Do cephalopods communicate using polarized light reflections from their skin?

Abstract

SummaryCephalopods (squid, cuttlefish and octopus) are probably best known for their ability to change color and pattern for camouflage and communication. This is made possible by their complex skin, which contains pigmented chromatophore organs and structural light reflectors (iridophores and leucophores). Iridophores create colorful and linearly polarized reflective patterns. Equally interesting, the photoreceptors of cephalopod eyes are arranged in a way to give these animals the ability to detect the linear polarization of incoming light. The capacity to detect polarized light may have a variety of functions, such as prey detection, navigation, orientation and contrast enhancement. Because the skin of cephalopods can produce polarized reflective patterns, it has been postulated that cephalopods could communicate intraspecifically through this visual system. The term 'hidden' or 'private' communication channel has been given to this concept because many cephalopod predators may not be able to see their polarized reflective patterns. We review the evidence for polarization vision as well as polarization signaling in some cephalopod species and provide examples that tend to support the notion -currently unproven -that some cephalopods communicate using polarized light signals.

How does the blue-ringed octopus (Hapalochlaena lunulata) flash its blue rings?

“…Brief iridescence flashes were sometimes observed immediately before male-male and male-female mating attempts (Cheng and Caldwell, 2000). Furthermore, cephalopods have the visual hardware to be able to detect polarized light, and the polarized reflectance at oblique angles may function in communication (Mäthger et al, 2009a) but more work is needed to confirm such a role. It would also be interesting to know whether the blue-ringed octopus can show a partial display (e.g.…”

Giant Australian cuttlefish use mutual assessment to resolve male-male contests

“…We therefore measured the intensity using 158 contrast differences between light and dark bands. Contrast differences are likely to be 159 visually conspicuous because the visual systems of cuttlefish are sensitive to polarized light 160 (Mäthger, Shashar, & Hanlon, 2009; Shashar, Rutledge, & Cronin, 1996). We calculated the 161 brightness of the bands on the mantle of each male displaying passing cloud.…”

Out of the blue: the evolution of horizontally polarized signals inHaptosquilla(Crustacea, Stomatopoda, Protosquillidae)

“…On land, many insects use the celestial polarization pattern for navigation (Wehner, 1976;Rossel and Wehner, 1986;Labhart and Meyer, 1999;Dacke et al, 2003), while in the ocean, some crustaceans and cephalopod molluscs use polarization information to detect prey and possibly as a means of conspecific communication (Shashar et al, 1996;Cronin et al, 2003a;Chiou et al, 2007;Mäthger et al, 2009;Cronin et al, 2009;Chiou et al, 2011). In the context of communication, polarization often forms composite signals with other visual dimensions, such as hue and brightness (Cronin et al, 2003a;Cronin et al, 2009).…”

“…In such changing conditions, the polarization of light remains more constant than other visual dimensions over short ranges (Waterman, 1954;Cronin, 2001), which renders it a reliable provider of information (Shashar et al, 2011;Johnsen et al, 2011). Previous research in this field has focused on either the underlying retinal mechanisms of polarization sensitivity (for reviews, see Horváth and Varjú, 2004;Roberts et al, 2011) or the optical mechanisms by which polarization and multi-component polarization and/or colour signals are produced (Chiou et al, 2005;Mäthger and Hanlon, 2006;Chiou et al, 2007;Mäthger et al, 2009;Cronin et al, 2009). In contrast, the evolutionary context of polarization signal content relative to the visual system of receivers is still very much unknown.…”