大千世界:电鱼（在线收听）

不知道大家听说过电鱼没有...它们往往生活在浑浊的水域当中，依靠发射电流探测出障碍物以及猎物的位置...原理和蝙蝠发出的超声波差不多...在今天的大千世界中，我们就来关注下这类不同寻常的鱼。


Don: Zzzzap! zzzzaapp!

Yaël: What are you doing, Don?

D: Yaël, I'm pretending I'm an electric fish having a conversation.

Y: Like an electric eel?

D: The so-called electric eel is one kind of fish that produces electrical discharges. They can emit very strong electrical charges, hundreds of volts stronger than a car battery! They use their electricity to shock and kill prey or deter predators. But there are hundreds of other fish species that produce relatively weak electrical discharges–much too weak to hurt or shock you or another fish.

Y: Why? Such weak electric signals don't seem very useful?

D: Weakly electric fish use their electric organ discharges for two important functions–communication and navigation. Since many electric fish are nocturnal or live in murky water, they have evolved the ability to "see" their surroundings using electricity. The electrical field they create reacts differently to different kinds of objects. For example, a rock, a fish and a plant each conduct electricity differently. The fish detect these differences using electric receptors in their skin, and so can move easily around obstacles and find food without using their eyes. The dark or murky water also makes it hard to find and communicate with others. But electric fish use their electrical discharges to send signals to one another. By varying the frequency or pattern of their electric organ discharges, these fish can create complex communication signals. Behavioral studies of electric communication in these fish have found that electric fish signal this way during courtship, territorial disputes and other social situations.

Y: Cool! So Electric fish use electricity instead of light and sound to find their way and talk to each other!

Discharge: 排放(物)
thunder and lightning caused by electrical discharges 由放电长生的雷电

emit: 散发,放射;发出
The chimney emitted thick smoke into the air.
烟囱向空中散发出浓烟。

Predator: 食肉动物;掠夺者,捕食者

Nocturnal: 夜间活动的
The owl is a nocturnal bird.
猫头鹰是夜间活动的鸟。

Murky: dark and difficult to see through 浑浊的，污浊的
She gazed into the murky depths of the water.
她注视着那幽暗的水底。

Detect: 发现,察觉;查出,看穿
I detected anger in her voice.
我察觉出她说话声里含着愤怒。
He soon detected the faulty valve.
他很快查到了出毛病的阀门。

Obstacle: 障碍(物);妨碍
His reluctance to compromise is an obstacle to his political success.
他不肯妥协是他政治上成功的一个障碍。
Her parents' opposition is an obstacle to her marriage.
她父母的反对是她结婚的障碍。

Vary: 使不同;变更;修改
He never varied his habits.
他从未改变过自己的习惯。

Courtship: (动物的)求偶
Courtship will include displays in which the male fluffs up his feathers.
鸟儿求偶的表现包括雄鸟抖松羽毛的炫耀行为。