Nature is inspirational for many, including designers and innovators. You can thank geckos for surgical glue and express gratitude for burrs (yes, those pesky seeds!) when you Velcro a bag shut. We might be thanking octopuses next. Researchers are optimistic that knowing more about how they control their arms could help designers create soft-bodied robots.
Octopuses leverage all eight appendages to guide them through the water, sense their surroundings, and capture prey. Despite their impressive arm array, their movements can look awkward and seemingly unplanned at times.
“Normally when you look at an octopus for a short while, nothing is repeatable. They squirm around and just look weird in their exploratory movements,” says Trevor Wardill, an assistant professor of Ecology, Evolution, and Behavior who studies octopuses and other cephalopods, including cuttlefish and squid. Wardill and colleagues recently published their findings in Current Biology.
To study this, researchers dropped different types of prey, including crabs and shrimp, into the tanks with California twospot octopuses and recorded videos. The octopuses, who were hiding in ornamental SpongeBob Squarepants “dens” with one eye facing outward, lunged for the snacks.
How they lunged differed depending on whether it was a crab or shrimp. When hunting crabs, octopuses pounced on the prey with a cat-like movement. When hunting shrimp, the octopuses were more careful to avoid spooking the prey. They led with an arm and then used neighboring arms one and three to secure it.
No matter the prey though, the octopuses always lead the attack with the second arm from the middle, which is somewhat surprising given how awkward their movements often are. Additionally, the second arm on the right or left side was always the same side as the eye that first spotted the prey from the den.
Flavie Bidel, the lead author and a postdoctoral researcher in the lab, was shocked at how predictably octopuses began prey capture with the second arm. For creatures whose movement appears unpredictable, the hunting behavior was actually exceedingly repeatable. One of the next steps is to study how neurons facilitate arm movements.
“Octopuses are extremely strong. For them, to grasp and open a door is trivial, given their dexterity. If we can learn from octopuses, then we can apply that to making an underwater vehicle or robot,” says Wardill. Underwater vehicles inspired by octopuses could play a crucial role in deep ocean exploration. —CLAIRE WILSON