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Blue Bloods

Short answer: Squid, like octopuses and cuttlefish, have three hearts: two branchial hearts pump blood through the gills, and a systemic heart pumps it around the body.

Their blood is blue when oxygenated because it uses hemocyanin, a copper-containing protein, to carry oxygen, instead of the iron-based hemoglobin in human red blood cells. Hemocyanin is dissolved in the blood rather than packed into cells. The footage shows squid swimming, with the presenter.

VideoWrite-up2 sources
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What should you know about Blue Bloods?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. Squid have three hearts.

    DD-193-F01 · Write-up · Exhibit A (Three hearts)

  2. Two hearts pump blood to the gills.

    DD-193-F02 · Write-up · Exhibit B (Gill hearts)

Video transcript: Blue Bloods: Squid Have Three Hearts and Blue Blood

Squid have three hearts and blue blood. Two of the hearts pump blood to the gills, while the third pumps it to the rest of the body. DID YOU KNOW? The blue color of their blood comes from a copper-based molecule called hemocyanin, which is used to transport oxygen. This is different from humans, whose blood is iron-based and red when oxygenated. NOW YOU KNOW!

Burned-in captions, read frame by frame (see transcript.md) · 17.2s Reel ·

Video coming soonBlue Bloods · Instagram Reel
Blue Bloods: Squid Have Three Hearts and Blue Blood Instagram Reel · · 17.2s

The write-up

Squid have three hearts and blue blood. Copper-based hemocyanin carries their oxygen.

  1. Exhibit A

    Three hearts

    Squid have three hearts.

  2. Exhibit B

    Gill hearts

    Two hearts pump blood to the gills.

  3. Exhibit C

    Systemic heart

    One heart supplies the body.

  4. Exhibit D

    Hemocyanin

    Copper-based hemocyanin carries oxygen.

  5. Exhibit E

    Blue color

    Oxygenated hemocyanin is blue.

Questions people ask about Blue Bloods

How many hearts does a squid have?

Like octopuses.

Source: Write-up · Exhibit A (Three hearts) · Wikipedia: Squid

What do two of them pump to?

Branchial hearts.

Source: Write-up · Exhibit B (Gill hearts) · Wikipedia: Squid

What carries oxygen in squid blood?

Copper-based.

Source: Write-up · Exhibit C (Systemic heart) · Wikipedia: Squid

What color is it when oxygenated?

Hence the title.

Source: Write-up · Exhibit D (Hemocyanin) · Wikipedia: Hemocyanin

Which metal is in human hemoglobin?

Red blood.

Source: Write-up · Exhibit E (Blue color) · Wikipedia: Hemocyanin

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. How many hearts does a squid have?

    1. Three
    2. One
    3. Two
    4. Eight
    Show the answer

    Answer: A. Three Like octopuses. Source: Write-up · Exhibit A (Three hearts) · Wikipedia: Squid

  2. What do two of them pump to?

    1. The gills
    2. The brain only
    3. The ink sac
    4. The tentacles only
    Show the answer

    Answer: A. The gills Branchial hearts. Source: Write-up · Exhibit B (Gill hearts) · Wikipedia: Squid

  3. What carries oxygen in squid blood?

    1. Hemocyanin
    2. Hemoglobin
    3. Chlorophyll
    4. Water
    Show the answer

    Answer: A. Hemocyanin Copper-based. Source: Write-up · Exhibit C (Systemic heart) · Wikipedia: Squid

  4. What color is it when oxygenated?

    1. Blue
    2. Red
    3. Green
    4. Clear
    Show the answer

    Answer: A. Blue Hence the title. Source: Write-up · Exhibit D (Hemocyanin) · Wikipedia: Hemocyanin

  5. Which metal is in human hemoglobin?

    1. Iron
    2. Copper
    3. Zinc
    4. Gold
    Show the answer

    Answer: A. Iron Red blood. Source: Write-up · Exhibit E (Blue color) · Wikipedia: Hemocyanin

Cite this case file

Easterling, Marcus. "Blue Bloods." The Detail Department (DetailEnjoyer), case file DD-193, last updated Jan 21, 2024. https://detailenjoyer.com/case/blue-bloods/

Permalink: https://detailenjoyer.com/case/blue-bloods/ · Last updated

Markdown version

Cite a single fact by its ID, for example DD-193-F01 → https://detailenjoyer.com/case/blue-bloods/#DD-193-F01