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12 Animals With Radial Symmetry

Most animals are bilaterally symmetric, which means their body parts are arranged along two axes: one from head to tail and one from left to right. Radial symmetry is much rarer because it’s the result of specific genetic and developmental conditions.

Although radial symmetry is a rare trait, it doesn’t rule out the existence of certain animals with radial symmetry. This article will discuss some of the extraordinary animals that have this trait.

What is radial symmetry?

Radial symmetry is a type of body symmetry in which an animal’s shape is symmetrical around a central axis, splitting it into two mirror-image halves. This means that if you draw a line through the animal’s middle, you’ll get two identical halves on each side.

12 Animals with radial symmetry

Whether you’re looking for a new pet or want to learn more about nature, these 12 radially symmetrical animals will delight you!

1. Jellyfish

Jellyfish
Jellyfish | Image by tarakko from Pixabay

Scientific Name: Aurelia aurita

A jellyfish is a radially symmetrical marine invertebrate with a gelatinous umbrella-shaped body and tentacles for stinging its prey. These creatures can be found in all seas and oceans, from the surface to the depths.

There are less than 4000 species of jellyfish, each with its own shape and size that distinguishes it from the others. Jellyfish lack a brain, but they do have a sophisticated network of nerves known as a “nerve net” that controls swimming and other behaviors such as feeding and response.

Jellyfish, unlike other animals, lack eyes and ears and rely on sensory organs to find prey and avoid predators instead.

2. Feather stars

Elegant feather star
Elegant feather star | image by Peter Southwood via Wikimedia Commons | CC BY-SA 3.0

Scientific Name: Tropiometra carinata

Feather stars, also known as crinoids, are marine invertebrates that belong to echinoderms. They’re found attached to rocks and coral reefs in warm, shallow waters.

These creatures vary in color from bright orange and yellow to black. The number of arms also varies depending on the species, but most have at least ten arms radiating out from a central disc-like body part. In fact, some species have 80-200 arms!

Feather stars feed on tiny organisms like plankton using their feather-like arms that contain mucous that traps food particles for consumption.

3. Hydra

A two hydra vulgaris under microscope
A two hydra vulgaris under microscope | Image by Ivan Mattioli

Scientific Name: Hydra vulgaris

Hydra is a genus of small aquatic creatures that live in freshwater. They’re radially symmetrical animals with bodies that have the same structure no matter which way they’re viewed. These species have a plump, tubular body with 10 to 12 tentacles for capturing prey.

There are only 25 Hydra species, and the majority of them eat small invertebrates like worms and insects, which they trap with their tentacles. These tentacles are barbed and contain poison, which they use to paralyze their prey before devouring them.

Hydras reproduce by budding as well. They form at the intersection of the stalk and gastric regions and pinch off as new individuals.

4. Sea urchins

Sea urchin with sea pebbles
Sea urchin with sea pebbles

Scientific Name: Echinus esculentus

Sea urchins are invertebrates found on or near the ocean floor. They can be found in all of the world’s oceans, but they prefer shallow, colder waters. Sea urchins lack eyes, but their tube feet allow them to detect light and dark.

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There are approximately 950 different species of sea urchins, and these creatures have radially symmetrical bodies covered in spines. Their size varies by species and can range from an inch to 14 inches, with colors ranging from black to orange, yellow, green, or pink.

5.  Sand dollars

Sand dollar on sand
Sand dollar on sand | image by JackVandenHeuvel

Scientific Name: Echinarachnius parma

The sand dollar, also known as the snapper biscuit, is a small sea creature that lives on the ocean’s sandy or muddy bottom. There are approximately 250 species of sand dollars, all of which are members of the Order Clypeasteroida.

Sand dollars eat algae and small animals that live on or near the ocean floor, such as crustaceans or fish larvae. They have tens or hundreds of tube feet on their bodies that allow them to move around in the water and dig through sediment. These amazing creatures use their spines to catch and collect food particles in their mouths.

