Self-Recognition Mechanism between Skin and Suckers Prevents Octopus Arms from Interfering with Each Other

Abstract

Controlling movements of flexible arms is a challenging task for the octopus because of the virtually infinite number of degrees of freedom (DOFs) [1, 2]. Octopuses simplify this control by using stereotypical motion patterns that reduce the DOFs, in the control space, to a workable few [2]. These movements are triggered by the brain and are generated by motor programs embedded in the peripheral neuromuscular system of the arm [3-5]. The hundreds of suckers along each arm have a tendency to stick to almost any object they contact [6-9]. The existence of this reflex could pose significant problems with unplanned interactions between the arms if not appropriately managed. This problem is likely to be accentuated because it is accepted that octopuses are "not aware of their arms" [10-14]. Here we report of a self-recognition mechanism that has a novel role in motor control, restraining the arms from interfering with each other. We show that the suckers of amputated arms never attach to octopus skin because a chemical in the skin inhibits the attachment reflex of the suckers. The peripheral mechanism appears to be overridden by central control because, in contrast to amputated arms, behaving octopuses sometime grab amputated arms. Surprisingly, octopuses seem to identify their own amputated arms, as they treat arms of other octopuses like food more often than their own. This self-recognition mechanism is a novel peripheral component in the embodied organization of the adaptive interactions between the octopus's brain, body, and environment [15, 16].

Bodily Processing: The Role of Morphological Computation

“…We can say that, in any case, organisms phyloand ontogenetically learn their own morphology, their possibilities, and constraints and then exploit them in their actions and perceptions. We can observe this in octopuses [36] to the same degree as in human infants [37]. I believe that this research can be the first step to solving the body-role problem.…”

Information processing in the CNS: a supramolecular chemistry?

“…• A self-recognition peripheral mechanism between skin and suckers in octopus prevents their arms from interfering with each other, via chemical signals that inhibit the attachment reflex (Nesher et al 2014). • Bumblebees can detect and discriminate the variations in pattern and structure exhibited by floral electric fields (Clarke et al 2013).…”

Sensorial Hierarchy in Octopus vulgaris’s Food Choice: Chemical vs. Visual

“…Furthermore, it has been highlighted that the octopus's olfactory organ is able to change shape, from relaxed to erect to perceive water-soluble compounds such as salts, sugars, amino acids, amines, peptides, proteins, and functionalised hydrocarbons, which allows the animal to orient itself to detect the spatial gradient of these chemical cues, helping in navigation and triggering spatial memories [23,57,74,75]. Octopuses also possess a self-recognition mechanism, which consists of the attachment reflex inhibition of their own suckers, due to chemical signals in the skin [76]. Recently, it has been hypothesised that olfaction in octopus is not restricted to the olfactory organ, but it is also extended to other structures such as the suckers, that were traditionally not considered olfactive.…”