Crinoids or Feather Stars

Witness The Beautiful Crinoids Or Feather Stars On The Reefs Off Port Douglas

On every trip with ABC Snorkel Charters Port Douglas, we see beautiful and highly ornate Feather Stars sitting at the edge of coral walls waving in the current. They can be found at depths up to 200 metres, but we frequently find them in much shallower water, starting at just 5 metres, which is common in the tropical waters of The Great Barrier Reef. Although plant like in appearance, they are in fact animals from a group called Crinoids and fossil records have established they evolved at least 450 million years ago.

The Feather Stars we see on a daily basis are particularly beautiful and come in a range of vibrant colours, from black to orange, to green and yellow. To look at them, they appear to have multiple stubby legs (called cirri) that anchor onto the coral substrate, locking them into place even in strong currents. These legs also give them mobility to hide in crevices during the day and then move onto the coral surface during the night to feed. They have many feathery arms, up to 200 (always in multiples of 5). During the day when they are not feeding, their arms are coiled inwards.

Feather Stars are nocturnal filter feeders and they do this by spreading their feeding arms to catch plankton and decaying matter (known as detritus). These, long, slender arms, which are covered in pinnules give the appearance of ornate feathers. When you see them it’s obvious how they get the common name of Feather Stars. They are known as passive suspension feeders because they sit in the prevailing current and wait for food to stick to their feathery pinnules. What they eat is highly dependent on the species, however food items include detritus, some types of plankton, eggs and larvae. The size of their prey is approximately from 0.05 to 0.4mm.

Although looking like they are stuck to the substrate they are in fact highly mobile and will change location, orientation and pinnule extension to increase food capture. They can walk using feet like extensions called cirri, or they move using their arms by alternating the raising and lowering of each arm, which gives the appearance of a rather clumsy and awkward swimming style.

Reproduction takes place in the water where males and females release sperm and eggs. After fertilisation, the eggs will hatch and form larvae. These larvae are free swimming and after several days will settle on the bottom and metamorphise into an adult.