All living organisms have to breathe, exchanging oxygen and carbon dioxide with the environment. How do fish do it without lungs? This viewer question comes from Zambia.
Category
🗞
NewsTranscript
00:00Do fish breathe oxygen like humans do?
00:08All living organisms have to breathe, exchanging oxygen and carbon dioxide with the environment.
00:17Humans and other animals inhale oxygen because their bodies need it to work.
00:26When you breathe in, your lungs absorb the gas from the air and release it into your
00:32blood.
00:33It carries the oxygen to all parts of your body.
00:37There's also oxygen dissolved in water, but much less of it than in air.
00:44Fish don't have lungs.
00:45Instead, they absorb oxygen from the water with special organs, the gills.
00:52In many fish, the delicate gills lie laterally behind the head and are protected by bony
00:58covers.
00:59They consist of a series of stiff arches covered with filament structures made of thin and
01:04permeable tissue.
01:06The blood flows just beneath the surface of these fine gills.
01:11When a fish opens its mouth, it draws in oxygen dissolved in the water.
01:16When it closes its mouth again, the gill covers open and the water with the oxygen flows over
01:21and past the gills.
01:24The fish can absorb the oxygen from the water via the gills as it flows past.
01:30To do so, they have to be immersed in water.
01:34After absorption, the oxygen is transported all over the body by the blood, just like
01:39in humans.
01:40In the same way, carbon dioxide flows with the blood from the body back to the gills.
01:46Fish can therefore absorb oxygen and release carbon dioxide at the same time.
01:54Not all water has the same amount of oxygen.
01:58Running water contains more of it than standing water like that in a lake.
02:03Fish that live in rivers and brooks, like trout, need more oxygen than other species.
02:12Fish can also breathe through their skin, especially the young animals after hatching.
02:17However, commercial species like cod, loach, and sole can also absorb oxygen through their
02:24skin.
02:25That helps lower the strain on gill respiration and circulation.