Fish Facts

Do Fish Have Blood in Them?

Fish have blood in them and also blood vessels. Here are the 11 interesting facts about the blood circulation in fish.

Do Fish Have Blood in Them? Most owners have this question about their fish that if their fish have blood in their body or not, and the answer is yes. Like other living organisms, fish also have blood in the bodies that perform several functions. The amount of blood is too little, but it is present and circulates in the vessels. Most of the fish species have red color blood, but in some species, the blood is colorless.

Do Fish Have Blood in Them?

Living organisms need several nutrients to survive and grow, and they require a medium that can carry and transport all these nutrients to every cell of their body.

Blood is the medium in living organisms that serves the function of transporting minerals and excreting wastes. Fish being living organisms also require this transporting medium, and blood functions the same way in humans and fish.

Blood contains several other necessary factors and components essential for fish, such as red blood cells, white blood cells, and thrombocytes.

All these cells play roles in fish survival and health by supplying oxygen and improving immunity. The blood in fish varies in color and amount, and you can say smaller fish have less blood while larger ones have more.

It is usually unobvious that a fish has blood because you can not see it even after cuts or wounds, but the fact is accurate; fish do have blood.

Why blood in fish is not visible?

Confusion arises when fish-keepers ask about blood in the fish, which is its visibility. As fish are small in size, they have small-sized body structures, small organs, and small blood vessels.

These thin, narrow, and minute vessels contain less amount that a person can not notice. These vessels are not too extended or spread in the body, so it is hard to see blood.

The best location to observe blood is the gills of fish, as they are red because of blood. However, it is necessary to understand that finding blood in a living fish is not easy.

The beating of the heart and respiration process is enough to believe that fish contain blood in the body. 

Like other living organisms, you can not see blood through the skin unless there are some cuts or bruises. Moreover, the color of blood is not always red in fish, and it may be colorless, so you can not see.

Whatever be the reason, but you should learn that your fish contains blood that circulates through a proper mechanism in their body.

How much blood does fish have?

The amount of blood in the fish depends upon the size of the fish. Smaller fish have few blood vessels, therefore, containing less amount of blood. Larger ones have more amount of blood in their body due to containing more and wide vessels.

You can say, a juvenile and young fish will have less blood than an adult and completely-grown one because of the difference in body size.

On this account, it is right to say that a fish has a blood weightage of about 10 to 12% of its total body weight. So, a fish weighing 10 lbs contains around 1 to 1.5 pounds of blood circulating in its body. This percentage is not correct for all the species and may vary depending upon species and family.

Why do fish not bleed?

Fish usually do not bleed, which does not mean that they lack blood, but it is due to minute quantity.

You know that your fish is too shorter, and this small one will not have much blood, so bleeding from cuts or wounds is uncommon and unexpected often. 

It is impossible to observe bleeding in small fish, but you can see bleeding from deep cuts in larger ones.

Although the blood is not visible, you can see red muscles from some deep cuts, indicating hemoglobin. Hemoglobin is the constituent of red blood cells, giving them the red color. 

Also, in some species, the blood is colorless, so you do not distinguish, and you think the liquid is not blood, but it is transparent blood.

Also, the blood may clot in the cut or wound area, so you do not see it, or the cut is not too deep to damage vessels or capillaries and cause bleeding.

What is the color of fish blood?

Usually, the blood is red due to containing hemoglobin molecules, which gives it its deep red coloration. The hemoglobin molecule is essential to supply oxygen to the body cells along with its characteristic coloration.

The blood color ranges from deep-red to bright-red, and it depends upon oxygen levels and the number of red blood cells.

In some fish, the blood lack typical red coloration and is usually colorless. These species lack hemoglobin and red blood cells, which makes their blood colorless.

This type of blood is clear and transparent, lacking every sort of coloration. It looks like a clear liquid that confuses people about whether these fish lack blood.

Why some fish have colorless blood?

