Platelets Reflect Light

a small sand color marine creature resembling a squid is seen underwater

Biological Strategy

Bobtail squid

AskNature Team

Image: Rickard Zerpe / Wikimedia Commons / CC BY - Creative Commons Attribution alone

Modify Light/Color

Color in living systems comes from pigments and the interaction of light with surfaces. Color serves many purposes for living systems, such as attracting prey or mates, providing warnings, or protecting through camouflage. To create the effects needed for each purpose, living systems must control the expression or visibility of pigments and the interactions (such as reflectance and refraction) of light. To do so, they have strategies that modify color or light to increase or decrease the color’s position, intensity, opacity, and more. Male hummingbirds, for example, have brightly colored feather patches on their throats; the coloring comes from pigments, structures that refract light, or a combination of the two. When a male hummingbird hovers near a potential mate, it modifies the angle of these feathers to create a bright, colorful display. However, when it needs to mute the colors to reduce conspicuousness, such as to avoid a predator, it modifies the angle again.

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Cephalopods

Class Cephalopoda (“head-foot”): Nautilus, squid, octopus, cuttlefish

Cephalopods are unique among mollusks, and even within the animal kingdom. They are lauded for their large brains and complex behaviors and are considered the most intelligent invertebrates. Among 800 species in 45 families, all are carnivorous and live in marine ecosystems. They all have a set of arms or tentacles, but only the nautilus retains an exterior chambered shell. Many species have chromatophores, which allow them to change color for defense, camouflage, or courting. They range from the size of a fingernail to just longer than a city bus (the mysterious giant squid).

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Reflector platelets within squid chromatophores reflect light because they are nanofabricated photonic structures composed of proteins called reflectins.

“The cuttlefish, octopus, and squid are the undisputed champions of camouflage… They can instantly modulate their color, shading, patchiness, mottling or stippling, transparency, heat, and even bioluminescence, light-polarity, or iridescence.”

Read more about the shape-shifting abilities of cephalopods, including the bobtail squid, in Tamsin Woolley-Barker’s “Learning from the Master Shape-Shifter: Cephalopod Technologies” in Zygote Quarterly:

Image: Nick Hobgood / Wikimedia commons /

Bobtail squid from East Timor (Euprymna berryi).

Image: Nick Hobgood / Wikimedia commons /

Bobtail squid (Euprymna scolopes) in two of its color forms, white and orange. These small squid, no more than an inch long can change their color rapidly.

Last Updated November 3, 2020

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