Range: Deep marine waters worldwide Habitat: Ocean floor substrate Size: 2 inches - 1 foot (5-30.5cm) long arms Threats: Fish Life span: Unknown

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Today on Animal Fact Files we’re discussing crinoids. These animals are echinoderms meaning they’re related to sea urchins and sea stars. Crinoids are also known as sea lilies and feather stars. They have two different common names to represent their two different body types. Crinoids were once much more abundant, especially during the paleozoic era. There are 5,000 known species from prehistoric times, but today there are approximately 600 living species, and they’re considered generally rare in comparison to their previous distribution. One type, commonly known as the sea lily, really does look like a flower underwater.

Sea lilies have a stalk that attaches to substrate on the ocean floor and is topped with branching arms that could be said look somewhat like flower petals. This body structure was more common in prehistoric times and the plates making up the stalk were most commonly preserved in fossil form, though sometimes full individuals are found! Today, these are found in deep marine waters throughout the world.

The other body structure, commonly known as the feather star, foregoes the stalk and simply has the flower section and small root-like feet that can hold tight to substrate. These forms move about and some even swim by undulating their bodies! Feather stars are more abundant in shallow water reef areas and make up a majority of the living species of crinoids.

Both body types eat by filter feeding. The flower petals have tube feet which are covered in sticky mucus. These gather food and pass it towards the animal’s mouth, located in the middle of the flower petal like structures. Food for crinoids includes planktonic plants and animals as well as floating detritus. Unlike sponges, crinoids don’t produce any kind of current to collect this food and instead rely on the currents of the surrounding waters. Feather stars may move to better vantage points to gather more food at different times of the day, with some observed preferring to stay hidden in reef crevices until night. While some species have arms that reach only 2 inches (5cm) in length, others may be more than a foot (30.5cm) long.

Like sea stars, crinoids can regrow lost body parts, so if their delicate, sticky arms are removed by predatory fish or other animals, they will be regenerated. Parasites may enter the digestive system of crinoids and eat the food the crinoids collect before the crinoids themselves are able to digest the food. Sea urchins may also attack and eat their stems.

Crinoids are distincly either male or female like sea urchins, and their reproductive organs are typically located in their limbs. Eggs and sperm are released into the water where they’ll be fertilized, though some species, especially the deep water sea lilies, brood their eggs in specialized sacs on their arms. Free-swimming larvae hatch from eggs and settle to the bottom after a few days. They develop a stalk and mature until they become adults. In feather stars these adults break away from the stem. We weren’t able to find how long these animals live, however, evidence suggests they and their ancestors have been living on our planet for at least 480 million years!

For more facts on crinoids, check out the links in the description. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files!