Octopuses have 3 hearts, and 2 stop beating when they swim
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An octopus has one main heart (the systemic heart) that pumps blood to the body, and two branchial hearts that pump blood through each gill. When an octopus swims by jet propulsion, the branchial hearts stop contracting — which is why octopuses prefer crawling and tire quickly when swimming. Their blue blood contains copper-based hemocyanin instead of iron-based hemoglobin.
Most people don't know octopuses have three hearts, let alone that swimming literally stops two of them from beating.
The Science Behind It
An octopus has one main heart (the systemic heart) that pumps blood to the body, and two branchial hearts that pump blood through each gill. When an octopus swims by jet propulsion, the branchial hearts stop contracting — which is why octopuses prefer crawling and tire quickly when swimming. Their blue blood contains copper-based hemocyanin instead of iron-based hemoglobin.
Why Your Brain Finds This Hard to Believe
Sources & Verification
OddlyHuman Editors
VerifiedWritten and fact-checked by the OddlyHuman Behavioral Science Team. We verify all psychological, sociological, and historical claims against peer-reviewed journals, primary sources, and established encyclopedias to bring you accurate insights.
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