Cephalopod skin displays: from concealment to communication

At first glance, the complex cephalopod skin display system, which Packard (1995) describes as a neuromuscular image generator, looks like the ultimate flexible sender system for visual communication. It is matched by conspecific receivers’ high-acuity-lens eyes (Budelmann, 1994; Muntz, 1999), an excellent example of convergent evolution with the vertebrate eye. But a closer look shows that the sender–receiver match is not so simple. The skin display system apparently evolved as an avoidance communication to potential vertebrate predators (Packard, 1972). Since any sender–receiver system must match the receiver’s sensitivity (Endler, 1992, describes this as sensory drive), the sender system of the cephalopod skin evolved primarily to fit the receiver characteristics of the vertebrate and not the cephalopod visual system. Camouflage patterns are widespread across the group but intraspecies displays are much less so, and even species having them develop them late in ontogeny. Thus cephalopods appear to have adapted the particular characteristics of a system designed for one purpose (Packard, 1995) to another: communication to conspecifics