How many hearts does an octopus have? and why is it three?

How many hearts does an octopus has? three. Photo of an octopus swimming underwater.

If you are here you are probably wondering: How many hearts does an octopus have? short answer: Three hearts. You might be wondering how is that even possible and why, in this blog post we explain all about it.

When it comes to the octopus, there’s more than meets the eye – or in this case, the tentacle. Beyond its interesting appearance and insane intelligence lies a biological wonder: three hearts. But what’s the practical significance of this anatomical quirk, and how does it impact the life of this species? Let’s dive in (ba dum tss).

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Within marine biology, few creatures provoke as much fascination and interest as the octopus. These cephalopods, stand as both subjects of normal human curiosity and professional scientific intrigue.

Despite their seemingly alien features, octopuses are finely tuned to their marine environment. Showcasing keen senses, complex behaviors, and unparalleled problem-solving abilities. Their capacity to change color and texture for camouflage, coupled with their adeptness at navigating difficult underwater landscapes, speaks to their evolutionary experience.

One aspect of octopus physiology remains intriguing: their cardiovascular system. This anatomically different system gives insight into their unique physiological adaptations to life beneath the water.

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How Many Hearts Does an Octopus Have: The Details

How many hearts does an octopus have? three. As you can see in this anatomy diagram showing the three hearts inside an octopus. Figure 3.12 from Wells, M. J. (1978). Octopus: Physiology and Behaviour of an Advanced Invertebrate. Chapman & Hall. p.42
Anatomy diagram showing the three hearts inside an octopus (the ones the arrows are pointing to).
Figure from Wells, M. J. (1978). Octopus: Physiology and Behaviour of an Advanced Invertebrate. Chapman & Hall. p.42

Octopuses possess not one, not two, but three hearts. Two of these hearts, known as branchial hearts, handle the task of pumping blood to the gills. Here, oxygen is absorbed from the surrounding water, providing the octopus with the fuel it needs to keep moving. Once oxygenated, the blood is shuttled to the third heart, the systemic heart, which distributes it throughout the body, ensuring every cell gets its share.

How many hearts does an octopus has? three. Photo of an octopus underwater attached to a rock.
Photo by yu zhang via Pexels.

Why Do Octopuses Have Three Hearts?

The presence of three hearts in octopuses is not merely a quirk of evolution. It’s a strategic adaptation to their environment and physiology. Octopuses have blue blood, thanks to a copper-based protein called hemocyanin, which is less efficient at transporting oxygen compared to the iron-rich hemoglobin found in vertebrates. To compensate for this inefficiency, octopuses have evolved three hearts. Two branchial hearts pump blood to the gills for oxygenation, while the third, central heart distributes oxygen-rich blood throughout the body. This elaborate cardiovascular system ensures that octopuses can thrive in environments with high oxygen levels and high metabolic demands.

How many hearts does an octopus has? three. Photo of an octopus underwater swimming showing its tentacles.
Photo by Ashley Christiano from Pexels

The three-heart system in octopuses allows them to maintain an active lifestyle and support their extensive nervous system. This adaptation is crucial for octopuses, which rely on quick movements and sharp senses to navigate their environment and hunt for prey.

10 Facts About Octopus Hearts

10 Facts About Octopus Hearts. Photo of an octopus underwater attached to a rock.
Photo by Pia B via Pexels

As we know, octopuses have three hearts, but that isn’t the only fascinating thing about their cardiovascular system. Below we give you 10 interesting facts about octopus hearts that you won’t find on any other page.

These facts are constructed from the information found in the book Octopus: Physiology and Behaviour of an Advanced Invertebrate by M. J. Wells.

1. Adaptive Responses to Stress

In response to environmental stressors, such as oxygen deprivation or confined spaces, octopus hearts demonstrate a remarkable ability to modulate stroke volume rather than altering frequency. Which optimizes blood flow to sustain vital functions.

2. Oxygen Sensitivity

Octopus heartbeats serve as sensitive indicators of oxygen availability, slowing dramatically in oxygen-deprived conditions. Showcasing the critical importance of oxygen in cephalopod physiology.

3. Nervous Regulation

Octopuses’s heartbeats involve a complex interplay of neural signals. With branches from visceral nerves exerting regulatory control over cardiac activity. These nerves receive input from various physiological systems within the octopus’s body, including sensory feedback from the heart itself and other organs like the gills. This integration of sensory information allows for precise adjustments in heart rate and rhythm in response to changes in oxygen levels, carbon dioxide concentrations, or other metabolic factors. Through this neural network, the octopus’s cardiovascular system remains finely tuned to meet the demands of its marine environment. Ensuring efficient circulation and oxygen delivery throughout their body.

