Squid can ‘drop arms’ as defensive tactic

August 3rd, 2012 - 3:28 pm ICT by IANS  

Washington, Aug 3 (IANS) A small species of deep-sea squid can detach the tips of its arms when under attack, leaving them fastened on its predator as a distraction, says a study.

Stephanie Bush, post-doctoral researcher at the University of Rhode Island, said that when the foot-long octopus squid found deep in the northeast Pacific Ocean “jettisons its arms” in self-defence, the bioluminescent tips continue to twitch and glow, creating a diversion that enables the squid to escape from predators.

“If a predator is trying to attack them, they may dig the hooks on their arms into the predator’s skin. Then the squid jets away and leaves its arm tips stuck to the predator,” explained Bush. “The wriggling, bio-luminescing arms might give the predator pause enough to allow the squid to get away.”

While Bush was a graduate researcher working with the Midwater Ecology Lab at the Monterey Bay Aquarium Research Institute, she observed that many octopus squid had arms of different lengths, the journal Marine Ecology Progress Series reported.

Scientists had speculated that they may release their arms, just as lizards can release their tails when attacked, but no one had seen it happen. Using a remotely operated vehicle in the Monterey Bay Submarine Canyon off the coast of California, Bush poked at a squid with a bottlebrush, according to a statement of Midwater Ecology Lab.

“The very first time we tried it, the squid spread its arms wide and it was lighting up like fireworks,” she said. “It then came forward and grabbed the bottlebrush and jetted backwards, leaving two arms on the bottlebrush. We think the hooks on its arms latched onto the bristles of the brush, and that was enough for the arms to just pop off.”

In further experiments, Bush found that some octopus squid appeared hesitant to sacrifice their limbs, but some did so after being prodded several times. When she provoked seven other squid species similarly, none dropped their arm tips. The squid are able to re-grow their missing arms.

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