Crinoidea – Sea Lilies & Feather Stars
Sea Lilies and Feather Stars are a class in the Phylum of the Echinodermata. The Crinoidea contain about 600 species. The scientific name derives from ancient Greek and means lily.
Of more than 5,000 species of the Sea Lilies there are only about 25 living genus. The majority of the recent species are part of the order of the Feather Stars (Comatulida).
The most common species of the Crinoidea are fixed with a stem in the seabed. In the case of Feather Stars, however, this only applies to the juvenile phase, as adult animals they can move free.
The body itself is called Calyx. Off it five arms are leaving, which can be branched several times. So it can be that they have 5, 10 or even 20 arms. These are always feathered.
Habitat and Distribution
Like all echinoderms, Sea Lilies and Feather Stars live exclusively in salt water. Even if there are Crinoidea, which can move and partially “swim”, they are typical soil inhabitants.
Their distribution ranges from the polar caps to the tropical parts of the oceans. They are found in depths down to 6000m.
All crinoids are filterers. With their feathered arms, they filter passing water. To make it more successful, their arms are covered with a sticky mucus.
Feather Stars feed on plankton. The captured prey is fed to the mouth with one of the arms and eaten. In doing so, they have no real stomach, but the food goes directly into a kind of intestine.
Sea Lilies and Feather Stars have separated sexes. They pass eggs and sperm into the open water, where they are fertilized. From the eggs hatches a larva, which sinks to the ground after a few days. Afterwards it undergoes a metamorphosis to the juvenile crinoid. After 10-16 months the young animals are sexually mature and thus also reproductive.
Some species have also been observed to hatch fertilized eggs before they release the larvae into the open water.