How Many Hearts Does An Earthworm Have

There is no straight forward answer to how many hearts does an earthworm have. An earthworm can be associated to have no heart or 10 pseudo hearts or aortic arches to be specific. The number 10 is not fixed it can vary among the Earthworm species. Biologist simply could not have the consensus whether to classify Aortic Arches as hearts or simply beating tubes.
In this post, we will see how an Earthworm heart works, where it is located and how temperature affects the hearts’ contribution to the soil fertility.


how many hearts earthworm have

Why Earthworm Needs Heart?

Earthworms have closed circulatory system and need some pumping mechanism to supply blood to its segmented body’s respiratory system, digestive system, nervous system, and reproductive system. The closed circulatory system means the vessels carrying blood are in the closed circular path just like human beings.

How Earthworm Heart Works

Heart Location and Physical Structure

Aortic arches act like the valves in the human heart. Just below the brain, the aortic arches look like a coil network wrapped around the esophagus or food pipe of the earthworm. Aortic arches or Pseudo hearts are large muscular tubes and supply blood via alternate contraction and relaxation.
An interesting thing to note that the portion where the arches connect each other is quite thick and is often regarded as the main heart stem of the earthworm while aortic arches as subsidiary pumping tubular structures.

Earthworm Vessel Network

The blood to different organ systems is carried via vessels. These vessels are the aortic arches, dorsal blood vessels, and ventral blood vessels. Dorsal blood vessels are darker than the ventral vessels. They appear as dark brownish red vessels along the intestine.

how many hearts earthworm have

Heart As Bridge

The two vessels system dorsal and ventral are connected with each other via aortic arches. Blood flows from the dorsal vessel system to the aortic arches which pump or beats the blood into the ventral vessels. Dorsal vessel system is responsible for supplying blood to the front body part of the earthworm while the ventral supplies blood to the back.

Heart As Supplier of Oxygen

As the earthworm moves through the moist soil it grabs the air from the moisture through its respiratory skin and processes it into the circulatory system through the blood vessels.

The blood in the earthworm gets pumped via heart or aortic arches. Blood contains the dissolved oxygen and carbon dioxide. Oxygen is put into good use by the absorption of cellular activity while the carbon dioxide is released back into the soil through diffusion between earthworm’s skin and the soil.

An exciting fact the respiratory system of earthworm consists of only its skin.

Earthworm Hearts and Temperature?

These annelids are cold-blooded and yes the earthworm’s aortic arches do beat and its been observed through experiment that the amount of beats increases with increase in temperature.

At below room temperature, the pulse rate is 14 pulses per minute.

At room temperature, the pulses were observed at 30 pulses in a minute.

At higher temperature like placed in hot in the jacuzzi, the worm had 44 pulses per minute which is quite high. So the worm circulatory system works faster at a higher temperature.

In winter the aortic arches or worm’s heart due to frozen ground works lesser by beating less. This helps the worm to conserve energy and survive through the difficult weather by conserving its energy.

The converse also happens during summer the pulse rate becomes higher and the worm needs more energy. This means it becomes more active and hungry. More activity helps in more burrowing of the soil. So the faster circulatory system is beneficial for the soil fertility.

Earthworm’s Dual Purpose Heart Pumping

The circulatory system comprising of three vessel system does the job for both food allocation, waste excretion and also to provide the gases at the cellular level to generate energy.

The blood carries hemoglobin giving it distinct red color along with the amoebic cell contracted via soil moisture.

Why Do EarthWorms Have 5 Pair Hearts

Depending upon the species earthworms can grow up to 3 meters long. That is quite long for one muscular tube to pump the blood to the farthest point of the body.

Consider the hearts location it is located in the very upper region of the earthworm.
And it’s not really as sophisticated as mammals heart, aortic arches are simply muscles contracting and relaxing with rhythm. So it is a necessity for an earthworm to have the pairs of arches typically around 5 so it can pump from head to the final segment along the complete length of the body.

If it had one aortic arch maybe it would have not survived as a species. Biologists argue that the development of pairs of pseudohearts has been the result of millions of years of evolution in this simple annelid that it can survive under such massive pressure of the soil.

CONCLUSION: How Many Hearts Does An Earthworm Have

To conclude “how many hearts does an earthworm have” we reach the point that it is an integral requirement for the worm to have a large number of hearts to cater the absence of a sophisticated heart like that of mammals. Although it seems like the creature is the missing heart but in reality it pseudo heart is carrying out all the complicated tasks of a mammal heart.


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