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Ever wondered why octopuses don’t tie themselves in knots? A team from the Hebrew University of Jerusalem believes they have discovered how they achieve it: a chemical produced by octopus skin temporarily stops the suckers from doing their job.

Experiments have previously demonstrated that octopuses cannot keep track of the precise location of their arms—as the number of limbs and their degrees of freedom would require immense processing power from the octopus brain—so the newly discovered chemical mechanism turns out to be an ingenious solution to a challenging problem.

To show how the octopus manages the feat, the scientists covered Petri dishes with octopus skin and observed how amputated octopus arms (which remain alive for an hour after separation) never grabbed onto the dishes. In other experiments, an extract of the skin was applied to dishes, and it was found that the force with which the amputated arms attached themselves was much less than normal. It was concluded, therefore, that living octopuses are able to control that behavior by making use of this chemical signal in the skin.

The researchers are working to identify the active agent involved, with a possible view to making use of the idea in biologically inspired robot design.

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