To investigate these unknown octopus features, in this study we examined how and how much octopuses extend their arms to reach an object at the end of a tube, describing a new method for the measurement of octopus arm elongation during reaching movements, and presenting for first preliminary data on sex- and size-related differences.
We designed and developed instruments to be used to directly measure arm elongation in a non-invasive manner in order to compare and determine differential animal performance. The apparatus is a graduated transparent Plexiglas® tube attached to a support plate and is used to measure the performance of individual arms. The animals elongate an arm up the graduated tube to reach a piece of bait used as a reward, which allows the measurement of arm extension. 12 males and 7 females of Octopus vulgaris were exposed to this setup and measured using an experimental protocol that was supported by high-resolution video recordings.