๐Ÿฃ Do Fish Have Blood?

Yes, fish have blood and it is red in color. This red color is due to the presence of a red pigment called hemoglobin. However, note that some fish such as Antarctica icefish have colorless blood because they lack oxygen-carrying red blood cells in their blood. Fish have a single closed loop circulation system which is consists of a heart, gill capillaries, and body capillaries.

Image credit: Bicanski

Do fish have blood in their bodies?

Have you ever seen fish blood?

Yes, fish have red-colored blood similar to the blood of the humans. Normally, we donโ€™t see blood in the fish meat bought from the store. However, if you cut a freshly caught fish, you will notice blood vessels with red-colored blood. The reason we donโ€™t notice blood in fish meat bought from meat stores because during gutting a fish, the blood is drained out of the fish body. Sometimes, the blood of the fish may get coagulated and the blood vessels in fish fillet are too small that blood is not visible easily.

Read: ๐ŸŸ Can a fish survive in milk?

We all are aware of the circulatory system in our bodies. Now letโ€™s try to understand the blood circulation system in the fish and how it is different from the human circulatory system.

Fish Circulatory System

The circulatory system of the fish is a closed loop system consist of heart, gill capillaries, and body capillaries.

We know that mammals like humans have a double circulation system that has four chambers: right atrium, right ventricle, left atrium, and left ventricle. The deoxygenated blood from the body enters the right atrium and passes through the right ventricle. The blood in the right ventricle is pumped to the lungs to get oxygenated. This oxygenated blood again enters the left atrium of the heart. This oxygenated blood moves to the left ventricle from where it is pumped to all body parts.

Fish have single cycle circulation in which blood pumped from the heart first passes through the capillaries of gills where it gets oxygenated. Then blood gets distributed throughout all body parts. This blood now gets deoxygenated with the help of body capillaries and then, returns to the heart. Fish have a single heart that pumps the blood in a closed loop. It is consists of four parts: two chambers – atrium and ventricle, an entrance (sinus venosus), and an exit (bulbus arteriosus).  

Blood Circulation in Fish Body

The deoxygenated blood from the body enters into the fishโ€™s heart through veins and gets collected in a thin-walled sac called sinus venosus. Then, it moves to a large muscular chamber called atrium which acts as a one-way antechamber. The blood from the atrium then passes through another thick-walled muscular chamber called the ventricle which pumps the blood. This pumped deoxygenated blood enters a large tube called bulbus arteriosus which is the connected aorta. Through the aorta, blood reaches to gill capillaries where it exchanges oxygen and carbon dioxide. This oxygenated blood gets distributed all over the body. The blood flowing through the body capillaries again exchanges the gases and gets deoxygenated. This deoxygenated blood enters the heart through veins and the cycle continues.

Read: ๐Ÿฆˆ Do Fish Blink?

Why is fish blood red?

The blood of fish is red in color due to the presence of hemoglobin. Fish blood is consists of plasma and various cells such as erythrocytes (red blood cells) and leukocytes (white blood cells). The red color of blood is primarily due to red blood cells that contain hemoglobin. Hemoglobin is responsible for the transportation of oxygen throughout the body. Hemoglobin protein is made up of subunits called heme that is ring-shaped chemical structures. These heme have iron molecules in their center which gives the red color to the hemoglobin and to red blood cells. The blood of fish contains millions of red blood cells. Therefore, the color of the fishโ€™s blood appears red.

Read: ๐Ÿก Do Fish Drink Water?

Do fish have colorless blood?

Yes, some fish have colorless blood. You heard that right!

The Antarctic icefish have colorless blood due to the absence of red blood cells. Their blood lacks oxygen-carrying pigment called hemoglobin which is red in color. Antarctic icefish have evolved such that it doesnโ€™t need red blood cells to carry oxygen. They are able to survive because of their surrounding water that is Antarctic waters which are rich in oxygen. These icefish also have a big heart which pumps large amounts of blood throughout their body such that they get sufficient oxygen to survive.

Read: ๐Ÿก How Do Fish Mate?

What type of blood do fish have?

According to a study on fish, it is found that different fish have different blood types as they exist in humans. However, these blood types are not identical to human blood types. Research has found that the sockeye salmon species has at least eight different blood types.

Professor Atom

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Professor Atom is a science enthusiast and alumni of IIT Bombay. According to him, every question can be solved with curiosity and mind mapping. ( Curiosity = Asking Questions = Learning )

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