Like all other living creatures, fish too need oxygen to breathe. Fish get their supply of oxygen from water. They take water into their mouths, which passes through their gills. A fish’s gills work only in water. This is why most fish die when they are out of water for long.
When water passes through the fish’s gills, it absorbs oxygen from the water and replaces it with carbon dioxide from the fish’s bloodstream. The water flows out under the gill’s cover and this process is repeated.
Some fish can live even when they are not in water?
- Climbing Perch: This fish can breathe in water as well as in air. It uses its tail to help it walk on dry land for short periods of time.
- Mudskipper: A mudskipper can take in oxygen from the air through its gills and skin, when not in water.
- Lungfish: A lungfish digs a hole in the mud and enters it and breathes air using its lungs. This usually happens in the dry season when there is not enough water.
- Snakehead: Is found in Africa and Asia, has chambers near its gills, meant for breathing. A snakehead can survive for long periods out of the water and also hibernates in mud during the summers.
Most fish have four gills in a chamber on each side of their heads. Each gill contains numerous gill filaments that can take oxygen from the water into the bloodstream. In turn, they remove carbon dioxide from the blood and expel it into the water. The African and South African lungfish are unusual because they breathe through their lungs and do not have gills. If they are held underwater, they will drown.
THINGS TO DO –
- Even though fish breathe mostly in water, visit your nearest aquarium shop to see how every once in a while, fish come out of the water to breathe.
- Name 5 mammals that can breathe in water as well as on land.