Octopuses are captivating marine creatures known for their intelligence and unique biological features. These invertebrates display complex behaviors, from solving puzzles to camouflaging with precision. Their adaptations extend to their internal anatomy, particularly their circulatory system, which differs significantly from many other animals. This system allows them to thrive in diverse ocean environments, supporting their active, predatory lives.
More Than One Heart
Octopuses possess a distinctive circulatory system featuring three hearts. This arrangement is a defining characteristic of all known octopus species. Two of these hearts are known as branchial hearts, or gill hearts, situated near the gills within the mantle. The third heart, called the systemic heart, is positioned centrally within the octopus’s body. This largest and most muscular heart is crucial for circulating blood throughout the main body.
The placement of the branchial hearts at the base of each of the octopus’s two gills allows for a direct and efficient pathway for blood to pass through these respiratory organs. The centrally located systemic heart then effectively receives and distributes blood. This anatomical setup ensures that the circulatory system operates as a closed loop, similar to that of humans, where blood remains within a network of arteries and capillaries.
The Purpose of Each Heart
Each of the three hearts in an octopus performs a distinct role in its circulatory process. The two branchial hearts pump deoxygenated blood through the gills. As blood passes over gill filaments, it releases carbon dioxide and absorbs oxygen from the surrounding water. These hearts ensure efficient blood flow, maximizing oxygen uptake.
Once oxygenated, this blood flows to the single systemic heart. Its primary function is to receive oxygen-rich blood from the gills and pump it throughout the octopus’s body. This delivers oxygen and nutrients to muscles, organs, and the surprisingly large brain. This division of labor creates an efficient system.
How This System Benefits Octopuses
The octopus’s three-heart system provides advantages, supporting its active lifestyle and survival in challenging marine conditions. Their blood contains hemocyanin, a copper-based protein that turns blue when oxygenated, unlike the iron-based hemoglobin found in human blood. While hemocyanin is effective in cold, low-oxygen environments, it is less efficient at carrying oxygen than hemoglobin. The three hearts compensate by ensuring blood circulates quickly and at sufficient pressure to deliver oxygen throughout the body.
This circulatory system allows octopuses to maintain a high metabolic rate, which is necessary for their agility, intelligence, and predatory behaviors. The two branchial hearts reduce the workload on the systemic heart, allowing it to focus on distributing oxygenated blood. This is valuable because the systemic heart can temporarily slow or stop during strenuous activities like jet propulsion, making crawling a more energy-efficient mode of movement.