Arm Autotomy

The first squid reported to autotomize its arms, O. deletron is the only known cephalopod to break an arm at the point of interaction. It is also one of a very few species to use attack autotomy. In 2012, Stephanie Bush studied this phenomenon by collecting footage from three previous remote operated vehicle dives performed by the Monterey Bay Aquarium Research Institute and by collecting individual members of O. deletron in order to perform experiments. From these observations, it was discovered that the octopus squid can autotomize and regenerate each of its eight arms.

They proposed two mechanisms by which this can occur: (1) the arm is grabbed by a predator which provides the resistance for autotomy, or (2) the arm hooks grasp a potential predator and the attachment provides the resistance for autotomy. Furthermore, O. deletron can severe their arm(s) at numerous places.

Once the arm has been severed, usually at the photophore tip, it thrashes around and emits a bio-luminescent glow. This can deter the predator's attention away from the squid, providing ample time for O. deletron to escape.

It was further discovered that multiple arms can be autotomized at once, and if one arm has already been autotomized, the other arms can still be autotomized during other defensive attacks. This may be because arm regeneration is rapid in O. deletron. They can regenerate up to 2mm of tissue in nine days.

Monterey Bay Research Institute, from video of Octopoteuthis deletron squid encountering a lighted bottle brush (left) and leaving detached bio-luminescent tentacle tip behind (right).