Feather stars are animals, not plants. They belong to the echinoderm family, which includes sea stars, brittle stars, sea urchins, and sea cucumbers. They have been around for about 200 million years and are part of the crinoid class. Crinoids are marine invertebrates, and while some, known as sea lilies, stay attached to the sea floor by a stalk, feather stars are unstalked. They crawl and swim in a unique and fascinating way that you’ll find amazing to watch!
Feather starfish start life with a stalk or stem, which they shed as they grow into adults. As adults, they usually have between 5 and 20 arms, depending on the species. They can regenerate lost or damaged arms, similar to starfish; with just one arm and an intact nerve center, they can regrow all their limbs! Their cup-shaped body supports arms that can grow up to about 20 cm long, though they are often shorter. Feather stars come in a range of colors, including black and white, pink, purple, yellow, white and orange, and may have mottled or spotted patterns.
Their internal skeleton consists of calcium carbonate plates covered by skin, with ligaments and muscles helping to maintain stability. Like other echinoderms, feather stars exhibit radial symmetry with their mouth located at the center. Feather stars feed on tiny organisms like plankton and ocean detritus. They use their arms, coated in sticky mucus, to capture food from the water. By spreading their arms in a fan shape, they catch food with their tube feet. The food is then moved to their mouth through a groove lined with tiny hair-like structures called cilia, which help push the food along. They don’t have a stomach; their mouth leads directly to a short esophagus, which connects to their intestine.
Feather stars swim by moving their arms up and down. They also use their cirri; tiny, leg-like structures, to grasp and attach to surfaces like rocks or coral while feeding or moving. They are not fast swimmers; their movement is generally slow and deliberate.
Reproduction
- Feather stars reproduce sexually, with distinct male and female individuals. Most species have their reproductive organs located in the pinnules near the crown, while some have them in the arms.
- During reproduction, the pinnules release eggs and sperm into the water. In some species, the fertilized eggs stick to the arms or are kept in sacs on the pinnules.
- The eggs hatch into free-swimming larvae that don’t eat. After a few days, they settle on the sea floor and transform into stalked juveniles. As they mature into adults, they lose their stalks and become free-swimming.
- Feather stars reach sexual maturity at 12 to 18 months and live for about 15 years.
Predators
Feather stars have several predators, including fish, sea urchins, and crabs. They also form symbiotic relationships with sea snails, lobsters, shrimp, and fish. These small creatures live on the feather stars, offering shelter and safety in return for cleaning off debris and detritus, though they might occasionally feed on the feather stars themselves.
Where to Find Feather stars on Koh Tao
Feather stars can be found at the following dive sites around Koh Tao:
Laem Thian,
Shark island.
They can also be spotted during night dives at White Rock.
