Octopus bimaculoides visually-evoked prey capture

Octopus limb hyper-redundancy complicates traditional motor control system
theory by its extensive sensory inputs, subsequent decision making and arm
coordination. Octopus are thought to reduce flexibility control complexity
by relying on highly stereotypical motor primitives (e.g. reaching and
crawling) and multi-level processes to coordinate movement utilizing
extensive peripheral nervous system (PNS) processing. Division of labor
along the anterior-posterior axis and limb- specialization of the four
anterior arms in T-maze food retrieval further simplify control. Yet,
specific arm recruitment and coordination during visually guided reaching
behavior remains poorly understood. Here, we investigated visually
triggered Octopus bimaculoides hunting capabilities by eliciting and
examining prey-specific arm recruitment. When striking crabs, octopus
preferred synchronous arm recruitment while sequential arm recruitment
with a characteristic swaying movement is employed for shrimp. Such
behavioral selection aligns with specific prey escape strategies and the
octopus' flexible arm biomechanical constraints. Although side bias
existed, we found significant bilateral symmetry, with one side being
functionally a mirror of the other rather than anterior arm use being
functionally equal and differing to posterior arm use. Among arms, the
second limb is unequivocally dominant for goal-directed monocularly driven
prey capture. While the eight arms share gross anatomy and are considered
equipotential, such arm specialization for specific actions could reflect
different degrees of specialization in organismal structures. Finally, we
quantitatively show, corroborating earlier observations, that octopus
employ a dimension reduction strategy by actively deciding to recruit
adjacent arms over other available arms during either sequential or
synchronous visually triggered prey attack.