1 How do Angelfish Breathe? A Presentation for The Angelfish Society June 8, 2008 By Tamar Stephens

2 How Do Angelfish Breathe? “That’s easy,” you might say. “They breathe through their gills.” “That’s easy,” you might say. “They breathe through their gills.” Of course, you are right, but do you know how gills actually work? Of course, you are right, but do you know how gills actually work? Why can angelfish breathe underwater, but human beings can’t? Why can angelfish breathe underwater, but human beings can’t? Can angelfish breathe air when they are out of the water? Why or why not? Can angelfish breathe air when they are out of the water? Why or why not? Do angelfish inhale and exhale? Do angelfish inhale and exhale? How much oxygen do angelfish need in their water? How much oxygen do angelfish need in their water?

3 Why do we need to breathe in the first place? Because we need oxygen, right? Because we need oxygen, right? But why do we need oxygen? But why do we need oxygen? We need oxygen for a chemical reaction to “burn” glucose to release energy. This is how our cells obtain energy to function. We need oxygen for a chemical reaction to “burn” glucose to release energy. This is how our cells obtain energy to function. Carbon dioxide is a waste by-product, which we release when we exhale. Carbon dioxide is a waste by-product, which we release when we exhale. GLUCOSE + OXYGEN  CARBON DIOXIDE + WATER + ENERGY

4 How does oxygen get to our cells? Well, you probably all know the answer to this one. Well, you probably all know the answer to this one. We use our diaphragm and chest muscles to inhale to draw oxygen into our lungs and to exhale to get rid of carbon dioxide. We use our diaphragm and chest muscles to inhale to draw oxygen into our lungs and to exhale to get rid of carbon dioxide. The right side of our heart pumps blood to our lungs to pick up oxygen and get rid of carbon dioxide. The right side of our heart pumps blood to our lungs to pick up oxygen and get rid of carbon dioxide. Our lungs have numerous tiny balloon-like sacs that are full of capillaries. The capillaries absorb oxygen into the blood stream and give release carbon dioxide. Our lungs have numerous tiny balloon-like sacs that are full of capillaries. The capillaries absorb oxygen into the blood stream and give release carbon dioxide. Then the oxygen-rich blood returns to the left side of the heart to be pumped through our arteries to deliver oxygen to the cells in all parts of our body. Then the oxygen-rich blood returns to the left side of the heart to be pumped through our arteries to deliver oxygen to the cells in all parts of our body.

5 It works the same way in fish, sort of… In fish, it sort of works the same way. The heart pumps blood to the gills to pick up oxygen and release carbon dioxide. In fish, it sort of works the same way. The heart pumps blood to the gills to pick up oxygen and release carbon dioxide. But a fish heart is different from a human heart. Fish hearts only have two chambers! But a fish heart is different from a human heart. Fish hearts only have two chambers! After the heart pumps blood to the gills to pick up oxygen and release carbon dioxide, the blood flows to the rest of the body organs and tissues before returning to the heart. After the heart pumps blood to the gills to pick up oxygen and release carbon dioxide, the blood flows to the rest of the body organs and tissues before returning to the heart.

6 Do Fish Inhale and Exhale? No, they do not inhale and exhale! No, they do not inhale and exhale! Fish accomplish “breathing” in one of two ways. Fish accomplish “breathing” in one of two ways. Some fish, such as sharks, need to swim through the water constantly to maintain a flow of water across the gills. Some fish, such as sharks, need to swim through the water constantly to maintain a flow of water across the gills. Other fish, including angelfish, swallow water through their mouths into the gill chamber and expel it out through the gills. Other fish, including angelfish, swallow water through their mouths into the gill chamber and expel it out through the gills.

7 Gills have two main parts.

8 The Operculum The operculum, or gill cover, protects the fragile tissue of the gills. The operculum, or gill cover, protects the fragile tissue of the gills. The operculum also helps direct water to to flow through the array of gill filaments. The operculum also helps direct water to to flow through the array of gill filaments. Photo of leopard angelfish from Gil Repetto Operculum covers the gills.

9 Gill filaments and lamillae The gills consist of sheet-like filaments. The gills consist of sheet-like filaments. The filaments are transected by many small projections called lamillae, which contain tiny blood vessels. The filaments are transected by many small projections called lamillae, which contain tiny blood vessels. Lamillae are where gases are exchanged between the water and the blood stream. Lamillae are where gases are exchanged between the water and the blood stream. Gill lamillae provide lots of surface area for exchange of carbon dioxide and ogygen. Picture from

10 How do lungs compare with gills?

11 Air versus water – lungs versus gills Air contains about 20% ogygen, or 20,000 parts per million (ppm). Air contains about 20% ogygen, or 20,000 parts per million (ppm). Lungs extract about 25% of that oxygen when we breathe. Lungs extract about 25% of that oxygen when we breathe. Cold water only holds about 8 to 9 ppm dissolved oxygen. Warm water as found in our angelfish tanks, holds less oxygen - about 4 to 5 ppm! Gills extract about 80% of the dissolved oxygen from the water. Gills have a much harder job than lungs! They are also much more efficient!

12 So, can angelfish breath out of water? Alas, no, they cannot. Alas, no, they cannot. The reason is because all of the lamillae will collapse when the fish is removed from the water. So even if you keep the gill area moist, the fish will start to suffocate. The reason is because all of the lamillae will collapse when the fish is removed from the water. So even if you keep the gill area moist, the fish will start to suffocate.

13 Why can’t people breathe under water? Our lungs simply do not have enough surface area to extract enough oxygen from the water to keep us alive. So we will suffocate if we try to breathe water. Our lungs simply do not have enough surface area to extract enough oxygen from the water to keep us alive. So we will suffocate if we try to breathe water.

14 I hope you enjoyed this presentation. Hopefully you have a little more understanding of how gills work, and a new appreciation for the efficiency of this remarkable organ! Hopefully you have a little more understanding of how gills work, and a new appreciation for the efficiency of this remarkable organ!

15 The End Now back to the chat room for discussion!