Feather Star Fish Koh Tao


Learn about the Featherstar Fish on Koh Tao

A Featherstar Fish is a crinoid and a marine animal not a plant and they are one of the oldest form of Echinoderms that belong to the Phylum Echinodermata and the class of Crinoidea.

They are over 200 million years old, which makes them a real-life living fossil and the feathery appearance of their arms gives them their name of Featherstar Fish.

Featherstar Fish are closely related to other marine animals known as Sea Stars, Brittle Stars, Sea Cucumber and Sea Urchins.

Feather Star Fish Marine Life
Feather Star Fish Marine Life

Where to find the Featherstar Fish on Koh Tao

Featherstar Fish are typically found in shallow water and they need a constant flow of ocean current that yields more opportunities to catch food.

They live on or near rocky substrates where they find their food and where they can also attach themselves.

They tend not to live around silt that clogs their feet and if disturbed they will swim through the water column.

Featherstar Fish Koh Tao Dive Sites

You can see them at Koh Tao dive sites such as White Rock or Shark Island, but they often hide during the day.

The best opportunity to see one of these weird and wonderful creatures is at night and White Rock is a great place to see these feathery creatures during a night dive.

Feather Star Fish
Feather Star Fish

How to Identify the Featherstar Fish on Koh Tao

The body of the Featherstar Fish is cup-shaped and they have ten feathery arms that can grow up to 100 mm but average much less and their color varies from rose to deep purple, yellow, orange or mottled and spotted.

Anatomy of a Featherstar Fish

Featherstar Fish have an internal skeleton that comprises calcium carbonate plates covered by a skin and they also have ligaments and muscles that hold the body together.

Like other Echinoderms they have radial symmetry with their mouths located in the centre.

Featherstar Fish have four body parts:

  • Holdfast – which provides an anchor to the substrate
  • Stem – a muscle that raises the Calyx
  • Calyx – is cup shaped and comprises the internal organs
  • Arms – in various numbers

The feathery arms are called pinnules and the pinnules curl in while the Featherstar Fish rests and spreads out when they feed or swim.

Cirri are tiny legs on the end of the pinnules that help to attach them to substrates.

Featherstar Fish rely on camouflage to help them blend into the surrounding Coral and plants and they also exhibit vivid colours especially in shallow water.

Featherstar Fish Characteristics & Behaviour

Featherstar Fish can be both male and female and reproduce by spawning and once the spawning is complete, they wave their arms to disperse the eggs, although some species leave eggs attached onto the pinnules.

About 16 hours after fertilization, larvae hatch from eggs and start swimming in the sea water.

Featherstar Fish swim by moving their arms up and down, although sometimes they parachute off one area and use their cirri to grasp and attach to new substrate and they can move fast with a top speed of 180 metres an hour.

Featherstar Fish are Fast Swimmers

Featherstar Fish eat at night and use their fern-like arms to capture their food, which is plankton and nutrients from the water around them.

After capturing their food, they use their feet to pass the food along from foot to foot until it reaches their mouth and then it enters a U-shaped digestive system with their mouth close to their Anus.

Most Featherstar Fish do not need to hunt for food, instead they wait until they snag food particles on their sticky Velcro like arms and then digest it and then shrimp or snails may consume the resulting feces.

Feather Star Fish Attached to Substrate
Feather Star Fish Attached to Substrate

Interesting Facts about the Featherstar Fish

Featherstar Fish regrow their limbs and as far as we know they can grow infinite numbers of arms, which helps if attacked by predators as they will give up an arm or two to escape, knowing they can grow it back easily.

There are a number of Featherstar Fish species that cannot swim and instead are only able to crawl along the bottom.

Predators of Featherstar Fish

Fish and Sea Urchins will eat Featherstar Fish and other small animals that live on the Featherstar, will also occasionally snack on their hosts.

Featherstar Fish reproduce every 10-16 months and their life cycle depends on a strict timeframe, so if a mating season is disrupted due to a natural event, populations can be at risk.