Respiration Fish Mechanism

Fish are aquatic animals that live in freshwater or saltwater, and the study of fish is known as Ichthyology.Unlike other animals, fish have a cold blood circulation (are poikilothermic). Despite their spindle-like shape, their bodies are sleek and well-defined. Dermal scales cover the body, which makes it water-resistant. Placoid, cycloid, ctenoid, and organoid scales are all types of scales. Fishermen use their fins as locomotory organs. Only internal ears are present, and they do not have eyelids or a nose. Known as a venous heart because of its two chambers, the heart is two-chambered. It is impossible to have a circuit in the blood circulation system. Unisexuality is the norm for fishes (i.e., internal or external fertilisation). Using their gills, fishes breathe. The majority of fish species have between 4 and 7 pairs of gills on their heads.

Respiration

Respiration is defined as the process of taking in oxygen and exhaling carbon dioxide in order to generate energy from the oxidation of complex organic compounds. Fishes breathe through their gills. Gills are present near the head and have a feathery texture, which allows them to allow water to enter while also allowing for the exchange of gases to occur. Located near the fish’s mouth cavity, the fish’s gills help it to breathe. Due to the presence of blood vessels, gills are a bright red colour. Fish exchange oxygen and carbon dioxide dissolved in water, which is beneficial to all living things. In addition to absorbing oxygen that is dissolved in water, Gills also release carbon dioxide. 

Respiration in fish

The gills of a fish are responsible for the process of respiration. The majority of fish have gills on either side of their heads. The filaments in fish gills are arranged in rows in the gill arch, which is the structure that holds them together. Each filament is made up of lamellae, which are discs that are filled with capillaries and are connected to one another by filaments. These small blood vessels are responsible for the movement of blood in and out of the gills. Despite the fact that fish’s gills only cover a small portion of their body, the extensive respiratory surface created by the filaments ensures that the entire organism is capable of efficient gas exchange.

Fish take in oxygen-rich water through their mouths and then pump it out through their gills to expel it. When water passes over the gill filaments, the dissolved oxygen is taken up by the blood within the capillary network of the fish. The circulatory system then transports oxygen to all of the body’s tissues and, finally, to the cells, while also absorbing carbon dioxide, which is expelled from the body through the gills. After water passes through the gills and exits the fish’s body through the openings provided in the sides of its throat or through the operculum, a flap that is usually found in bony fish and serves to cover and protect the fish’s gills, it leaves the fish’s body.

Lampreys and sharks, for example, are among the fish that have multiple gill openings. Rohu is a bony fish with a single gill opening on each side of its body

Countercurrent Exchange Mechanism

It is believed that this mechanism greatly improves gill efficiency in some mollusks and fishes because water flows across the gills in the opposite direction of blood flow, thereby increasing the efficiency of the gills. This, in turn, increases the efficiency of the gills by 90 percent, allowing for the recovery of dissolved oxygen from the water to be more efficient.

• Gill covers are found on both sides of the throat, protecting the gills (pharynx).
• When fish pull oxygen-rich water content through their mouths and pump it across their gills, they are exchanging gases with the surrounding environment.
• The remaining water is thrown away after the oxygen has been absorbed by the gills.
• Bony fishes have only a single gill opening, but some fishes, such as lampreys and sharks, have multiple gill openings to accommodate their large size.
• Gill openings are also referred to as gill slits in some circles.

How Do Some Fishes Breathe When They Don’t Have Gills? 

Although the majority of fishes in the ecosystem use their gills to breathe, some have evolved other means of accomplishing the same goal in order to survive. The following are the most significant of them all, in order of importance: 

• Respiration through the skin (gas exchange occurs across the skin of an organism instead of gills or lungs). 
• For instance, reedfish and mudskippers. The electric eel is capable of breathing through its buccal cavities. 
• Scolopacidae are a group of fishes that breathe through their digestive tracts. 
• Some fishes have additional breathing organs, such as labyrinth organs above the gills in labyrinth fishes, and other such organs.

Conclusion

Water contains both dissolved oxygen and dissolved carbon dioxide. The majority of fish have gills to aid in the exchange of gases and, more importantly, to breathe in water. It is present beside the pharynx and is covered by the operculum that gills are present. The countercurrent exchange mechanism of breathing is used by the vast majority of fish, in which the water flows in the opposite direction of the bloodstream, increasing the efficiency of gas exchange by 90 percent as a result. Due to the large surface area provided by lamellae’s folded structures, it is easier for gases to exchange between them. Because of the presence of blood vessels, the colour of the gills is a bright red. Several fishes have a swim bladder (also known as a hydrostatic organ), which is located between the kidney and the stomach and which allows them to control the depth of water they swim in by regulating the concentration of gas in the bladder.