Somewhere in the long human habit of learning from living things, a small study of young common octopuses has added a quiet lesson: a body without bones can still move with method. Researchers in Singapore, Naples and Vienna watched these animals press toward openings narrower than their own soft frames, and found that what looks like pouring is in fact a sequence of probing, shifting and bracing. The finding, reported in the Journal of Experimental Biology, offers engineers a way of thinking about flexible machines, though the animals observed are few and the path from octopus to robot remain
How Octopuses Squeeze Through Gaps Smaller Than Their Bodies, and What Robots Can Learn
An octopus does more than fit through a gap: it finds leverage
Mark
What's the main finding here? Octopuses squeeze through holes, which we already knew.
Mimi
What's new is the order. Probe with one arm, thread several more through, then anchor two arms' suckers on the far side and pull. It's a sequence, not just softness.
Mark
And tighter holes changed it?
Mimi
Yes. The animals facing relatively smaller openings split the last move: all arms first, then the head and mantle.
Luke
Careful, though. Only three common octopuses, each tested at one hole size. The link between tightness and the four-step pattern could be individual differences.
Mark
Why measure eye spacing instead of body width?
Mimi
Eye spacing stands in for the cartilage capsule around the nervous system, the part that doesn't squash much. It gives a fairer comparison with the hole.
Mark
What about the Mayan octopuses?
Luke
Four juveniles didn't try the small hole, so nothing comparable. That doesn't mean the species lacks the strategy. It's simply unknown.
Mark
And the robot angle?
Mimi
Staging a passage could simplify control of a soft body. The mantle is still unmeasured, though.
Luke
And no robot was built or tested here. Rescue uses are a possibility, not a result.
Il Polso
- Three young octopuses face a hole narrower than their own soft bodies, and the question of how they fit through becomes a test of coordinated movement.
- Arms feel their way across the opening first, then more arms follow while the head and mantle wait behind the partition.
- Under tighter conditions, the animals rotate, twist and reposition their whole bodies before dragging the head and mantle across.
- Mayan octopuses did not reproduce the tight-hole maneuver, leaving the strategy's reach across species unresolved.
- The findings are drawing interest toward soft robotics, yet the sample remains small and the mantle's role still needs measuring.
Somewhere in the long human habit of learning from living things, a small study of young common octopuses has added a quiet lesson: a body without bones can still move with method. Researchers in Singapore, Naples and Vienna watched these animals press toward openings narrower than their own soft frames, and found that what looks like pouring is in fact a sequence of probing, shifting and bracing. The finding, reported in the Journal of Experimental Biology, offers engineers a way of thinking about flexible machines, though the animals observed are few and the path from octopus to robot remains long.
Three subadult common octopuses were placed in tanks divided by clear acrylic walls, each with a single central opening. Cameras from several angles recorded how they chose to cross. What appears to the eye as a smooth pour through a gap turns out, on closer viewing, to be orderly work: probing, repositioning and bracing.
The study, from researchers at the National University of Singapore, the University of Naples Federico II and Vienna's Haus des Meeres, measured hole size against the distance between the eyes, a proxy for the cartilage that guards the central nervous system. Of 33 trials, 30 were analyzed. The simpler route used three steps: one arm pushed through and reached beyond, several more followed, and two arms already across anchored their suckers and pulled the body along. Smaller openings called for a fourth step, in which all remaining arms passed first, the body rotated and twisted, and only then the head and mantle were drawn through.
The Mayan octopuses tested in exploratory runs did not show the tight-hole maneuver, though the researchers caution that this does not prove the strategy is absent in their species. The limits are plain: three animals, one hole size each, and mantle movement recorded too loosely to analyze. For robotics, the lesson lies in organization rather than softness alone, since a machine might break a continuous deformation into staged simple actions. The study tested animals, not machines, and the next work will need more individuals and more careful measurement.
Three subadult common octopuses were placed in aquaria divided by clear acrylic partitions, each with a single opening in the middle. Cameras filming from at least two angles recorded what happened when the animals decided to go through. To the eye, an octopus in that situation seems to pour itself through the hole. The footage shows something more orderly: probing, repositioning and bracing.
The work comes from researchers at the National University of Singapore, the University of Naples Federico II and Vienna's Haus des Meeres–Aqua Terra Zoo, and it appears in the Journal of Experimental Biology. The team included Wenci Xin, Michael J. Kuba, Tamar Gutnick, Daniel Abed-Navandi and Cecilia Laschi. They worked mainly with Octopus vulgaris, and ran additional exploratory tests with Mayan octopuses, Octopus maya. Xin said octopuses can change shape to get through tiny holes, almost like water flowing through a gap, so size does not always limit where they can go.
The researchers did not measure hole size against the animal's soft outline. They used the distance between the eyes, a stand-in for the cartilage capsule around the central nervous system, which deforms less than the rest of the body. One octopus with an eye spacing of 15 to 20 millimeters faced a 20-millimeter opening. The other two, with eye spacing of 30 to 35 millimeters, faced 30-millimeter holes. Of 33 recorded trials, three failed because the animal tried to escape elsewhere and damaged the apparatus, leaving 30 for analysis.
The simpler sequence had three steps. First, the octopus pushed one arm through, bending it near the hole and extending it beyond, to make contact with the space on the other side. Second, more arms followed, three to five of them, with four the most common, filling much of the opening while the head, mantle and remaining arms stayed behind. Third, two arms already across twisted back and attached their suckers to the far side of the partition. Stiffening and extending against it, they pulled the rest of the body through.
The octopuses facing relatively smaller openings added a fourth step. After probing and shifting, they first moved all remaining arms through, rotating their bodies upward and twisting and extending to bring the arms past the partition. Only then did they restore their orientation and, with arms braced against the barrier, pull the head and mantle across. Side views showed the mantle actively changing shape and narrowing before passage, but the recordings concentrated on arms and head, so the team could not analyze mantle movement systematically.
The Mayan octopuses did not reproduce the tight-hole maneuver. Four juveniles showed no attempt to squeeze through the smaller opening, so no comparable analysis was possible. They did pass through larger openings using the three-step sequence. One Mayan octopus offered several openings explored a smaller one and shifted two arms in, but did not continue; it later used the larger central opening. The researchers say this does not establish that Mayan octopuses generally lack the four-step strategy.
The common-octopus sample carries its own limits. Each of the three animals was tested at only one relative hole size, so the link between strategy and opening size could partly reflect individual differences. Front-left arms often started the probing, but the setup gave clearer visibility on one side, which may explain that apparent bias. Repeated trials strengthen the behavioral record without replacing more animals.
For robotics, the lesson is organization as much as softness. A robot could combine simple actions such as probing, anchoring and pulling into a staged sequence, easing the burden of controlling a continuously deforming body all at once. Search-and-rescue and underwater exploration are named as possible uses, but the study tested animals, not machines, and showed no robot working through rubble. The next experiments need more individuals, several hole sizes per animal and better measurement of mantle deformation.
Citazioni salienti
Octopuses can change their body shape to squeeze through tiny holes, almost like water flowing through a gap, so their size doesn't always limit where they can go.— Wenci Xin, study researcher
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