Thresholds of polarization vision in octopuses

Abstract

Polarization vision is widespread in nature, mainly among invertebrates, and is used for a range of tasks including navigation, habitat localisation, and communication. In marine environments, some species such as those from the crustacea and cephalopoda that are principally monochromatic, have evolved to use this adaptation to discriminate objects across the whole visual field, an ability similar to our own use of colour vision. The performance of these polarization vision systems varies, and the few cephalopod species tested so far have notably acute thresholds of discrimination. However, most studies to date have used artificial sources of polarized light that produce levels of polarization much higher than found in nature. In this study, the ability of octopus to detect polarization contrasts varying in angle of polarization (AoP) was investigated over a range of different degrees of linear polarization (DoLP) to better judge their visual ability in more ecologically relevant conditions. The ‘just-noticeable-differences’ (JND) of AoP contrasts varied consistently with DoLP. These JND thresholds could be largely explained by their polarization distance, a neurophysical model that effectively calculates the level of activity in opposing horizontally and vertically oriented polarization channels in the cephalopod visual system. Imaging polarimetry from the animals’ natural environment was then used to illustrate the functional advantage that these polarization thresholds may confer in behaviourally relevant contexts.

Comparative brain structure and visual processing in octopus from different habitats

“…The neuroanatomical features and corresponding habit and habitats were based on the current study (three species) and the published literature (four species). [11][12][13][16][17][18][30][31][32][33][34][35][36][37][38]55,[67][68][69]78,79 See also Ta S2), apparent adaptations that go with complex visual tasks and partially social interaction in a complex, well-lit environment.…”

“…[8][9][10][11][12][13][14][15][16][17][18] Our current knowledge of octopus neuroscience and associated complex behavior is predominantly derived from a large number of studies on a primarily nocturnal species, Octopus vulgaris. 10,11,14,[19][20][21][22][23][24][25][26][27][28][29] While some of what we know around biology, ecology, and physiology has also been obtained from another large species, Octopus cyanea, [30][31][32][33][34][35][36][37][38] knowledge of its neuroanatomy was absent prior to this study. Other species, notably the gloomy octopus (Octopus tetricus) and algae octopus (Abdopus aculeatus), have provided information around cognitive ability based mainly on behavioral observation.…”

Octopus Consciousness: The Role of Perceptual Richness

“…Instead, the rhabdomes that are receptor cells in the retina are arranged geometrically, aligned in two dimension perpendicular to each other (as in insects). Octopuses process polarization plane in two channels, allowing them to discriminate the plane of polarization of light, the two-dimensional vibration of light waves [21]. We can ask how octopuses process this dimension and what perceptual richness it offers.…”

“…Polarization sensitivity is attenuated at distances more than 12 m, so they are relatively short-range cues but this is quite a distance for animals who generally weigh less than 1 kg in weight. According to Temple et al [21], octopus polarization sensitivity is good because it is received in these retinal cells oriented in two dimensions 90 degrees from each other. They tested by projecting a looming stimulus onto a viewing screen and noted that the sensitivity to angular polarization (AoP) depended on a background of linear polarization (DoLP).…”

The wing scales of the mother-of-pearl butterfly, Protogoniomorpha parhassus, are thin film reflectors causing strong iridescence and polarization

“…Moreover, tabanids as well as many beetle species use the polarized light reflections of water surfaces to detect a useful place for positing their eggs ( Schwind, 1991 ; Egri et al, 2012 ). In the marine environment, cephalopods and crustaceans exploit polarization patterns for predation or communication ( Daly et al, 2016 ; Temple et al, 2021 ).…”