![]() ![]() ![]() Lizards are the most famous example – many of their can break off their tail if they are caught by a predator. Many animals can willingly amputate parts of their body. Instead, the squid only amputates what it has to. That’s very different to octopuses, which break off their arms at a pre-set point at their base. To minimise these costs, the squid practices what Bush calls “economy of autotomy” – it breaks off its arm just above the point where it has grabbed or been grabbed. In the meantime, the squid may have trouble grabbing food (especially since it possibly uses the glowing tips as fishing lures). The arms can grow back, but it takes a while to do so. Self-amputation seems like a rather drastic measure. This dramatic ability is just part of its defensive arsenal, which also include camouflage, jet-propulsion, ink, and its distracting light-producing arm tips. While some octopuses have the ability to break off their arms, O.deletron is the first squid that’s known to do so. I imagine it would be quite off-putting if you were a fish or a bottle brush. The arms flashed away while continuing to hold their grip, while the squids jetted off. Five of them broke off their arms while they were grabbing the brush. When Bush threatened the animals with a bottle brush, several of them attacked it. But it can also use this ability offensively. The obvious interpretation is that the squid jettisons its body parts to confuse and distract a predator. The glow is bright enough that Bush could see it under full laboratory lighting. Once broken, the tips flail about for at least 10 seconds, while glowing vigorously from the light-producing organs at their tips. Either the squid has to grab something, or something has to grab it. The breaks can happen at different points along the arm, but they always need some tension. “It grasped the textured bottom (rubber topped with fabric) of its holding container with the arm hooks, somersaulted, and re-leased ink as it autotomized part of all 8 arms.” One particular individual had a flair for theatrics: Back in the lab, 7 of the 11 captured squid did the same thing. Even while the sub was collecting specimens, one of the squids broke off two arms. These sightings suggested that the squid could willingly break off its arms, and Bush confirmed that ability when she brought some back to her lab. Fishermen have made similar reports they’ve caught O.deletron specimens with blunt-ended arms. And on a few dives, the vehicle saw disembodied tips, cleanly severed and slowly sinking. The squids normally have eight arms that taper to a point, but a quarter of the animals that Bush saw had at least one short, blunt-ended arm. She used remotely operated underwater vehicles to film 84 of them, and reviewed archival footage of 21 more individuals. Stephanie Bush from the Monterey Bay Aquarium Research Institute has been studying the squid for the last decade. ![]()
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