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When an octopus is swimming, the organ that delivers blood to the organs stops beating. Octopus blood is blue because it has a copper-based protein called hemocyanin. One pumps blood through its organs the two others pump blood through its gills, according to the World Animal Foundation. This shell loss likely helped the ancient relatives of today's octopus, squid and cuttlefish become more agile to evade predators and nab prey, the researchers said. A study published online Main the journal Proceedings of the Royal Society B: Biological Sciences revealed these marine animals lost their hard "mobile homes" in the Jurassic and Cretaceous periods. The ancestors of octopuses and squid sported hard shells. Octopuses weren't always squishy creatures. Octopuses have powerful jaws and venomous saliva, according to National Geographic. The only hard part of their bodies is a sharp, parrot-like beak that is on the underside, where the arms converge. In April 2016, an octopus at the National Aquarium of New Zealand squeezed out of its tank and made an eight-armed dash for a drainpipe that - luckily for him - led directly to the sea.Ī bulbous sack-like body, or mantle, is perched on top of an octopus' head. Their bodies are soft, enabling them to squeeze into small cracks and crevices, according to National Geographic. Most octopuses - those in the suborder Incirrata (or Incirrina) - have no internal skeletons or protective shells. Their suckers have receptors that enable an octopus to taste what it is touching. Octopuses have an excellent sense of touch, according to the World Animal Foundation.