Octopuses adjust their sequence of movements to squeeze through
· BehindLines newsroom
An octopus can push its arms through a small opening without the rest of its body immediately following. A study published on November 5 in the Journal of Experimental Biology describes how the animals organise this crossing. The observations, also reported by Science News, reveal different sequences in the situations examined.
Researchers followed 3 subadult common octopuses and 4 juvenile Maya octopuses. A transparent partition divided the experimental spaces. Videos recorded from several angles allowed movements to be analysed frame by frame, rather than simply checking whether an animal reached the other side.
Arms also provide support
In a sequence of 3 stages, one arm first explores the opening, more arms enter, and the rest of the body then passes through. Arms already across do more than pull without support: some turn back towards the partition and anchor themselves with their suckers.
When an opening was narrower than the distance between their eyes, the common octopuses observed separated their movements further. The remaining arms went through before the head and mantle moved in a separate stage, bringing the described sequence to 4 stages. Hole size was compared with eye spacing, used as an indicator of the width of the nervous system’s cartilaginous covering.
Observations on a small scale
The findings do not establish a rule for every octopus. Each common octopus was tested in only one condition, so the effect of the opening and individual preferences cannot be confidently separated.
The Maya octopus experiments remain exploratory. The animals did not attempt the initial narrow passages; when offered several openings, partial attempts preceded a crossing through a large hole. Saying they never try would therefore go too far.
The team suggests possible inspiration for soft robotics. The study chiefly supplies a detailed description of animal movements; it does not present a robot already able to reproduce these crossings.