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A sea lily is not actually a lily, or even a plant. It is a marine animal known as a crinoid, and unlike other types of crinoids, this animal has a stalk that is rooted to the ocean floor. These creatures are aptly named, however, since they resemble lily flowers. They can typically be found at great depths in oceans and seas, and they feed on plankton found in the water. Although they are usually affixed to the ocean floor, these unusual marine animals can uproot themselves to escape from predators.
Crinoids, or Chrinoidea, are a type of echinoderm, which are marine invertebrates that have tube-like feet and somewhat symmetrical bodies. They are members of the Echinodermata phylum, and they are related to starfish and sea urchins. Most crinoids, like sea lilies, were abundant millions of years ago, and they are still around today.
Sea lilies are not flowers or plants, but they resemble a lily flower. Some scientists may even refer to this type of animal as a living fossil. It's close relative, the feather star, is a crinoid as well, but it lacks the long stalk like the sea lily and is free swimming.
The stalk on the bottom of a sea lily will usually grow to about a few feet (0.9 meters) long. It is anchored to the ocean floor most of the time by a suckered foot. Some sea lilies may also have root-like features that allow them to hold on to the ocean floor even better. On top of this stalk is a circular middle, known as a calyx. Several branched and feathery arms grow from the calyx, and these float around in the water surrounding the sea lily.
Millions of years ago, the sea lily was very abundant and could be found in shallow water as well as deep water. Today, however, this animal is typically found in very deep water. It can usually be found in affixed to the floors of the Atlantic Ocean and the Caribbean Sea at depths of around 650 feet (roughly 200 meters) or more.
Plankton and other organic matter is trapped in the floating feather arms of the sea lily, and it is then used as food. This organic matter is then transferred to the mouth located on the top of the calyx, which is known as the tegmen. Sea lilies have no real stomach, so the food is passed through their esophagus straight to the intestines. From there, it travels to the rectum and eventually the anus, which is located on the same surface as the mouth.
Although they are affixed to the ocean floor for most of their lives, sea lilies are capable of movement when necessary. A sea lily will typically move when it needs to escape a predator, such as a sea urchin. When it needs to move, a sea lily will break off a small portion of the bottom of its stalk. By doing this, the animal frees itself from the ocean floor, and it is able to crawl away from danger.
I love learning about deep sea creatures like the sea lily. It seems like so man of them mimic one type of living creature while actually being another. The sea lily certainly looks like it could be a plant, but it's not.