6. Sea anemone

Sea anemones
Sea anemones | image by Bernard Spragg. NZ via Flickr

Scientific Name: Stichodactyla tapetum

Sea anemones are a type of sea creature that you can find in all oceans around the world. There are over 1,000 species of sea anemones, with the majority found in tropical coastal waters.

These radially symmetrical creatures have many distinguishing characteristics that set them apart from other animals. They do look similar to flowers, with colorful tentacles that resemble petals.

These animals come in a variety of colors and keep their shapes by contrasting different muscles in their bodies. Sea anemones feed on tiny plankton and fish by capturing them with their stinging tentacles.

7. Fans

Common seafan on a patch reef
Common seafan on a patch reef | image by James St. John via Flickr | CC BY 2.0

Scientific Name: Gorgonia ventalina

Sea fans are a type of soft coral that live in the ocean. They have a single main base that branches out in the shape of a fan. Sea fans can be found in warm waters near the equator, usually in depths of up to 30 meters.

These sea creatures feed on plankton floating in the ocean water, capturing it with their feathery tentacles. These animals can’t move; instead, they anchor themselves to rocks or corals.

8. Sea cucumbers

A sea Cucumber underwater
A sea Cucumber underwater | image by NOAA Ocean Exploration via Flickr | CC BY-SA 2.0

Scientific Name: Thelenota ananas

Sea cucumbers are a type of echinoderm related to starfish and sea urchins. They live in the ocean and come in various shapes and sizes, but the cucumber-like shape is their most common appearance.

They have up to ten tentacles around their mouths, which they use to filter and capture food. These sea creatures eat algae, aquatic invertebrates, and ocean waste particles. Sea cucumbers can reproduce sexually or asexually by budding and releasing eggs into the water to be fertilized by males.

9. Corals

Corals underwater
Corals underwater | image by NOAA via Wikimedia Commons

Scientific Name: Orbicella annularis

Corals are sea creatures that reproduce asexually and live in colonies. They live in shallow tropical waters and attach themselves to rocks or other objects. There are approximately 6,000 coral species, most of which grow in warm waters around the world.

Corals have a lifespan of up to 5,000 years and grow at a rate of 1 to 2 cm per year. Although each coral has its own distinct shape and color, most corals obtain their food from zooplanktons and capture their prey by stretching out their long tentacles.

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10. Sea stars

Seastar eating
Seastar eating | image by NOAA Ocean Exploration via Flickr | CC BY-SA 2.0

Scientific Name: Asterias rubens

One of the most commonly known creatures with radial symmetry is the sea star or starfish. Sea stars are star-shaped marine animals with five arms. They can be found in oceans all over the world, particularly in rocky areas where they feed on mollusks and invertebrates.

Starfish have tube feet and suckers on their arms to pull themselves across the ocean floor, up onto rocks, or onto other surfaces. They also use their tube feet to catch prey and eat their prey by pushing their stomachs out and digesting them outside their bodies.

11. Brittle stars

Brittle star
Brittle star | image by Philippe Bourjon via Wikimedia Commons | CC BY-SA 4.0

Scientific Name: Amphipholis squamata

Brittle stars are sea creatures that look like starfish. They have five arms (some have 9) that they can contract and stretch to crawl around on the ocean floor. These sea creatures can break off their arm when they’re in danger and still grow them back.

There are over 2,000 species of brittle stars in existence. They can be found in the deep sea and range in size from small to large. Brittle stars are omnivores and their diet includes plankton, algae, and plants.

12. Sea pens

Sea pen underwater
Sea pen underwater | image by plovets

Scientific Name: Pennatula phosphorea

Sea pens are a type of colonial marine species found in the ocean that’s made up of many tiny organisms known as polyps. Each polyp resembles a sea anemone with eight tentacles. They look like quill pens when combined and can be found in both shallow and deep ocean waters.

These creatures can grow to be 46 cm tall and live for up to 100 years. Sea pens have the ability to glow in the dark and feed on plankton and dead matter found in the ocean.

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