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the claim

Octopuses have blue blood because of copper-based hemocyanin.

the verdict
SUPPORTED
the evidence backs this
Recorded sources
5 sources for · 0 against

Counts group repeated records of the same source within each side. They do not measure evidence strength or source independence.

Is it true that Octopuses have blue blood because of copper-based hemocyanin?

Yes. A National Geographic article states directly that several octopus species have blue blood and that the blue comes from a copper-rich protein called hemocyanin. Reference works on hemocyanin confirm it is a copper-based oxygen carrier that turns blue when oxygenated, though they do not name octopuses.

Verdict: SUPPORTED · 5 sources for, 0 against · Last checked

The private library was unavailable for some searches in this check. Missing library results are not evidence against the claim.

Evidence for · 5
Hemocyanin - Wikipedia
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Hemocyanin - Wikipedia. (n.d.). en.wikipedia.org. https://en.wikipedia.org/wiki/Hemocyanin

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More for · 4
Blue Blood
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Blue Blood. (n.d.). en.wikipedia.org. https://en.wikipedia.org/wiki/Blue_Blood

Hemocyanin: The Copper Blood
1976
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M., S. N. (1976). Hemocyanin: The Copper Blood. eric.ed.gov. https://eric.ed.gov/?id=EJ151877

In Animal Kingdom, Blood Comes in a Rainbow of Colors | National Geographic
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In Animal Kingdom, Blood Comes in a Rainbow of Colors | National Geographic. (n.d.). nationalgeographic.com. https://www.nationalgeographic.com/animals/article/150312-blood-antarctica-octopus-animals-science-colors

Dumbo Octopus and Other Strange Squid and Octopuses
2026
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Dumbo Octopus and Other Strange Squid and Octopuses. (2026). ebookcentral.proquest.com. https://ebookcentral.proquest.com/lib/kxp/detail.action?docID=32270104

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