Fish Gills: Fin-Tastic Facts About The Function Of Their Slimy Scales | Kidadl


Fish Gills: Fin-Tastic Facts About The Function Of Their Slimy Scales

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Fish need oxygen to live.

The gill structure is very different as compared to the lungs we humans have. Taking in oxygen as the release of carbon dioxide is the same.

They take it from the water rather than directly from the air. For this, they have a special respiratory organ called the fish gills. Fish gills' function is to absorb the dissolved oxygen from water. They gulp in water from their mouths and release the water from their gills. The gills of fish are a series of filaments that are on the side of the head.

The fish gills have various small blood vessels that are all lined up. These blood vessels work as capillaries. When a gush of water rushes through the system of the fish, it enters from the mouth, and these capillaries absorb the oxygen from the water. Then it is released through the lungs. Oxygen is used by the body for its functions.

This oxygen is carried by the blood throughout the rest of the body of the fish in a similar manner to that of humans. Fish are known to have an operculum, which is the bony plate that is used by the fish to open and close the gills so that there is no reversal of the process. Water only goes out and does not flow back in. Also, it makes sure that the gills are safe from any impact or damage.

There are many other marine animals in the world. They all do not have the same set of gills. There are some fish that have gills outside of their bodies as well. Nudibranchs, or sea slugs, have them displayed outside the body. These gills are generally colorful and present on the back of the species. So, when the water flows through them, they take the oxygen dissolved in the water.

Breathing in water is a tedious job. Humans cannot breathe underwater or take oxygen from the water like fish. The pressure water exerts on the body is another factor that hampers the breathing process.

In the air, the concentration of oxygen is 200, 000 per million. When this is compared to the diffusion in the water, you can see it is just four to eight parts per million. So, the amount of water needed to get the same amount of oxygen is much greater. The fish gill system is highly efficient in extracting oxygen from water.

The functions of the various respiratory organs are very complex and different. But the main aim is to transfer oxygen from the source to the blood so that it can be used by the body.

If you enjoyed this article, why not also read about ancient fish or fish that eat snails here at Kidadl?

Are fish gills like lungs?

Fish do not breathe in and out through their gills as humans do in their lungs.

The fish gills are a one-way passage. Water comes in, they absorb oxygen, and then it is released. It is like a ventilation system. Water flows in a single direction. When the water passes over the gill on the way, the oxygen is extracted. Also, the gills are very fast. This whole exchange does not take much time.

The water is released through the opercula, which is the bony cover over the gills. Other than this bony part, the gills are quite similar to the lungs. Both the organs have a high surface area so that maximum oxygen can be taken in. The larger the area, the more air or water comes into contact. Both the lungs and the gills have very thin walls. These are comprised of blood vessels or capillaries. The whole structure is different, but the purpose is the same.

The fish control the amount of water to be processed at a given time as they close their mouths after a big gulp of water. Carbon dioxide is released through the gills and is a waste product for the body. Other than this, there are many more uses for the gills in the body of the fish.

The gills help regulate and control the amount of salt that can remain in the body of the fish. The excess salt is released into the water.

So, we can say that the main difference between the lungs and gills is the working concept. The gills specialize in breathing in the water, while the lungs are used for breathing in air. There are more tetrapods present in the gills than in the lungs. Gills are basically a series of filaments all aligned in a row, and there are many such rows together. While the lungs are big bags that are filled and emptied with the help of tubes that are our airways.

Close up gill infected of Koi fish.

What are gills?

Gills are the respiratory organs that are used by fish to exchange gases. They are the same in nature, taking in oxygen from water and releasing carbon dioxide.

You may be amazed to know that a number of species of amphibians, annelids, and arthropods have gills for breathing. They can be known as the convoluted growth that surrounds the series of blood vessels. A thin epithelial layer is known to cover gills from the exterior. This layer plays a major role in protecting the gills from any damage.

