AsianScientist (May 17, 2011) – How does a colorblind animal know how to change its skin color to blend into its background? And what does the animal’s predator ‘see’ when looking at its prey before and after it hides?
These questions are addressed in an article published in the journal Proceedings of the National Academy of Sciences (PNAS), by a collaborative team from the Marine Biological Laboratory (MBL) and West Point Academy in the U.S., and National Tsing Hua University in Taiwan.
The team studied marine animals known as coleoid cephalopods (octopus, squid, and cuttlefish). Camouflage is the primary defense in these animals, whose rapidly adaptable body patterning system is among the most sophisticated in the animal kingdom.
The expression of camouflage body patterns in cuttlefish is a visually driven behavior. Previous studies have shown that certain background variables – such as brightness, contrast, edge and size of objects – are essential for eliciting camouflaged body patterns.
However, cephalopod eyes lack color perception, thus the vexing question of how they achieve effective camouflage while being colorblind still remains. Moreover, it is difficult to determine whether a predator actually visually picks out the prey from the background environment. Thus, how does a colorblind animal change its color to blend into its surroundings, and how do predators actually ‘see’ their prey?
Using a new imaging technology called HyperSpectral Imaging (HSI), the team more accurately measured color matches between the animal and its background, and modeled camouflage in the eyes of predators. Unlike human eyes or typical digital cameras, which only capture three narrow windows (Red, Green, Blue – RGB), this technique captures the entire spectrum using 540 windows.
The researchers learned that much of the contrast information which allows a predator to “pick out” a cuttlefish from the background environment resides in the brightness (luminance) rather than in the color (chromatic) aspect of the reflected light.
This means that cuttlefish camouflage strategies leave their predators with only brightness as a method for prey identification.
The team’s findings strongly support that cuttlefish can produce color-coordinated camouflage on natural substrates despite lacking color vision. Understanding the principles of camouflage is not only important in biology, but also provides insights into architecture, advertisement, and defense applications.
The article can be found at: Chiao CC et al. (2011) Hyperspectral imaging of cuttlefish camouflage indicates good color match in the eyes of fish predators.
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Source: Marine Biological Laboratory.
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