Foot-long squids found deep in the northeast Pacific Ocean "jettisons its arms" in self-defense, reveals a recent research.
The never-seen-before defensive strategy of the deep-sea squid was first observed by Stephanie Bush, a postdoctoral aquatic researcher at the University of Rhode Island.
According to Bush, when the octopus squid (Octopoteuthis deletron) loses its arms in self-defense, the bioluminescent tips continue to glow and divert the predators giving the squid enough time to flee.
"If a predator is trying to attack them, they may dig the hooks on their arms into the predator's skin," said Bush. "Then the squid jets away and leaves its arm tips stuck to the predator. The wriggling, bioluminescing arms might give the predator pause enough to allow the squid to get away."
"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."
Bush also observed that the squids re-grow their missing arms.
"There is definitely an energy cost associated with this behavior, but the cost is less than being dead," Bush said.
Bush's started her studies on squids back in 2003 and she investigated the assumptions about deep-sea animals made by some scientists.
"Scientists had assumed that squid living in the deep-sea would not release ink as a defensive measure, but all the species I've observed did release ink," she said. "They assumed that because they're in the dark all day every day that they're not doing the same things that shallow water squids are doing. They also assumed that deep-sea squid don't change color because of the dark, but they do."
Bush has also studied the defense strategy of seven other species of squids and observed that none of them jettisoned their arms in self-defense.
The study was published in the July issue of the journal Marine Ecology Progress Series.
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