淡水 08

The crocodile's jaws snap tight like a steel trap - once they have a hold, they never let go. It took over an hour to drown this full-grown bull. To surprise their prey crocodiles must strike with lightning speed. Here, only the narrowest line separates life from death. Most rivers drain into the sea, but some end their journey in vast lakes. Worldwide lakes hold 20 times more fresh water than all the rivers. The East African Rift Valley holds three of the world's largest: Malawi, Tanganyika, and Victoria. Lake Malawi, the smallest of the three, is still bigger than Wales. Its tropical waters teem with more fish species than any other lake. There are 850 different cichlids alone, all of which evolved from just one single ancestor isolated here thousands of years ago.

鳄鱼的颌骨像钢钳一样结实。它们一旦咬住就绝不放松。它花了一个多小时把这只成年雄角马拖入水中溺死。为了突袭猎物，鳄鱼的速度必须快如闪电。此时生与死只在毫厘之间。绝大多数河流都汇入大海，但也有一些河流在大湖里结束它们的旅程。从全世界范围来说，湖泊中蓄积的淡水量是河流的20倍。世界最大的湖泊中，东非大裂谷地区就有三个，它们是马拉维湖，坦噶尼喀湖和维多利亚湖。马拉维湖是三个湖中最小的一个，但它的面积比威尔士还要大。 这座热带湖中的鱼类是世界所有湖泊中最多的。单是丽鱼科鱼类就有850种，它们是从成千上万年前这里的单一祖先独立进化而来的。