Why Octopus Arms Don’t Get Tangled Up

Common Octopus

Unlike humans, octopuses are not constantly aware of the location of their arms.  So with eight limbs in motion, it’s a wonder how their arms don’t get tangled up together.

According to researcher Guy Levy at the Hebrew University of Jerusalem, “We thought about it and we said, ‘How is it possible that the arms don’t grab each other?'”

Levy and his colleague Nir Nesher conducted a series of experiments with octopus arms. They observed that the suckers on the octopus arm would grab objects within its reach, but it would not grab anything with octopus skin. Their studies suggested that octopus skin has a repellent chemical. The sucker on an octopus arm can “taste” this repellent, so it does not grab on to it.

According to Roger Hanlon, of the Marine Biological Laboratory in Woods Hole, Massachusetts, “In fact, many of the sensory neurons known to occur in cephalopod suckers have unknown functions. The authors have widened our view of octopus sensory perception and provided some stimulating research questions to pursue.”

For more on this study, including a podcast, visit the NPR website.

To learn more fun facts about octopuses, see Animal Fact Guide’s common octopus facts page.

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Tiny Tyrannosaur Fossil Discovered in Alaska

A fossil of a small tyrannosaur that lived 70 million years ago was recently discovered in northern Alaska. The pygmy dinosaur, called Nanuqsaurus hoglundi (which means “polar bear lizard”), is believed to be a close relative of Tyrannosaurus Rex.

N. hoglundi was much smaller than the T. Rex. Its skull measures 25 inches as compared to the T. Rex‘s 60-inch skull.  Researchers have postulated that the pygmy tyrannosaur’s smaller stature was an adaptation to the cooler Arctic climate. Although the Arctic would have been much warmer in the Cretaceous Period than it is today, bouts of cold temperatures would have caused variations in the food supply.

Although N. hoglundi was only about half the size of the T. Rex, it still was an impressive 23 feet from head to tail.

Learn more at Discover Magazine and Smithsonian.

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