Fish Gills: Fish primarily rely on gills for respiration. When water flows over the gills, the blood vessels in the gill filaments exchange gases with the water.
Swim Bladder: The African lungfish can use its swim bladder for respiration, allowing it to survive for a period of time even when out of water.
Skin: Mudskippers can breathe through their skin and the mucous membranes in their mouths, but they must return to the water before drying out.
Intestine: Loaches can breathe through their intestines when oxygen levels in the water are low. They swim to the surface and inhale air into their intestines to breathe.
1. Fish Gills
All fish can breathe using their gills. Unlike land animals that breathe using lungs, fish gills only function in water. Under the gill covers, fish have gill filaments densely packed with blood vessels. As water flows over the gills, the direction of water flow is opposite to that of blood circulation, allowing efficient gas exchange. This enables fish to absorb oxygen and expel carbon dioxide.
2. Swim Bladder
In addition to gills, some fish have auxiliary breathing organs. The African lungfish, for example, can rely on its swim bladder for respiration. These fish are called lungfish because their swim bladder is structurally similar to a lung. Surrounding the central cavity are small air chambers, which are further subdivided into smaller air sacs, allowing the fish to store oxygen and continue breathing even when out of water for a while.
3. Skin
Mudskippers are small fish that live in temperate coastal areas, typically in shallow waters along the shore. When the tide recedes, they can move around on land to search for food. The reason these fish don’t die out of water is because they can breathe through their skin and the mucous membranes in their mouths. However, before drying out, they must return to the water.
4. Intestine
Loaches are fish that live at the bottom of rivers, lakes, and rice fields. They are nocturnal and highly adaptable. When the water becomes oxygen-deprived, these fish swim to the surface and inhale air into their intestines to breathe. Before the water dries up, they can bury themselves in the mud to continue surviving.
