Meeting Abstract
Cephalopods have remarkable camouflage abilities that rely on the expansion and contraction of tiny pigment organs in the skin called chromatophores. These organs are composed of a central pigment sac attached to a ring of spoke-like chromatophore muscles. The muscles are innervated by motoneurons originating in the brain which project their axons via the pallial nerve. When activated, chromatophore muscles contract, expanding the pigment sac to several times its original size, making it more visible to the eye. Previous work on chromatophore muscles identified neural inputs and revealed electrical coupling between adjacent muscles of the same chromatophore. Here we used the hatching squid (Sepioteuthis lessoniana) to further investigate the response of chromatophore muscles to neural inputs and determine the characteristics of electrical coupling between muscles. We conducted dual whole cell patch clamp recordings from muscle pairs of the same chromatophore positioned at varying locations around the pigment sac. We found a high degree of electrical coupling between all muscle pairs in square wave current injection experiments, even when they were positioned opposite one another around the chromatophore. We also recorded spontaneous activity and responses to stimulation of the pallial nerve in muscle pairs. We found that spontaneous and evoked activity in all muscles of the same chromatophore were highly correlated in timing and amplitude, regardless the location of the muscles around the chromatophore. Our results suggest that extensive electrical coupling functions in causing the chromatophore muscles to activate together and expand evenly, producing a circular expansion of the pigment sac that may be more efficient in generating color change.
