Crinoids are sea creatures related to starfish, brittle stars, and sea urchins. They are often called sea lilies. We know about 700 different species of crinoids.
Some crinoids have a stem, but as they age, others lose their stems. Sea lilies are the crinoids that have limbs, and feather stars are the ones that don’t.
Table of Contents
1. Description of the body
Crinoids have tube-shaped feet, blood vessels that carry water, and radial symmetry. The arms of most crinoids are more than five. Their mouths are on the top, and feeding arms are around them.
The crinoids have a u-shaped stomach. The starfish doesn’t have a way to eliminate waste, but the crinoids do. It’s right next to their mouth.
Crinoids stand straight in the water current and let their stems hang down. With this position, the food grooves can filter out any food moving with the water. Sea lilies live in groups but don’t know what time it is because they live so far down in the ocean.
When not eating, sea lilies make a ball with their arms by folding them around their bodies. Some crinoids only come out at night to eat, so they can’t be seen during the day. But crinoids that eat during the day are easy to see around the reefs of the Indo-Pacific.
Feather stars can crawl and swim. So they can move around and look for food. Also, they can swim away from things like sea urchins that want to eat them.
3. Habitat And Range
During the Paleozoic fossil era, there were a lot of crinoids. Today, they live in the western parts of the Pacific and Atlantic oceans. Crinoids live in deep water and stick to the bottom of the sea. They can live more than 9,000 meters below the water’s surface.
So, people don’t see them very often. Coral reefs are where feather stars live. The feather stars and the sea lilies both live on hard surfaces.
The crinoids have tentacle-like and feathery appendages. The appendages open up like a flower to catch food, like planktons, that get seen inside. Crinoids eat more than just plankton. They also eat foraminifera, diatoms, ciliated protozoans, bits of debris, and some types of eggs.
The crinoids get food from the water currents that move around them. They eat through a system that keeps food in the air.
Crinoids lack true gonads. So, gametes are made in their genital canals, which are inside the pinnules of the crinoid. The sperm and egg are released into the water when the pinnules come together. After the eggs are fertilized, they hatch and let out a larva that can swim on its own.
The females may be able to lay eggs soon after the larvae hatch. If they don’t, they stick to the sea floor after a short time of swimming. After the crinoids have grown up for a while, they break away from the sea floor and swim freely in the ocean.
The crinoid is ready to have babies after 10 to 16 months.