Sometimes, the fluid present in some fish does not look like blood because of lacking red pigment, but it is also the blood.

As hemoglobin is the integral element of providing red color to the blood, so their absences these fish is responsible for colorless blood. Understanding this lack of coloration is complex but making it simple, you can say it is because of genetic mutation. 

The mutation occurs in the red blood cells that carry hemoglobin, which ultimately leads to the absence of these compounds.

No hemoglobin means not molecules to bind most of the oxygen in the blood, so these species have blood with low oxygen levels. In general, we can say their oxygen-carrying capacity is only 10 to 12% compared to other red-blood containing species.

These species are less, and probably they are the only vertebrates on earth that carry colorless blood. They have bid size heart that pumps a large volume of blood to supply a sufficient amount of oxygen to the cells.

Which type of fish have colorless blood?

There are only single species when it comes to having colorless blood, which is antarctic icefish. These fish are habitual in living in cold water that contains more amount of oxygen to survive. 

The water is too cold, and their body is habitual to such freezing temperature. This oxygen-rich water helps to take in more oxygen into the body to prevent any deficiency. Some common species of antarctic icefish are:

  • Chaenocephalus aceratus
  • Mackerel icefish
  • Chionodraco rastrospinosus
  • Channichthys
  • Cryodraco

Do fish have red blood cells?

Red blood cells are responsible for red coloration and the supply of oxygen, and they are the main components of fish blood, excluding icefish.

Mature red blood cells contain a considerable amount of hemoglobin, and these cells keep producing in the body throughout life. The number of red blood cells is not constant, and they keep changing with the season, age, and environment. 

Their number also vary in different species of fish belonging to families and classes. These cells are round to oval in shape, having red pigment.

They have a nucleus in the center of every cell. With time and maturation, these cells change in shape, but these changes are not extreme. 

Severe changes in cell-shape and sizes occur in disorders or mutations.

Do fish have white blood cells?

White blood cells or leucocytes make up a significant percentage of weightage in fish blood as they are the main constituents of the immune system. 

A fish has two types of white blood cells include agranulocytes and granulocytes. Agranulocytes have two varieties including, lymphocytes, macrophages, and monocytes. These cells are present in a large number of white blood cells. 

These fish lymphocytes have their roles in immunity and protecting fish from several diseases. The granulocytes contain other cells that are responsible for fighting pathogens and other harmful substances in the body.

Do fish have blood vessels?

Vessels are part of the circulatory system of fish. Arteries, veins, and capillaries are the vessels in fish that carry blood throughout their body.

All these vessels have elasticity and resistance that helps control the blood flow and blood distribution in the body cells.

Circulation of blood in fish

Unlike humans, fish do not have a heart with four chambers, and their heart consists of one atrium and one ventricle.

The circulation is single-loop circulation that means impure blood will pass through the heart and move into gills to become pure and oxygen-rich. From gills, it circulates throughout the body.

The blood is the medium of transporting numerous compounds to the body, and it has several constituents that make up the blood.

Like other organisms, it contains plasma and serum that contains many essential compounds such as water, proteins, and other solutes. Blood carries several electrolytes such as sodium, potassium, calcium, and others, which are necessary to maintain body mechanisms.

Several nutrients and gases are also present in the blood with other regulatory and immunological factors. All these constituents are necessary to maintain the biological processes in fish. Certain enzymes, hormones, and nitrogen substances also make up a percentage of blood.

Functions of blood in fish

Blood is the necessary component of a fish body, which performs multiple functions in their body. They are:

The role of blood is to supply oxygen to every cell of the body through a circulation pattern as the oxygen is crucial for fish survival.

It helps eliminate all the waste in the fish body, such as urea, ammonia, carbon dioxide, and others, taking them to the gills.

It supplies all the nutrients to the body’s cells that come in blood from ingesting food.

Blood containing hormones, electrolytes, and immunological factors blood plays a role in several necessary processes such as immunity, growth.

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