Mechanisms and behavioural functions of structural coloration in cephalopods

Abstract

Octopus, squid and cuttlefish are renowned for rapid adaptive coloration that is used for a wide range of communication and camouflage. Structural coloration plays a key role in augmenting the skin patterning that is produced largely by neurally controlled pigmented chromatophore organs. While most iridescence and white scattering is produced by passive reflectance or diffusion, some iridophores in squid are actively controlled via a unique cholinergic, non-synaptic neural system. We review the recent anatomical and experimental evidence regarding the mechanisms of reflection and diffusion of light by the different cell types (iridophores and leucophores) of various cephalopod species. The structures that are responsible for the optical effects of some iridophores and leucophores have recently been shown to be proteins. Optical interactions with the overlying pigmented chromatophores are complex, and the recent measurements are presented and synthesized. Polarized light reflected from iridophores can be passed through the chromatophores, thus enabling the use of a discrete communication channel, because cephalopods are especially sensitive to polarized light. We illustrate how structural coloration contributes to the overall appearance of the cephalopods during intra-and interspecific behavioural interactions including camouflage.

Mechanism of variable structural colour in the neon tetra: quantitative evaluation of the Venetian blind model

“…Some cephalopod species (squid, cuttlefish and octopus) exhibit a remarkable colour change: the body pattern can be almost instantaneously changed for camouflage and signalling [31,32]. In particular, a unique structural variation has been observed inside a dermal iridophore of a squid, Lolliguncula brevis: a multilayer reflector is gradually formed using proteinaceous material during the appearance of iridescence [33,34].…”

Cephalopod-inspired design of electro-mechano-chemically responsive elastomers for on-demand fluorescent patterning

“…To design these responsive soft material systems, various strategies have been exploited, such as embedding rigid light-emitting diodes into elastomeric substrates [3][4][5][6][7] , employing stretchable electro-luminescent polymers 1,8,9,11 and designing microfluidic networks filled with controlled pigment fluids 10,[12][13][14][15] . On the other hand, nature offers a drastically different strategy that enables soft skins of animals to spontaneously display versatile colours and fluorescence 10,16,17 . For example, cephalopods (including cuttlefish, octopuses and squids) [16][17][18][19] can display dazzling patterns of colours for signalling or active camouflage in response to environmental stimuli.…”

“…On the other hand, nature offers a drastically different strategy that enables soft skins of animals to spontaneously display versatile colours and fluorescence 10,16,17 . For example, cephalopods (including cuttlefish, octopuses and squids) [16][17][18][19] can display dazzling patterns of colours for signalling or active camouflage in response to environmental stimuli. The colouration generally relies on skin chromatophores composed of pigment-containing sacs that are attached to multiple radial muscles 16,20 (Fig.…”

“…For example, cephalopods (including cuttlefish, octopuses and squids) [16][17][18][19] can display dazzling patterns of colours for signalling or active camouflage in response to environmental stimuli. The colouration generally relies on skin chromatophores composed of pigment-containing sacs that are attached to multiple radial muscles 16,20 (Fig. 1a,b).…”

Tunable structural color in organisms and photonic materials for design of bioinspired materials

“…This mechanism is slightly different from that of the cobalt blue shown in figure 1(B). According to a recent review [26], squid, octopus and cuttlefish use this mechanism for camouflage and communication.…”