What Is The Labyrinth Organ?




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I’m happy to announce we’re having a guest poster today. Izzy the Fish Girl from Sitting by the Koi Pond has written an article about the labyrinth organ for us – a must-read for any Betta or Gourami fan.

Siamese fighting fish (Betta splendens) are some of the world’s most popular aquarium pets. Their shape and long fins are easily recognized by many people. What most people don’t know is that they breathe air just like you and I. Betta fish are members of the family Osphronemidae. All of these fish are have to breathe air or else they will drown. These fish, which also include the popular gourami, breathe air with the use of their labyrinth organ (this has gained them the nickname labyrinth fishes). Today I will give you a little more insight into how this organ works and why it is so important that betta fish and gourami have access to the air.

There are over 370 species of fish that have the ability to breathe air. These fish fall into two categories: facultative and obligate. Facultative air breathers only use their ability when the oxygen in the water runs low. Obligate air breathers have to breathe air because their gills can’t take enough oxygen from the water. Betta and gourami fall into this category.
As I said earlier, gourami and betta take oxygen from the air with the use of their labyrinth organ. This organ is an extension of the gill plates (bone that anchors the gills) and is made of many folds of bone. Very small blood vessels run over these folds and take the oxygen from the air in a very similar manner to lungs. Below you see a drawing of a giant gourami’s (Osphronemus goramy) gills and the labyrinth organ.

When the fish gulps air it fills this chamber. When you see a bubble rise out of your betta’s mouth it is not burping but releasing the air from the labyrinth chamber. This strange organ also allows bettas to build bubble nests and certain species of Betta spp to be mouth-brooders. This means they carry their eggs in their mouth until they hatch instead of guarding a nest.

The strange little labyrinth organ makes bettas and gourami unique among fishes we commonly see in pet stores and in our tanks. But their ability to breathe air should never be used as an excuse to keep them in sub-standard conditions. They should be appreciated for their uniqueness and treated like any other tropical fish: with clean, warm water.

Because betta and gourami are obligate air breathers they have to take gulps of air even at night. For a fish with no large plants or decorations near the surface this often means sleeping on the substrate and dashing to the surface for air. To prevent the fish having to exert a lot of energy to make it to the surface, offer large floating plants like water sprite or have large-leafed plants like java fern close enough to the surface. The betta hammock is an artificial leaf if you don’t want to work with live plants. Don’t put it directly under the light as bettas enjoy sleeping in the shade.
Izzy the Fish Girl @ Blogspot
If you have any more questions, be sure to leave a comment below!

Check out the article on how to set up a brackish aquarium I wrote for Sitting by the Koi Pond in return here.

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10 thoughts on “What Is The Labyrinth Organ?”

  1. Hi. I’m pretty new to having a fish and made a terrible mistake by adding melafix to his tank the last time I changed it a couple weeks ago to treat an illness. When he didn’t improve, and declined further, as per instructions on melafix I added another dose. After much research I concluded that melafix is responsible for his rapid decline and difficulty breathing amongst other things.

    Is there anything I can do to help my little guy, he’s clearly miserable and on the brink of death?
    Can bettas recover from injury to their labyrinth organ?

    Please, any information you can provide is greatly appreciated. I hope to hear from you soon as he’s suffering.

    Upon determining that melafix and bettafix is toxic to Bettas I immediately removed him from his tank into a gallon bowl with fresh water treated only with quick start.

    • Hi Sarah,
      I know that some days have passed since you posted this, I hope your fish is doing better..
      If it’s any consolation, I’ve seen some other hobbyists talk about how it should be labeled much clearer on the bottle.
      I’ve tried doing some research, and there doesn’t seem to be any known reversal methods. I think you did the right thing by transferring him immediately. I would do a 100% water change on the main tank, run carbon, do another large water change, and then replace the carbon again. Also, add Indian almond leaves to help bolster his immunity.
      If your fish is really struggling and you don’t think there’s been any improvement in the last couple of days, I would say to humanely euthanize him :-(.
      Please let us know how things go..

  2. Hey there! Just wanted to correct the family name in this article, it is Osphronemidae, not Osmophrenidae. Great article though!

  3. This has been most helpful for my situation! My betta has a bubble like bump on his head. When I started doing research I noticed it’s right on the “air bubble induct to labyrinth” which lead me to this page 🙂 is it possible my betta had had poor air quality and his labyrinth is swollen?
    I have pictures but can’t attach. Please email me if you can!

    • Hi! Sorry to hear your Betta isn’t doing well. I usually refer people looking for a diagnosis to forums – multiple people with lots of experience will surely be able to help you out more than just me. Try looking for Betta forums and asking for help there! Be sure to post the photo and include as many details as you can.

      Good luck, hope your fish recovers!

  4. Hi there

    Yesterday i cleaned out my giant gourami fish pond. The fish must now weight close to 10 kilos and it is more than 8 years old. I often just take all the water out of the tank while it lies there quietly. I have noticed it comming to surface to gulp air so i thought it must have a lung like air bludder or something that it uses. I never knew that it has something called a labyrinth organ until i red this article. I LOVE GIANT GOURAMIES there are like cats and u can play with them with toy boats !!!

  5. This was a lot of fun, Mari! Thank you for writing your post about brackish aquariums! It really opened my eyes. Some day I might like to try one. Those mudskippers are just too cool!


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