One of the most essential organs of the human body is the heart, along with all the other parts of the circulatory system. The heart pumps oxygen-filled blood and nutrients to the different parts of the body, then back to the heart, and the cycle repeats [1].
Given that we know the importance of the human heart, it is safe to ask if insects, like bees, also have a heart, how it is different from ours, and how does it function?
Bees have a heart, which is part of their open circulatory system. Unlike the human circulatory system, where blood is transported and restricted inside the veins and arteries, the bee’s circulatory system doesn’t have boundaries. Their “blood,” called hemolymph, flows freely inside their body cavity through their heart (or hearts) from the abdomen to their head [2] [3]. Then the cycle will repeat again.
Now, let us learn more about the bee’s heart and how it functions.
What is the function of the circulatory system?
Before we can fully understand the function of the bee’s hearts, it would be easier if we could compare and contrast our own heart’s role to that of an insect. So, what is the function of the heart, and what does it do for our body?
The human heart is a part of the closed circulatory system (also known as the cardiovascular system), which is an organ used to pump blood that carries oxygen and nutrients throughout the body through a series of networks of blood vessels, such as the veins and arteries.
It also removes the body’s waste from other internal organs, like carbon dioxide and other chemical byproducts.
If the human heart has a closed circulatory system, its main difference from that of insects, like bees’ circulatory system, is that insects have an open circulatory system, where there are no blood vessels carrying the bee’s blood throughout their body. Their heart also functions differently from ours.
To continue learning about bees, you should take a look at Can you eat bees?
Do bees have blood?
Aside from the heart and the blood vessels, the blood is also a part of the closed circulatory system. But for, the bees, their open circulatory system have different components.
Technically, bees’ blood is not really blood since it does not contain hemoglobin or red blood cells, which gives it a red color. What they have is a fluid (or goo) called hemolymph, which is also considered “bee blood.”
So, instead of red-colored blood, bees have a transparent or light yellowish color of hemolymph, which serves almost a similar purpose, which is to transport nutrients throughout the body and remove waste products.
It is also important to note that the term blood is generally used for vertebrates, while the hemolymph is for insects like bees. The hemolymph also represents 25 to 30% of the bee’s overall body weight [4].
The composition of blood and hemolymph are also different. Blood contains plasma (contains water, proteins, salts, and others), red and white blood cells, and platelets. On the other hand, hemolymph is made up of water, ions, carbohydrates, hormones, and others. The hemolymph can directly contact the tissues in the body cavity [6].
Another difference between blood and hemolymph is, unlike blood, hemolymph does not transport oxygen throughout the bee’s body. Instead, bees have air openings called spiracles, trachea, and trachea sacs that perform the function of transporting oxygen within their body cavity.
After you’re done with this article, you should also read How many bees are in a nuc?
What is the difference between a closed and open circulatory system?
The closed and open circulatory systems will differ mainly if the blood or hemolymph (for insects) are contained inside a vessel that transports the nutrient-filled blood through the body.
The closed and open circulatory system has a way for the blood or hemolymph to return to the starting point to continuously repeat the process in the body.
Suppose a circulatory system is closed, like for humans. In that case, blood vessels, particularly the veins and arteries, run throughout the body to carry the oxygen-filled blood up to the brain and down to the extremities. The heart is the main organ for a closed circulatory system, which pumps blood.
On the other hand, the open circulatory system doesn’t have blood vessels. Instead, they have a singular vessel (more like a tube) running throughout their body cavity. It starts from the abdomen, through the thorax, and into the head. This vessel transports hemolymph throughout the body.
Do bees have hearts?
Bees have an open circulatory system, meaning they don’t have any veins and arteries to carry or guide the blood throughout their bodies. Instead, their blood (called hemolymph) is not guided by blood vessels and travels freely throughout their body cavity [5].
Instead of an independent organ, the bee’s heart is like a long tube or vessel running from its abdomen, thorax, and head that carries the hemolymph throughout its body. The part of the heart located at the abdomen is called a dorsal heart, and the part running through the thorax is called the dorsal aorta.
