Do Insects Have Hearts?

A significant difference between insects and humans lies in their circulatory systems. Unlike humans, insects do not have lungs. But do they have a heart?

Insects do have hearts. For insects, the heart acts as a pump, pushing hemolymph throughout the circulatory system. The presence of hemolymph is one of the major differences between the insect and vertebrate circulatory systems.

This article will explore the intricacies of an insects’ circulatory system when compared to that of vertebrates’. Additionally, the similarities and differences between the hearts of insects and humans will be thoroughly explained.

Structure of the Insect Heart

Located in the abdomen of each insect lies a fragile organ surrounded by a membrane. This organ is known as the dorsal vessel, and it acts as the heart. The dorsal vessel is divided into separate chambers, each of which is broken up by valves. The valves directly control the flow of hemolymph as it travels toward the insect’s head from the dorsal vessel and vice versa.

At the frontal region of the heart lies a tube that is known as the aorta, which stretches toward the brain of the insect. This section of the heart lacks muscle and valves. Upon emerging from the aorta, the hemolymph coats the vital organs, muscles, and tissue of the cranial region.

Throughout the insects’ body cavity, there are pulsatile organs. These organs are not constantly in action. The pulsatile organs will jump into action in conjunction with other body organs to ensure that certain body movements properly push hemolymph out toward the extremities. Typically, these organs can be found toward the base of each wing or leg. 

Around 90% of an insect’s body consists of plasma. Plasma can be defined as a liquid, typically clear, yellow, or green in coloration. Plasma contains a relatively high concentration of amino acids when compared to the blood of vertebrates. In addition to amino acids, the plasma is capable of carrying high concentrations of essential supplies such as proteins, ions, and sugars. 

insect anatomy diagram
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What Is Hemolymph?

Hemolymph is a type of blood that flows freely throughout the body cavity of an insect. Similar to the way that humans require a constant supply of food, water, oxygen, and blood, insects require a constant supply of hemolymph.

The constant need for a supply of hemolymph lies in the fact that it contains and transports a number of items that are vital to the insect’s survival. These items include:

  • Hormones
  • Salts
  • Nutrients
  • Metabolic Wastes

Why Do Insects Need Hemolymph?

All of the items mentioned in the section above are crucial to an insect’s survival, thus the necessity of constant flow of hemolymph throughout the insect’s body cavity. Hemolymph helps the insects’ body to maintain its shape.

The constant supply of oxygen combined with regular blood flow ensures that the insect will be completely capable of regular mobility. Mobility, of course, is yet another trait that is necessary for the survival of the insect. For example, in the instance that an insect would need to flee from predators or launch itself toward its prey, it would be relatively seamless, assuming that proper regulation of the hemolymph is present. 

Another reason for the necessity of regulation within the circulatory system involves the immune system that exists within the insect—hemolymph aids in protection from internal parasites as well as invasive bacteria. 

Other notable processes that occur seamlessly as a result of the constant circulation of hemolymph include reproduction, molting, and egg hatching. 

Regular circulation of blood, oxygen as well as other nutrients is crucial to the survival of countless species worldwide. In insects, hemolymph is circulated throughout the entire body cavity in order to ensure that processes like reproduction, molting, and motion are able to take place.

Insect Circulatory Systems

While some of the genes that determine the development of the heart are similar in both vertebrates and insects, one of the main differences involves the makeup of the circulatory system as a whole. 

The layout of the insects’ circulatory system is entirely open in nature. This is something that is very common among arthropods. The majority of the insects’ body cavity is filled with fluids, including hemolymph. Hemolymph is the same clear, yellow, or green fluid that can be seen escaping the body of an insect that has been stepped on. 

Additionally, a very important vessel can be found along the inside of the insects’ body cavity. This vessel is used to move hemolymph throughout the insects’ body and is located toward the lower abdomen of the insect.

One trait that vertebrates and insects both possess is a heart, the primary organ at the center of the circulatory system in both types of living creatures. The heart can be found within the dorsal vessel. The insects’ heart contains small openings that permit the entrance and exit of hemolymph. 

When the heart is relaxed, the entrance of the hemolymph is permitted. The hemolymph is then pumped from the abdomen region toward the head of the insect. Once the hemolymph reaches the insect’s head, it immediately begins its journey back through the body cavity. 

The primary reasoning for the hemolymph to constantly cycle through relates to the fact that it comes in contact with all organs and tissue in order to supply it with necessary levels of blood and oxygen. 

Thin sheets of muscle and membrane separate each region of the body cavity from one another. The three resulting regions are known as the blood sinuses. These compartments work in unison to ensure that the heart contracts at a regular rate. The temperature of the outside environment is a key factor that influences the rate at which the heart will contract.

Vertebrate Circulatory Systems

For vertebrates, their circulatory systems fall under the category of a closed system. A closed system includes a system of veins and arteries that are used to transport blood throughout the body. In humans, the closed system has a heart and lungs at its center with a network of veins and arteries that work to transport oxygen and blood to and from the heart and lungs.

While vertebrate circulatory systems vary little from one species to another, the environment in which a species inhabits plays a major role in any evolutionary variations that may be present. For example, whether a vertebra lives on land or underwater has determined over years of evolution the exact makeup of the circulatory system. 

The heart of each vertebra lies in the front, central region of the chest just below the alimentary canal. It is common for the position of the heart to shift, even slightly, as the animal grows and develops.

The heart is an entirely muscular organ. This organ automatically beats to its own rhythm. Veins continuously deliver deoxygenated blood to the heart while the arteries deliver oxygenated blood away from the heart. Despite the number of anatomical differences, the circulatory systems of both insects and vertebrates alike serve nearly identical functions.

Conclusion

Insects do have hearts. The remainder of the insect’s circulatory system, however, varies drastically from the makeup of the vertebrate circulatory system. 

Though insects have a circulatory system that is entirely unique to the species, essential proteins, amino acids, and sugars are still constantly throughout the internal body cavity. To summarize, the heart is a vital organ that is crucial to the survival of every insect.

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