21 February 2012

Australian and UK researchers have made new findings about a form of secret language in the animal kingdom using polarization, a type of light that humans cannot see.

In a new paper published in Current Biology, researchers at The University of Queensland’s (UQ) Queensland Brain Institute and at the University of Bristol in the UK have examined polarization vision and its significance in biological signalling.

They focused on a type of cuttlefish (close relative to octopus and squid) to demonstrate how polarization could be used as an important kind of communication in the animal kingdom.

The paper shows cephalopods such as cuttlefish have the ability to see in many more directions of polarized light than previously thought.

Co-author Professor Justin Marshall, who has published more 20 scientific papers on polarization, said humans had not yet developed the language to describe all the roles of polarization in nature.

Professor Marshall said most people would be familiar with the concept of polarization through the use of polarized sunglasses, but polarization also had an important application in the detection of skin cancer in humans, as a viewing scope containing polarized light was a technology currently used to detect melanomas.

“Our work is borrowing from millions of years of evolution, so perhaps we can learn a lot from nature in terms of better solutions to the problems mankind faces,” he said.

It has been known for years that many animals have better colour vision than humans and also many have polarization vision (P-vision). They literally see things that we can’t.

The polarization of light is a dimension of reality invisible to most people without specialized instruments.

“Mammals and some other groups, don’t appear to have P-vision, although many parts of the animal kingdom do,” he said.

“For example, other studies have found that animals such as ants and bees and even fish may used polarization to navigate.

“Polarization in animals has previously just been categorized as just an unusual and interesting phenomenon but the work we’ve done in the past few years shows that animals use P-vision in the same way we use colour, to communicate with each other.”

Professor Marshall said ironically animals such as cephalopods (cuttlefish, squid and octopi) and many crustaceans were colour blind. Instead they have concentrated on polarisation vision.

“They have evolved perfectly to see light we cannot see and also use polarized skin patterns to camouflage into their backgrounds, giving them an advantage over some predators who did not have P-vision.

“While colour is very useful in terrestrial or shallow-water environments, it is an unreliable cue deeper in water due to the spectral modification of light as it travels through water of various depths or of varying optical quality,” he said.

“Here, polarization vision and communication has special utility and consequently has evolved in numerous marine species, as well as at least one terrestrial animal.”

Professor Marshall, of UQ's Queensland Brain Institute, last year received $962,000, including a Discovery Outstanding Researcher Award (DORA), for a three-year study of colour and polarization vision on the Great Barrier Reef.

As the tightest-packed ecosystem on the planet, coral reefs make for a competitive environment, from which has evolved unique sensory adaptations that Professor Marshall's research will investigate.

His laboratory has developed a range of techniques and methods, such as underwater spectrophotometry, photography, unique behavioural tests and mathematical modeling of animal vision to understand the design of visual signals and systems in the light of ecology, behaviour and evolution.”

Media: Professor Justin Marshall (07 3365 1397, 0423 024 162) or Jan King (0413 601 248).