Other colors are attainable by using a second layer of structures in the cephalopod skin called iridophores (Cooper & Hanlon, 1986). However, these three colors are particularly useful at the depths wherein many camouflaging cephalopods live (Bush et al., 2009). Yet there are certainly other colors that need to be mimicked but which cannot be made by combining "pixels" of just those three. The chromatophores can be opened quickly because they are controlled neurally: squid, cuttlefish and octopuses can change colors within milliseconds (Hanlon, 2007).Ĭamouflage using chromatophores is particularly impressive because chromatophore pigments are typically only red, yellow, or brown (Hanlon et al., 2011). 2, C), is thought to be responsible for contracting the chromatophore after it has opened (Florey, 1969). ![]() The elastomeric properties of the membrane around the pigment granules -the cytoeslastic sacculus (Fig. The radial muscles are thought to be connected to each other by gap junctions (Florey, 1969) so that they ‘dilate' the chromatophore in a symmetrical fashion. Early morphologic and physiologic work by Florey (1969) showed that the radial muscles widen the pigment sac with increasing frequency of the nerve electrical activity. 2, D) to pull outward toward the perimeter of the chromatophore, expanding the central pigment sack (Fig. 2, G) causes the radial muscle fibers of the chromatophore (Fig. Electrical activity within a chromatophore nerve (Fig. Many coleoids share these tissues and organs, but the common and mimic octopuses ( Octopus vulgaris and Thaumoctopus mimicus, respectively) have received much attention in popular media over the past decade (Figure 1).Ĭhromatophores are organs that are present in the skin of many cephalopods, such as squids, cuttlefish, and octopuses, which contain pigment sacs that become more visible as small radial muscles pull the sac open making the pigment expand under the skin. In addition to hiding in crevices and small holes that these soft-body mollusks easily fit into (Sheel & Bisson, 2012), many cephalopods rely on sophisticated tissues - the chromatophores, iridophores, leucophores and papillae - to blend in with their surroundings and disrupt their body outlines, making them much more difficult to locate by sight. Survival might be hopeless for soft bodied coleoid cephalopods if it were not for camouflage. Yet based on molecular findings, coleoid cephalopods have been present since the early Devonian period, diverging from their ancestor over 400 million years ago (Bergmann et al., 2006). Coleoid cephalopods, a group that includes octopuses, cuttlefish and squid, experience the selective pressure of predation from eels, nurse sharks, and a great many fishes (Aronson, 1991). ![]() The ocean can be a dangerous place, and being a squishy piece of delicious, nutritious muscle is not ideal given that so many capable predators abound.
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