Meeting Abstract
The goal of this study is to determine the time of onset, duration, and range of movements that occur when different regions of an amputated octopus arm are exposed to a noxious chemical stimulus. Randomized trials were conducted to assess the relative sensitivities of and movements elicited in the proximal oral, proximal aboral, distal oral, and distal aboral regions. It was hypothesized that the oral regions would be most sensitive due to the purported higher density of chemoreceptors on the suckers compared to the rest of the skin. Experiments were carried out on arms from 12 specimens of wild-caught Octopus bimaculoides, with five to six arms utilized per specimen. Animal husbandry and experimental protocols were based on guidelines developed by the international cephalopod research community, with ethanol utilized as an analgesic and anesthetic. Fifty percent acetic acid vapor was introduced through diffusion, at a distance of 5-10 mm, to a vertically suspended amputated arm. The movements elicited were video recorded at 30 frames per second and later coded qualitatively and quantitatively. A diverse array of arm movements were elicited, such as bends, helical twists, and shortening. Data were analyzed according to the four regions of stimulus, distal versus proximal regions, and oral versus aboral regions. The effect of arm identity was also examined. These data may provide insights into the degree to which arm movements are controlled by the nerves within the arm versus more centralized control centers, such as the brain or the interbrachial commissure, which connects the axial nerve cords of adjacent arms.
