The animal kingdom presents an astonishing palette of colors, but true purple is a particularly unique and rare hue. While many creatures display vibrant shades, those that possess genuine purple are truly captivating. This article explores how some animals display this striking color and highlights various examples.
The Science of Purple
Animals display purple through two primary mechanisms: pigments and structural coloration. Pigments are colored chemical compounds produced by the animal’s body or acquired through its diet, which absorb certain wavelengths of light and reflect others. True purple pigments are uncommon; purple coloration often results from a combination of red and blue pigments, or from specific compounds like polyketides in sea urchins.
Structural coloration is a more frequent method for animals to appear purple. This phenomenon occurs when microscopic structures on an animal’s surface, such as scales, feathers, or exoskeletons, interfere with light. These structures are precisely arranged to reflect specific wavelengths, like blue and red, which the eye then perceives as purple. The color can appear to shift or shimmer depending on the viewing angle, due to the way light interacts with these intricate arrangements.
A Spectrum of Purple Animals
The animal world showcases a diverse range of creatures that exhibit purple coloration. From marine invertebrates to birds and insects, purple serves various purposes, including camouflage, warning, and mate attraction.
The purple sea urchin (Strongylocentrotus purpuratus) is a notable marine example. Its distinctive dark purple hue comes from pigments, specifically echinochromes and spinochromes, found within its tissues and spines. These pigments are synthesized by the urchin and can change from a lighter green in larvae to the characteristic deep purple in adults.
Purple jellyfish, such as Pelagia noctiluca (Mauve Stinger) or the Purple-Striped Jelly, also display this color. Their purple coloration can be due to specific pigments within their tissues or influenced by their diet, as seen in Moon Jellies that consume pigment-rich prey. Nudibranchs, or sea slugs, also display vivid purples, often acquiring pigments from their diet of sponges or other invertebrates, which they then use for defense or camouflage.
In the avian world, the Violet-backed Starling (Cinnyricinclus leucogaster) exhibits iridescent purple plumage, predominantly in males. This vibrant coloration is a result of structural coloration, where the microscopic structure of their feathers reflects light to create the metallic purple sheen. The males use this display to attract females, who typically have more subdued brown and white feathers, offering better camouflage. The Purple Emperor Butterfly (Apatura iris) displays purple iridescence on the dorsal side of the male’s wings. This effect is achieved through structural coloration, where tightly packed, multilayered ridges on their wing scales interact with light to produce the shimmering blue-purple.
Even amphibians can be purple, though it is rare. The Indian Purple Frog (Nasikabatrachus sahyadrensis) is an unusual species with a bloated, dark purple to grayish body. Its color is inherent to its skin, and it spends most of its life underground, emerging briefly during monsoon season to breed. The color of some frogs, including certain poison dart frogs, is largely structural, produced by nanocrystals in the skin that interact with pigments.