How do fishes breathe underwater?
Fish have a number of ways of breathing underwater. The most common way is to use gills, which are thin, fleshy outgrowths from the sides of the fish that are covered with blood vessels. When water passes over the gills, the blood vessels absorb oxygen from the water and the fish breathes in.
Some fish also have a swim bladder, which is a sac of air that helps the fish to float. The swim bladder can also be used to help the fish breathe, by exchanging the air in the bladder for fresh air from the water.
Some fish, such as eels, have what are called accessory respiratory organs, which are used to supplement their gills. These organs can be things like lungs, or outgrowths of the gut that are full of blood vessels.
Finally, some fish live in waters that are so low in oxygen that they have to use a process called countercurrent exchange. This is where the blood flowing to the fish’s gills flows in the opposite direction to the water flowing over the gills. This allows the blood to pick up more oxygen from the water, and the fish can breathe in more easily.
Leave a Reply