Anatomy diagram of the respiration circulation and excretion of an octopus. The visceral nerve is highlighted. As octopus heartbeats involve a complex interplay of neural signals. With branches from visceral nerves exerting regulatory control over cardiac activity. These nerves receive input from various physiological systems within the octopus's body, including sensory feedback from the heart itself and other organs like the gills. This integration of sensory information allows for precise adjustments in heart rate and rhythm in response to changes in oxygen levels, carbon dioxide concentrations, or other metabolic factors. Through this neural network, the octopus's cardiovascular system remains finely tuned to meet the demands of its marine environment. Ensuring efficient circulation and oxygen delivery throughout their body.
The placement of the visceral nerve is highlighted in this anatomy diagram of the respiration circulation and excretion of an octopus.
Figure from Wells, M. J. (1978). Octopus: Physiology and Behaviour of an Advanced Invertebrate. Chapman & Hall. p.41

4. Carbon Dioxide Transport

Octopus blood exhibits a high efficiency in removing carbon dioxide, mirroring the capability observed in crustacean blood. This characteristic is fundamental for maintaining acid-base equilibrium and facilitating gas exchange within their marine ecosystem. By efficiently eliminating carbon dioxide, octopus blood ensures that metabolic processes remain balanced and that adequate oxygen levels are maintained, thereby supporting the organism’s physiological functions in its habitat.

5. Hemocyanin Composition

Octopus blood relies on the protein hemocyanin for efficient oxygen transport, with its ability to bind oxygen rapidly and facilitate gas exchange crucial for sustaining life in the marine environment.

6. Synthesis in Branchial Glands

Hemocyanin synthesis occurs predominantly in the branchial glands, located beneath the gills in octopuses. These glands contain cells filled with organized structures called endoplasmic reticulum, along with vacuoles. Within these cells, hemocyanin particles are abundant, which is what indicates that the branchial glands are where hemocyanin is made. This process ensures a steady supply this vital oxygen carrier in octopuses’ bodies.

If the branchial glands are removed surgically,
or destroyed by freezing, no labelled haemocyanin is made, and the
animals die within a few days.

Wells, M. J. (1978). Octopus: Physiology and Behaviour of an Advanced Invertebrate. Chapman & Hall. p.49
An anatomy figure of an octopus. Placement of the branchial glands highlighted. Hemocyanin synthesis occurs predominantly in the branchial glands, located beneath the gills in octopuses. Octopus blood relies on the protein hemocyanin for efficient oxygen transport, with its ability to bind oxygen rapidly and facilitate gas exchange crucial for sustaining life in the marine environment.
Figure from Wells, M. J. (1978). Octopus: Physiology and Behaviour of an Advanced Invertebrate. Chapman & Hall. p.22

7. Bohr Effect

Octopus hemocyanin exhibits a marked Bohr effect. Enhancing oxygen release in tissues with decreased pH. This is a physiological adaptation essential for meeting metabolic demands during periods of heightened activity.

8. Terminal Respiration

During terminal respiration, octopus cells undergo a transition in oxygen uptake mechanisms, shifting from copper-based to iron-based pigments. This transition is facilitated by molecules known as cytochromes and flavins, crucial for cellular respiration. Studies have shown that these molecules in octopus tissues bear striking similarities to those found in mammalian tissues.

Terminal respiration refers to the final stage of the respiratory process within cells, where oxygen is utilized for energy production through a series of biochemical reactions. In this phase, oxygen serves as the terminal electron acceptor in the electron transport chain, ultimately leading to the generation of ATP, the cell’s primary energy currency. Terminal respiration typically occurs in specialized cellular structures called mitochondria, where enzymes such as cytochromes and flavins play crucial roles in facilitating the transfer of electrons and the production of ATP. This process is essential for powering various cellular activities and maintaining the overall metabolic functions of the organism.

9. Phagocytic Blood Cells

Octopus blood contains amoebocytes, which aid in phagocytosis and blood clotting, contributing to wound healing and immune responses, essential for maintaining health and vitality.

10. Environmental adaptation

The rare cardiovascular system of octopuses showcases their adaptation to the oceanic environment. Highlighting their vulnerability to environmental changes, such as rising ocean temperatures and increasing acidity levels.

Conclusion

In conclusion, the three hearts of the octopus are not just a biological curiosity; they are a testament to the incredible adaptations that enable octopuses to thrive in the depths of the ocean.

We hope that understanding the intricacies of octopus physiology deepens your appreciation for this incredible species. We also hope that this appreciation makes you think twice the next time someone offers you to eat such intelligent and complex creatures.

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