Deep-sea squids' tentacle tips swim on their own

This is a Grimalditeuthis bonplandi squid with one of its tentacles extended. The arrow points to a small "club" at the end of the tentacle that wiggles and appears to swim independently of the rest of the animal.
2005 MBARI

Like something straight out of a sci-fi film, scientists have discovered that the tips of a deep-sea squid's tentacles 'swim' on their own. The tips, called clubs, sit at the end of long feeding tentacles.

Most squids use their feeding tentacles to capture prey. But the Grimalditeuthis bonplandi squid has long, thin, fragile tentacles that are not strong enough for the job. The weak tentacles lack usual tools like suckers, hooks and glowing spots. And so, the tips of their tentacles adapted to seemingly swim on their own.

"In short, all of the motions and activities of these squids appear to be directed toward giving the impression that their clubs are small, swimming animals, independent from the rest of the squids' bodies," the Monterey Bay Aquarium Research Institute (MBARI) scientists wrote in a press release.

Using underwater, remote-controlled cameras (ROVs), the study authors observed the squids' behavior in their natural setting: some 1,000 to 2,000 meters undersea in the Monterey Bay and the Gulf of Mexico. They also dissected the remains of more than 20 squid.

The videos showed that the clubs started to swim on their own in a fluttering and flapping motion propelled by thin, fin-like membranes on the clubs. The tentacles trailed behind.

The clubs don't actually have a mind of their own. The squid is sending the clubs swimming away from its body, as the tentacles trail behind. As the tentacles are fully extended, the clubs continue to wiggle about.

In addition to this unique style of capturing prey, the G. bonplandi reacts differently when it perceives a threat. Rather than gathering its tentacles in, the squid swims to the clubs, then coils its tentacles and clubs and tucks them into its eight arms. Once everything is tucked away, the squid swims away from the threat.

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    Danielle Elliot is a freelance science editor and reporter for CBS News. She holds an M.A. in science and health journalism from Columbia University and a B.A. in broadcast journalism from the University of Maryland. Follow her on Twitter - @daniellelliot.