Gills are internal organs in fish and crabs, while they are external organs in species of amphibians living close to the sea. Gills occur in an arrangement just behind the head. Openings from the esophagus run in a series and lead to the exterior gills of these animals. While mostly, you can see a cartilaginous arch that can be seen supporting gills. 

The comb-like filament set in a series of gills is called gill lamellae. This series arrangement enhances the total surface area that the gill acquires and uses to process, which increases the surface area of the gills. When the fish breathe, they gulp in a mouthful of water and then process it. The water is then forced through the set of filaments of the gill. Here the oxygen is extracted.

There is generally more than one set of filaments. You may see there are mostly three or seven rows of gill arches of fish, red gills all lined across the same area. Science has shown that breathing in water is a much more difficult job compared to breathing in air, so the fish need multiple gill structures.

How do gills work?

Gills have the same nature as the lungs, but they are larger in number.

The filaments are heavier in mass as well. They work in the same manner as the lungs. Their job is to extract oxygen from water and gas exchange is done. The oxygen requirement will vary according to the mass of the fish. All the other waste products flow out with water. The transfer is done with the pressure of water. It is believed that gills help maintain the salt level in the body of the fish.

The water is forced under pressure to flow through the filaments in the gills. During this short time, only the transfer of oxygen and carbon dioxide takes place. The oxygen is then taken in by the larger surface area of the gill. It is carried into the blood vessels and used in the entire body.

It is interesting to know that betta fish gills are used by the fish to expand and show that they are big in size. They do this to defend themselves or to attract mates. Also, it is believed that vestigial fish gills are the remains of the ears that may have existed in the fish or other aquatic animals.

Breathing Without Gills

There are marine animals other than fish that do not have gills. There are also fish without gills.

Whales are the only known fish without gills. They cannot process water to get oxygen. Instead, they need to come up to the surface to breathe and take in oxygen. They are different than the fish with gills. Fish like mudskippers are also included in this category.

These fish cannot stay underwater for very long or dive very deep. They sleep close to the surface of the water so that they can keep their nose close to the water and get uninterrupted air.

There are a variety of fish that can breathe through their skin. The breathing mechanisms are different, they absorb oxygen directly. The eels use a cavity called the 'buccal cavity' to breathe air. Catfish are known to use their digestive tracts to absorb air. They get oxygen directly.

Helping Fish With Hurt Gills

Sometimes fish may have hurt gill. Fish bleeding from gills can be common in all species when they are hurt.

This type of problem can arise when there has been an attack or a fight among the fish. The fish in your tank, even if they are the same species, can fight for mating and hurt their gills.

You can see the fish gills are red. That is not a matter of concern. As mostly they are made up of blood vessels all across. So, the color is deep red.

You can treat your fish in the tank by adding the medicine to the water. So, when this water passes through the gill with pressure, the medicine will reach it. In the event that it does not work, you will have to visit the vet. There may be a chance of branchiomycosis.

Branchiomycosis, a fungal infection, can be a cause of the gill problem. This can be a serious and deadly infection. It can occur if the water conditions are not healthy for the fish. You should not just clean the water but keep the pH and minerals in an adequate range. The temperature must not be too high this will increase the infection.

You can see that the gills are decaying and may seem to protrude at times. You must rush to the vet. Also, do not take the fish out of the tank, but do keep a close eye on the health of your fish to keep it happy and live a long life as your companion.

Here at Kidadl, we have carefully created lots of interesting family-friendly facts for everyone to enjoy! If you liked our suggestions for fish gills, then why not take a look at do fishes have teeth or Koi fish facts.

Written By
Sakshi Thakur

With an eye for detail and a penchant for listening and counseling, Sakshi is not your average content writer. Having worked primarily in the education space, she is well-versed and up-to-date with developments in the e-learning industry. She’s an experienced academic content writer and has even worked with Mr. Kapil Raj, a professor of the History of Science at the École des Hautes Études en Sciences Sociales (The School for Advanced Studies in the Social Sciences) in Paris. She enjoys traveling, painting, embroidery, listening to soft music, reading, and the arts during her time off.

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