Biology subjects

Sivitilli, D. M.

Publications and source records attributed to Sivitilli, D. M..

3 recordsLinked to original sources

bioRxiv2023

Octopus arm search strategies over complex surfaces

Despite the extreme flexibility of the octopuss arms and their resulting near infinite possible configurations, the octopus effectively controls its arms during a wide variety of behaviors, including locomotion, foraging, excavation, exploration, and manipulation. If appropriately characterized, the octopuss biomechanical properties and control strategies could be implemented in the development of a soft robotic limb with the same range of capabilities. When operating without visual feedback, the octopus must rely on the complex chemotactile sensory system within its suckers, and in these conditions sucker recruitment plays a prominent role in search behavior, causing the arm to conform to surface features in the environment. However, how this mechanism is used to search over the complex and convoluted surfaces in the octopuss natural habitat is unknown. Here, we investigate the strategies the octopus uses to search for a reward hidden among a row of multiple small openings of a task space, and how it uses multiple arms to search three parallel versions of this task space. We found that when the arm encounters multiple openings in a surface, it performs a distal to proximal search pattern, starting with the farthest openings within reach then working its way proximally with a preference for searching each opening in succession. This strategy would allow the octopus to use its highly flexible limbs to perform an exhaustive search pattern over complex surfaces.

animal behavior and cognition↗

bioRxiv2023

Mechanisms of octopus arm search behavior without visual feedback

The octopus coordinates multiple, highly flexible arms with the support of a complex distributed nervous system. The octopuss suckers, staggered along each arm, are employed in a wide range of behaviors. Many of these behaviors, such as foraging in visually occluded spaces, are executed under conditions of limited or absent visual feedback. In coordinating unseen limbs with seemingly infinite degrees of freedom across a variety of adaptive behaviors, the octopus appears to have solved a significant control problem facing the field of soft-bodied robotics. To study the strategies that the octopus uses to find and capture prey within unseen spaces, we designed and 3D printed visually occluded foraging tasks and tracked arm motion as the octopus attempted to find and retrieve a food reward. By varying the location of the food reward within these tasks, we can characterize how the arms and suckers adapt to their environment to find and capture prey. We compared these results to simulated experimental conditions performed by a model octopus arm to isolate the primary mechanisms driving our experimental observations. We found that the octopus relies on a contact-based search strategy that emerges from local sucker coordination to simplify the control of its soft, highly flexible limbs.

animal behavior and cognition↗

bioRxiv2021

The lesser Pacific striped octopus, Octopus chierchiae: an emerging laboratory model for the study of octopuses

Cephalopods have the potential to become useful experimental models in various fields of science, particularly in neuroscience, physiology, and behavior. Their complex nervous systems, intricate color- and texture-changing body patterns, and problem-solving abilities have attracted the attention of the biological research community, while the high growth rates and short life cycles of some species render them suitable for laboratory culture. Octopus chierchiae is a small octopus native to the central Pacific coast of North America whose predictable reproduction, short time to maturity, small adult size, and ability to lay multiple egg clutches (iteroparity) make this species ideally suited to laboratory culture. Here we describe novel methods for culture of O. chierchiae, with emphasis on enclosure designs, feeding regimes, and breeding management. Our results demonstrate the feasibility of multigenerational culture of O. chierchiae. Specifically, O. chierchiae bred in the laboratory grows from a 3.5-millimeter mantle length at hatching to an adult mantle length of approximately 20-30 millimeters in 250-300 days, with 14-15% survivorship to over 400 days of age in first and second generations. O. chierchiae sexually matures at around an estimated six months of age and, unlike most octopus species, can lay multiple clutches of eggs, approximately every 30-90 days. Eggs are large and hatchlings emerge as direct developing octopuses. Based on these results, we propose that O. chierchiae possesses both the practical and biological features needed for a model octopus that can be cultured repeatedly to address a wide range of fundamental biological questions.

animal behavior and cognition↗