1.But somewhere between 5 million and 14 million years ago, two major changes took place.
但在一千四百万年到五百万年前,发生了两个重大变化。
2.First, what we call a chance mutation.
第一个是我们称为的偶然突变。
3.A tiny genetic change occurred in that one Notothenioid species.
在那种南极鱼的基因中发生了微小的改变。
4.Its DNA allowed for the production of a special protein, a protein that prevents the fish from freezing.
它的基因产生了一种特殊的蛋白质,这种蛋白质能保护南极鱼不受冻。
5.The way this…this anti-freeze protein works is: it binds to any ice crystals that form inside the fish.
这种抗冻蛋白工作的原理是:它会附在鱼类体内的每一个冰晶上。
6.This binding action prevents the ice crystals from growing larger.
这种粘附能防止冰晶变大。这就能保护南极鱼不受冻了。
7.And this is what prevents Notothenioids from freezing.
在那时候,南极鱼所在水域还没有那么冷
8.Now, at that time, the waters the Notothenioids inhabited were still not freezing cold, so the protein didn’t really make a difference as far as the fish’s survival.
所以这种蛋白对于鱼类生存来说,并没有起很大作用。
9.But this would change, because in the same period of geologic time there was a shift in the earth’s continental plates.
但这很快就会改变,因为在同一地质时期,地球的大陆板块发生了变化。
10.Continental drift caused Antarctica to move apart from the landmass of South America and to drift into the Southern Polar Region.
大陆漂移导致南极洲从南美大陆中分离出来,漂流到南极区域。
11.This resulted in a powerful water current encircling Antarctica, which prevented the Antarctic waters from mixing with warmer water.
这导致南极洲被一股强水流环绕,阻止了南极洲水域和温度更高的水融合。
12.So the southern ocean, isolated from that warm airflow from the north, cooled down drastically, to the kinds of sub-freezing temperatures we associate with it today.
所以,南部海域与来自北方的暖气流隔绝了,大幅度降温,达到了低于结冰点的温度,也就是今天的温度。
13.Now, most fish species couldn’t survive in this frigid environment and they became extinct.
大部分鱼类在如此寒冷的环境下都无法生存,很快灭绝了。
14.But that one Notothenioid species, with its unique ability to produce that anti-freeze protein, thrived.
但那种南极鱼,有了独一无二的制造抗冻蛋白的能力,茁壮成长。
15.It had virtually the entire southern ocean to itself!
基本上整个南部海域都是它的了!