Circulatory System of a Squid

Circulatory System of a Squid
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  • 0:00 Classified: Mollusks
  • 0:55 Closed for Circulation
  • 2:02 Squid Blood
  • 2:29 Lesson Summary
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Lesson Transcript
Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

The squid is a unique aquatic mollusk with three hearts! Complete this lesson to learn what makes a squid stand out, and why it needs so many hearts to function efficiently.

Classified: Mollusks

A squid is a type of mollusk that has a long, soft body, tentacles, and arms that lives in oceans all around the world. Other animals classified as Mollusks include octopuses, snails, slugs, and clams, among others. Believe it or not, there are over 300 species of squid. They are characterized by a head, a mantle, arms, and bilateral symmetry. Squids come in a range of body sizes. They've been recorded to be a as small as a few inches to as long as 59 feet. Because they are aquatic species, squids breathe through the use of gills instead of lungs. Squids are also notorious for being excellent predators - they use jet propulsion moving in burst - to go after prey, which can include fish and even other squid.

Closed for Circulation

What kind of circulatory system satisfies such a vast size range? Squids, like humans, have a closed circulatory system, meaning all of their blood is contained in a network of blood vessels (arteries, veins, and capillaries). As you can imagine, it can take a lot of work to keep blood flowing throughout these organisms, but this is aided by the help of three hearts!

Of the squid's three hearts, two of them are located at the base of the gills. These are called brachial hearts. The brachial hearts pump deoxygenated blood back to the gills so carbon dioxide can be expelled and oxygen absorbed from the surrounding water. Once the blood has been re-oxygenated, a centrally located systemic heart pumps the oxygenated blood to the rest of the body. Then, oxygen and nutrients are delivered to the tissues, and carbon dioxide and waste materials are picked up to be removed from the body. The brachial hearts then pump this blood back to the gills, and the system repeats itself. Remember, blood is contained in the blood vessels throughout this entire process.

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