American Oceans

Sea Lily

Sea lilies are a group of marine animals that belong to the phylum Echinodermata.

a sea lily underwater on a rock

They are also known as stalked crinoids due to their long, slender stalks that anchor them to the ocean floor.

These fascinating creatures have been around for over 400 million years and are considered to be living fossils.

We’ll tell you all there is to know about these amazing sea creatures right down below in this guide!

Anatomy of Sea Lilies

a very colorful sea lily in the ocean

Sea lilies are a type of echinoderm that are commonly found in deep ocean waters. These creatures are known for their unique appearance and interesting anatomy.

In this section, we will discuss the different parts of the sea lily’s anatomy, including the stalk and calyx, arms and pinnules, and cirri and columnals.

Stalk and Calyx

The stalk and calyx are two of the most important parts of the sea lily’s anatomy. The stalk is a long, slender structure that connects the calyx to the ocean floor.

It is made up of a series of plates, known as columnals, which are stacked on top of each other. The calyx, on the other hand, is the bulbous structure at the top of the stalk.

It contains the sea lily’s vital organs, including its digestive system and reproductive organs.

Arms and Pinnules

Sea lilies have five to ten long, slender arms that extend out from the calyx. These arms are covered in small, finger-like structures known as pinnules.

The pinnules are used to capture food particles from the water and transport them to the sea lily’s mouth, which is located at the center of the calyx.

Cirri and Columnals

Cirri are small, hair-like structures that extend out from the columnals of the sea lily’s stalk.

They are used to help the sea lily anchor itself to the ocean floor and to move around.

Columnals are the stacked plates that make up the sea lily’s stalk. They are held together by a series of ligaments, which allow the stalk to bend and flex as the sea lily moves around.

Ecology and Habitat

a bright yellow sea lily

Sea lilies are marine invertebrates that belong to the phylum Echinodermata. They are filter feeders that live in a variety of ocean depths, from shallow waters to deep ocean trenches.

In this section, we will discuss the ecology and habitat of sea lilies, including the ocean depths they inhabit, the ecosystems they are a part of, and the substrate they attach to.

Ocean Depths

Sea lilies can be found in a wide range of ocean depths, from the upper water levels to deep ocean trenches.

They are most commonly found in depths ranging from 100 to 1,000 meters, but some species have been found at depths of up to 9,000 meters.

In general, sea lilies prefer to live in areas with moderate to strong currents, as this helps them filter feed more efficiently.


Sea lilies are an important part of the marine ecosystem. They provide habitat for a variety of other organisms, including small fish and invertebrates.

They are also an important food source for many predators, including sea stars and crabs.

In addition, sea lilies play a role in nutrient cycling, as they filter feed on plankton and other small organisms.


Sea lilies attach themselves to a variety of substrates, including rocks, coral, and other hard surfaces.

They use a stalk to anchor themselves to the substrate, and they can move their arms to capture food particles from the surrounding water.

Some species of sea lilies are also able to detach themselves from the substrate and swim short distances using their arm movements.

Feeding and Metabolism

a black sea lily

Sea lilies are suspension feeders, meaning they trap food particles suspended in the water column using their feathery arms.

They are highly efficient filter feeders, with the ability to capture and consume a wide variety of planktonic organisms such as copepods, krill, and larval fish.

Trapping Food

The arms of sea lilies are covered in small tube feet that function to capture and manipulate food particles.

The tube feet are equipped with tiny sticky pads that allow them to grasp and hold onto food as it passes by.

As the arms move, the food particles are carried towards the mouth, located at the center of the sea lily’s body.

Sea lilies are able to adjust the spacing between their arms to optimize their feeding efficiency.

They can extend their arms to increase the size of their feeding envelope when food is scarce, or contract them to reduce drag when food is abundant.

Additionally, they can adjust the angle of their arms to take advantage of the direction of water currents and maximize their feeding rate.

Rate of Metabolism

Sea lilies have a relatively low rate of metabolism compared to other animals. This is due in part to their sedentary lifestyle and their ability to conserve energy by reducing their activity when food is scarce.

Studies have shown that the metabolic rate of sea lilies is affected by a variety of factors, including light, temperature, and food availability.

For example, sea lilies exposed to bright light have been found to have higher metabolic rates than those kept in the dark. Similarly, sea lilies that are well-fed have higher metabolic rates than those that are starving.

