The starfish is a marine invertebrate belonging to the class Asteroidea, recognized worldwide for its characteristic radial body plan. This single group of animals exhibits an astonishing range of hues unmatched by many other creatures in the ocean. This visual diversity is not random; it is a direct result of evolutionary pressures, diet, and the specific habitats each species occupies. Exploring this vast palette reveals how color functions for survival, communication, and species identification in these fascinating echinoderms.
The Spectrum of Starfish Colors
Starfish display a remarkable color palette that spans nearly the entire spectrum. Common shades include deep reds, brilliant oranges, and vibrant yellows, alongside more subdued tones of brown, gray, and green. The blue sea star is famous for its vivid coloration, but even that species can exhibit morphs of purple, pink, or light aqua hues.
Coloration is rarely uniform, with many species displaying complex patterns to break up their outline against the seafloor. Some sea stars, like the Bat Star, feature mottled or blotchy patterns, while others, such as the Leather Star, have a base color speckled with tiny dots of red or orange. Other species, including the Rose Star, may exhibit distinct striping. These variations in both hue and pattern are often influenced by local diet and environmental conditions, leading to significant color variation even within a single species population.
The Biological Purpose of Starfish Coloration
The colors displayed by sea stars serve various functional roles that are integral to their survival in diverse marine ecosystems. For many species, the coloration provides camouflage, allowing them to blend into the substrate to avoid detection by predators. Pale or sandy-colored starfish often inhabit open, silty bottoms, while those with muted greens and browns are typically found among algae and rocky reefs.
In contrast, some of the most striking colors function as a form of communication known as aposematism. Bright shades of red, orange, and high-contrast patterns signal to potential predators that the sea star is unpalatable or toxic. For instance, the Crown-of-Thorns starfish displays conspicuous coloration that acts as a deterrent, preventing an attack before it begins.
Color is also theorized to play a role in physiological protection, particularly for species living in shallow, sun-drenched waters. The vivid blue pigment found in the Linckia laevigata sea star, for example, is a carotenoprotein complex that acts as a powerful antioxidant. Scientists propose that this pigment helps the sea star cope with the oxidative damage caused by intense sunlight and ultraviolet (UV) radiation.
Linking Color to Species Identity
The specific combination of color and physical texture is a reliable tool used to distinguish between the thousands of known sea star species. The Blood Star (Henricia sanguinolenta) is recognized by its rough texture and its solid, saturated color, which ranges from bright red to reddish-orange. This uniform pigmentation is a defining trait used for field identification.
Another unmistakable example is the Chocolate Chip Starfish (Protoreaster nodosus), which is named for the dark, conical tubercles that resemble chocolate chips. These prominent, often black or dark brown, nodes stand out against the animal’s lighter body, which can be tan, beige, or reddish-brown, making its identity clear even to the casual observer. Similarly, the brilliant, uniform blue of the Linckia laevigata is so distinct that the animal is commonly known simply as the Blue Star.