彼此的警報信號有反應，
but unrelated species do not.
但是不同的物種就不會有反應。
This suggests that there may be a variety of sugary-smellingmolecules,
這告訴我們可能會有各種各樣聞起來像糖一樣的分子，
with each species producing their own version.
每個物種會產生它們自己的版本。
Because the zebra fish brain is relatively simple,
因為斑馬魚的大腦構造比較簡單，
this research is allowing scientists to investigate atthe cellular level what happens in the brain when an organism detects danger.
這項研究讓科學家們可以在細胞水平上研究當生物遇到危險時大腦的反應機制。
It will allow them tosee how groups of neurons regulate behavior and emotional responses.
也可以研究神經組織是如何控制行為和情感反應的。
Fortunately, fear doesn't smell sweet for humans.
幸運的是，人類的恐懼聞起來不像糖。
We can enjoy all the apple pie, ice cream, candyand cookies that we want.
我們可以盡情的吃我們想吃的蘋果派，冰激凌，糖果和餅干。