Evolution and Fossil Record

a starfish next to a sea lily underwater

Sea lilies, also known as crinoids, have a long and rich evolutionary history dating back to the Cambrian period, over 500 million years ago.

They are believed to have evolved from cystoids, which were a group of echinoderms that went extinct during the Devonian period.

During the Paleozoic era, sea lilies were one of the most diverse and abundant groups of marine organisms, with many different forms and sizes.

They had long stalks that anchored them to the seafloor, and they used their feather-like arms to filter feed on plankton and detritus.

The fossil record of sea lilies is particularly well-preserved in the Burgess Shale, a fossil deposit in the Canadian Rockies that dates back to the Middle Cambrian period.

Many different species of sea lilies have been identified from this site, providing valuable insights into their morphology and behavior.

However, sea lilies suffered a major decline in diversity during the Permian period, likely due to environmental changes and competition with other organisms. Nevertheless, some species managed to survive and evolve into the modern crinoids we see today.

Triassic to Present

Today, sea lilies are much less diverse than they were in the past, with only a few hundred species known to exist. They are found in all of the world’s oceans, from shallow waters to depths of over 5,000 meters.

One of the most interesting aspects of sea lily evolution is the loss of their stalks in some species. This has led to the evolution of feather stars, which are free-living crinoids that can swim and crawl along the seafloor.

The fossil record of sea lilies has also provided valuable insights into their anatomy and evolution.

For example, the ossicles (small calcified plates) that make up their skeletons have changed in shape and size over time, reflecting changes in their ecology and behavior.

Despite their long history, sea lilies have faced multiple extinction events throughout their evolution.

However, they have managed to survive and adapt to changing environmental conditions, making them a fascinating group to study in the context of evolution and the fossil record.

Classification and Species

sea lily underwater

Sea lilies belong to the phylum Echinodermata, which includes sea urchins, crinoids, feather stars, sea cucumbers, and starfish.

All echinoderms have a unique water vascular system that helps them move, feed, and breathe.

Class Crinoidea

Within the phylum Echinodermata, sea lilies belong to the class Crinoidea. Crinoids are also known as sea lilies or feather stars, and they are characterized by their long, branching arms and a cup-shaped body.

Order Articulata

Sea lilies are further classified into the order Articulata. Articulate crinoids have a segmented stem, which allows them to bend and move.

There are two subclasses of Articulata: Inadunata and Flexibilia.

Species and Specialized Types

There are over 600 species of crinoids, and they are found in both shallow and deep waters.

Sea lilies are a type of crinoid that are anchored to the seafloor by a long stem. Some specialized species of sea lilies have unique adaptations, such as the ability to swim or burrow into the sediment.

Crinoids are classified based on their morphology, including the shape of their arms, the number of arms, and the structure of their stem.

The classification of crinoids is constantly evolving, and new species are still being discovered and described.

Behavior and Movements

a bright yellow sea lily in the ocean

Sea lilies, also known as feather stars, are echinoderms that are found in oceans around the world.

These animals are known for their delicate and intricate appearance, with branching arms that are covered in small, hair-like structures called cilia.

Sea lilies are filter feeders, using their arms to capture plankton and other small organisms from the water.

Sea Lily Movements

Sea lilies have a unique way of moving that is different from other echinoderms. Instead of crawling or swimming, sea lilies use their arms to anchor themselves to the ocean floor.

They can then use their cilia to create water currents that bring food particles towards them. Sea lilies can also adjust the angle of their arms to change the direction of the water currents, allowing them to capture food more efficiently.

Sea lilies can also move their entire body by detaching from the ocean floor and swimming.

They do this by curling their arms up and using them to propel themselves through the water. This behavior is most commonly seen in juvenile sea lilies, which are more mobile than adults.

Predatory and Scavenging Behaviors

While sea lilies are primarily filter feeders, they have been observed exhibiting predatory and scavenging behaviors as well.

Some species of predatory fish, such as the lizardfish, have been observed feeding on sea lilies by biting off their arms. In response, sea lilies can detach their arms as a defense mechanism, which can then regenerate over time.

Sea lilies have also been observed scavenging on the remains of dead organisms on the ocean floor.