The dorsal heart also has small openings on its sides called ostia that pulls the hemolymph into the vessel and into the bee’s body for circulation. Once the hemolymph reaches the head, it circles back to the thorax and back to the abdomen, where the cycle will repeat again.
The hemolymph that their heart pumps don’t carry oxygen. Instead, it has nutrients and hormones for the other body parts of the bee. The hemolymph also collects the waste generated in the body and transports it for excretion out of the rectum.
If you’d like to learn more about bees, you should also read Why do bees kill their queen?
Do bees have a single heart or multiple hearts?
Another interesting thing about the heart of a bee is that it is not just a single organ that pumps blood through blood vessels. Instead, bees have a series of them. We already learned that the bee’s heart is like a long tubular vessel that extends from the abdomen to the head.
This tubular vessel is composed of several muscle cells, like multiple hearts, that work together to pump the hemolymph throughout its body. The pumping of the muscle cells of their long heart allows the circulation of the hemolymph to happen.
What is the heart rate of bees?
The heart rate is a measure of the heartbeat, which are the number of contractions of the heart. It is commonly measured in terms of beats per minute or BPM [7].
For humans, an adult’s normal resting heart rate ranges from 60 to 100 beats per minute. But this number can be much lower for elite athletes like Usain Bolt, who has an extremely low resting heart rate of 33 BPM. If you want to get your maximum heart rate, you can subtract your age from 220.
Looking at the numbers, the human heart rate will almost be comparable to how fast bees’ hearts beat though they are probably more active. Bees are hard workers (only the female bees). They typically fly 15 miles per hour (24 kilometers per hour), and their wings can beat at a speed of 12,000 beats per minute (200 beats per second).
With the incredible speed of their movements, it is easy to assume that they have a faster heartbeat. However, though the number is inconclusive for their heartbeats, insects’ heart contraction rate only ranges from 30 to 200 beats per minute, depending on the species [8] – almost identical to humans.
I would also recommend reading our articles on the topics Do bees have bones? and Can a dead bee sting you?
Conclusion
Like other insects, the circulatory system of bees is an open circulatory system instead of the closed circulatory system that humans and vertebrates have. This means that they don’t have blood vessels, like veins and arteries, that carry blood throughout the body.
Bees also don’t have blood, in the same sense as ours, because it does not have red blood cells. Instead, they have hemolymph, a colorless fluid that is pumped by the heart and carries the nutrients throughout their body, and transports body waste to be excreted.
Since bees have an open circulatory system, their heart is like a long tube traveling from their abdomen to the thorax and the head. Their heart can also be considered multiple hearts since it has several muscle cells that extend throughout the body and pumps rhythmically.
References
[1] – Cleveland Clinic – Circulatory System,
https://my.clevelandclinic.org/health/body/21775-circulatory-system
[2] – Arizona State University – School of Life Sciences,
https://askabiologist.asu.edu/honey-bee-anatomy
[3] – Michel, J. (2019). Honey bee hearts. Proceedings (Baylor University. Medical Center), 32(1), 154-155. https://doi.org/10.1080/08998280.2018.1509578
[4] – Feng, M., Ramadan, H., Han, B., Fang, Y., & Li, J. (2014). Hemolymph proteome changes during worker brood development match the biological divergences between western honey bees (Apis mellifera) and eastern honey bees (Apis cerana). BMC Genomics, 15(1). https://doi.org/10.1186/1471-2164-15-563
[5] – American Bee Journal – The Internal Anatomy of the Honey Bee,
https://americanbeejournal.com/the-internal-anatomy-of-the-honey-bee/
[6] – Difference Between Blood and Hemolymph,
https://www.differencebetween.com/difference-between-blood-and-hemolymph
[7] – Wikipedia – Heart Rate,
https://en.wikipedia.org/wiki/Heart_rate
[8] – North Carolina State University – Agricultural and Life Sciences,
https://genent.cals.ncsu.edu/bug-bytes/circulatory-system/
