科学揭秘：水中的鱼也需要喝水吗

Fish live in water, but do they drink it?



Fish live in water, but do they drink it?
鱼儿生活在水里，那么它们喝水吗？

The answer is yes, but how fish drink water depends on where they live.
答案是肯定的，但是鱼儿怎么喝水取决于它们生活在哪。

Water gets into a fish's body through osmosis, the process in which water diffuses from a higher to a lower concentration. For example, if there is more water outside of a cell than inside, water will try to flow into the cell until there is the same concentration of water on either side of the cell's membrane. The body of a fish acts the same way, either absorbing or losing water depending on its surroundings.
水通过渗透作用进入鱼的身体，也就是水从高处向低处的流动的过程。比如，如果某个细胞外面的水比细胞内的水多，水就会从外面流入细胞中，直至细胞内外的水达到同一浓度为止。鱼体内的水也以相同的方式运动，水分的吸收或者散发取决于周围的环境。

Whether a fish absorbs or loses water is based on the fact that all fish must maintain a certain amount of salt in their bodies to stay healthy. Fish that live in fresh water have a higher concentration of salt in their bodies than the surrounding water. Consequently, water continuously flows into the fish's body to attempt to dilute the amount of salt in the fish until it is equal to the amount of salt in the surrounding water. Since fish cannot allow their salt content to be diminished, their kidneys work overtime to expel excess water in the form of urine.
鱼是否吸收、释放水分取决于其必须确保机体内的盐分含量。淡水鱼体内的盐分含量要比它生活的淡水的盐分含量高，所以水会自然的进入鱼的体内以稀释其体内的盐的含量，直到鱼体内盐的含量与它生活的水域的盐含量相当。因为鱼类不能让体内的盐份流失，它们的肾脏会不停地工作以排尿的方式排除体内多余水份。

Ocean fish have the opposite problem. Surrounded by salt water, their bodies contain a relatively lower concentration of salt than the ocean water. In this case osmosis causes the fish to constantly lose water in order to equalize salt concentration inside and outside the fish. to partially compensate for the water loss, ocean fish actually drink water through their mouths. And to get rid of the excess salt they take in by drinking seawater, they excrete some salt through cells in their gills.
海水鱼的问题正相反。因为被盐水包围，所以它们体内盐的含量相对来说比周围的海水低。这样，渗透作用就使鱼经常释放水分以保证身体内外盐的浓度相等。为了补偿这种水分的散发，海水鱼就常常需要通过吐泡泡来摄入水并排出它们所喝的水中多余的盐分，它们通过鳃里面的一些细胞来排出盐分。