They use their arms to collect and filter particles from the sediment, including organic matter from decaying organisms.

Physiology and Life Processes

a sea lily on coral

Sea lilies are unique echinoderms that have a calcium carbonate framework that supports their body.

The rigid framework allows them to remain upright and filter feed in the water column. The stalk of modern sea lilies serves as an important model for the non-linear mechanics of slender structures.

The stalk is composed of numerous plates, which are held together by ligaments that provide flexibility and tensile strength to the structure.

The mechanical properties of the ligaments are variable and under physiological control, allowing the sea lily to adapt to changing environmental conditions.

Energy and Metabolism

Sea lilies are sessile animals that rely on filter feeding to obtain their energy. They use their feather-like arms to capture plankton and other small organisms from the water column.

The captured food is then transported to the mouth by cilia, where it is digested and absorbed. The energy obtained from the food is used to power the various physiological processes in the body.

The metabolism of sea lilies is influenced by water temperature. They are ectothermic animals, meaning that their body temperature is regulated by the surrounding water.

As the water temperature increases, the metabolic rate of the sea lily also increases, allowing it to process food more efficiently.

However, if the water temperature becomes too high, the metabolic rate can become too high, leading to stress and potentially death.

Sea lilies also have a unique life cycle that involves a free-swimming larval stage and a sessile adult stage.

During the larval stage, the sea lily feeds on plankton and other small organisms in the water column.

As it matures, it settles on the seafloor and undergoes a metamorphosis into the sessile adult form.

The adult sea lily then spends the rest of its life attached to the seafloor, filter feeding and reproducing.

Sea Lilies in the Ecosystem

a colorful sea lily underwater

Sea lilies, also known as crinoids, are a type of marine invertebrate that play an important role in the ecosystem.

They are filter feeders that use their feather-like arms to capture plankton and other small organisms from the water column.

By doing so, they help to regulate the population of these organisms, which can have a significant impact on the food chain.

Sea lilies are also important in soft sediment environments, where they help to stabilize the sediment and prevent erosion.

The stalks of sea lilies anchor them to the substrate, while their arms extend upwards to capture food. This creates a complex structure that provides habitat for other marine animals.

Interaction with Other Marine Animals

Sea lilies have a complex relationship with other marine animals. They are often preyed upon by cephalopods, such as squid and octopus, which use their powerful beaks to break through the sea lily’s protective plates.

Sea stars are also known to feed on sea lilies, using their tube feet to pry open the plates and expose the soft tissue inside.

Despite this, sea lilies are also known to form symbiotic relationships with other sea creatures.

For example, some species of shrimp and crabs have been observed living among the arms of sea lilies, using them for protection from predators.

Molecular phylogenetics studies have shown that sea lilies are closely related to sea stars and other echinoderms.

This suggests that they have evolved to fill a specific niche in the marine ecosystem, and that their unique morphology and behavior have allowed them to thrive in a variety of environments.

Frequently Asked Questions

What is the scientific name for sea lilies?

The scientific name for sea lilies is Crinoidea. They are a group of echinoderms that are characterized by their feather-like arms and a stalk that attaches them to a substrate.

How do sea lilies reproduce?

Sea lilies reproduce sexually by releasing eggs and sperm into the water. Fertilization occurs externally, and the resulting larvae drift with the ocean currents until they settle on a suitable substrate and develop into adults.

What is the habitat of sea lilies?

Sea lilies are found in all oceans and at all depths, from shallow waters to the abyssal zone. They prefer hard substrates such as rocks, coral, and shells, where they can attach their stalks and filter feed.

What is the diet of sea lilies?

Sea lilies are filter feeders, meaning they capture small particles of food from the water column using their feather-like arms. They primarily feed on plankton, but they can also consume detritus and small organisms that come into contact with their arms.

What is the lifespan of sea lilies?

The lifespan of sea lilies varies depending on the species and environmental conditions. Some species can live up to 80 years in the wild, while others have a much shorter lifespan.

What is the significance of sea lilies in their ecosystem?

Sea lilies play an important role in their ecosystem by providing habitat and food for other organisms. Their stalks provide a substrate for other animals to attach and grow, while their filter-feeding behavior helps to maintain water quality and nutrient cycling. Additionally, sea lilies are an important component of the fossil record, providing valuable information about past marine environments and evolution.

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