Marine invertebrates, echinoderms are exclusive to marine environments; none live in fresh water. There are many different species in this family, all of which are fascinating. Some of the most remarkable are the feather stars, which are also known as crinoids. Like other starfish, they are characterized by radial symmetry. There are more than 600 documented feather star species living in most of the world’s oceans at depths ranging from just a few feet in intertidal zones, to miles beneath the surface at the bottom of deep, dark trenches. Let’s dive down for a better look at these extremely photogenic animals.
Feather Star Basics
Feather stars have a cup shaped body with feathery looking arms that project outward from it. These arms, which are called pinnules, are covered in a sticky substance that helps them to catch passing food particles, which they then pass down to their mouths, which are situated on their upper sides. Some feather stars have only five arms; others have as many as two hundred.
All echinoderms have tentacle-like structures, or “tube feet” which are hydraulically controlled and which are often equipped with tiny suction pads. They can move from place to place, however movement is usually quite slow. Feather stars are different from their close cousins in that they have no suction pads, and they can roll, walk, crawl, and swim; however, once they find an environment where food is plentiful, usually in areas exposed to currents, they tend to stay within a small area. As passive suspension feeders, they do not generate their own current; they simply wait for zooplankton and other nutrients to pass.
Most feather stars have a tendency toward greater nocturnal activity, preferring to extend to feed once the sun goes down; however, you can see them with their arms rolled up during the daytime, if you know where to look. They tend to hide beneath overhangs, and they love to take shelter in small grottoes and caves. While you might find great masses of feather stars in locations where conditions are ideal, they tend to be fairly solitary, and as simple organisms, are not at all social.
Where you find feather stars, you’re likely to find some other animals living in symbiosis. The crinoid clingfish, a tiny ray finned goby that grows to be no longer than 5 centimeters, can be found inhabiting feather stars around the western Pacific area, in places like Fiji, Taiwan, and the Great Barrier Reef in Australia. Elegant Squat Lobsters, which grow to only 2 centimeters in length, can be found throughout the Indo-West Pacific region, feeding on feather star leftovers.
Feather stars occur in a wide range of colors, from stark whites to simple yellows, to brilliant blues with dark bands, to deep wine hues that contrast beautifully with the blue ocean that surrounds them. They are abundant and face no threats other than those posed by loss of habitat and pollution; when diving in areas where they are found, be sure not to touch or disturb them. A few species can sting, and careless divers can damage or destroy them; with care, we can continue to enjoy their beauty for years to come.