Cuttlefish colour vision theory described in Science (AAAS) News 6 July 2016 and PNAS doi: 10.1073/pnas.1524578113, published online 5 July 2016. Cuttlefish, octopuses and squid, collectively called cephalopods, can rapidly change colour to match different surroundings, and they also signal to one another using colour changes. This has intrigued scientists because their eyes only have one kind of light sensitive protein, which means they should not be able to see colour. So how do they know the colour of their surroundings, or communicate using colour?
A biologist from University of California, Berkeley, and a physicist from Harvard University have come up with an intriguing theory. Each colour in the visible spectrum is a different wavelength of light, and when light passes through a lens the different wavelengths are bent at slightly different angles, which means they do not focus on exactly the same plane. This effect is called chromatic aberration, and the researchers suggest cephalopods can determine colours by rapidly changing focus and sensing the different wavelengths as they went in and out of focus. The chromatic aberration effect would be enhanced by the oddly shaped off-centre pupils that cephalopods have.
To test their theory the scientist designed a computer model which showed “how chromatic aberration can be exploited to obtain spectral (colour) information, especially through non-axial pupils that are characteristic of coleoid cephalopods”. They claim their model offers “a possible solution to the apparent paradox of vivid chromatic behaviours in colour blind animals”.
Editorial Comment: Don’t miss it! Such a dynamic method of seeing colour would only work if the animal’s brain was set up to interpret the changing focus, which is why the scientists had to use a well-designed pre-programmed computer model to see if it could work. Computer models only work because a creative software designer ‘made’ a program to interpret the information collected by the eye.
If this is how cephalopods see colour it would explain another characteristic of the cephalopod eye – the arrangement of cells in its retina. In the invertebrate cephalopod eye the photoreceptors are in the front layer of the retina, which is the opposite of a vertebrate eye, which has its photoreceptors at the back. For many years sceptics, such as Richard Dawkins have held up the vertebrate eye as an example of something that had to be an accident of evolution because an intelligent designer would never put the photoreceptors behind other layers of cells. To reinforce their point the sceptics held up the cephalopod eye as an example of evolution getting it right (e.g. “Denton vs squid; the eye as suboptimal design”, Panda’s Thumb website). However, recent research on the vertebrate retina has revealed there are specialised cells in their retina that function like fibre-optic cables and convey light through the layers of the retina, without loss, and these cells also correct chromatic aberration before the light gets to their photoreceptors.
If invertebrate cephalopods use chromatic aberration to see colour then they don’t want to have it corrected before the light gets to their photo receptors, as they need to see light after it has been bent, but before it passes through any other cells. Therefore, cephalopod photoreceptors need to be at the front, i.e. the opposite of vertebrates.
The researchers admitted there needs to be more research on cephalopod vision, and we await the results with interest. Whatever they find, we predict it will confirm all previous research: that eyes and brains are the brilliant creations of the ultimate optical engineer and software designer – Jesus Christ the Creator. (Ref. optics, molluscs, vision)
Evidence News vol. 16 No. 15
17 August 2016
Creation Research Australia