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All About Echinoderms & How to Spot Them

The world’s oceans are a treasure trove of biodiversity teeming with life. Creatures with unique traits and appearances inhabit the world’s oceans, from gentle giants like whales to the vibrant corals that form reefs, and the oceans brilliantly showcase just how diverse life on Earth can be.

Among the many forms of marine life, echinoderms stand out as particularly fascinating. These marine invertebrates not only play crucial roles in their ecosystems but also possess intriguing characteristics that make them so interesting.

What is an echinoderm?

Echinoderms belong to the phylum Echinodermata, a group of marine animals known for their distinctive features. Comprising around 7,000 species, echinoderms are exclusively marine and have been a part of Earth’s oceans for approximately 500 million years.

As invertebrates, they lack a backbone but have a unique structure that sets them apart from other sea creatures. Echinoderms are characterised by their radial symmetry, spiny skin, and a calcium carbonate skeleton.

What are some examples of echinoderms?

Starfish

Starfish (Asteroidea) are perhaps the most well-known echinoderms. Belonging to the class Asteroidea, their scientific name varies with different species, such as the common starfish (Asterias rubens).

Starfish are found in oceans worldwide, from the intertidal zone to the deep sea. They are famous for their ability to regenerate lost arms, a trait that not only helps them survive predator attacks but also plays a role in their asexual reproduction.

Starfish are known to be able to grow back a whole starfish from a single limb! Incredible, right?

You can some and see these fascinating creatures for yourself at Hastings Aquarium. We’re home to a number of different starfish species, including the cushion starfish (Asterina gibbosa), green brittle starfish (Ophiarachna incrassata) and the blue finger starfish (Linckia laevigata).

Brittle stars

Brittle stars, belonging to the class Ophiuroidea, are named for their fragile, snake-like arms that can easily break off as a defence mechanism. An example species is the long-armed brittle star (Amphipholis squamata).

These funny-looking creatures inhabit a range of marine environments, often hiding under rocks and in crevices.

Despite their delicate appearance, brittle stars are resilient and can regenerate lost limbs, similar to starfish. They are known for their swift, slithering movements, which help them escape predators and scavenge for food.

Sea cucumbers

Sea cucumbers, members of the class Holothuroidea, have an elongated body that resembles a cucumber, giving them their name.

Sea cucumbers play a crucial role in the marine ecosystem by recycling nutrients through their feeding activities. They ingest sediment, extracting organic matter and expelling cleaner sand.

Some species can even expel their internal organs to deter predators, regenerating them later.

You can see the black sea cucumber (Holothuria forskali) for yourself here at the aquarium!

Sea urchins

Sea urchins, classified under the class Echinoidea, are known for their spiny exteriors and spherical shapes.

The purple sea urchin (Strongylocentrotus purpuratus) is a common example. These echinoderms inhabit rocky seabeds, coral reefs, and kelp forests.

Sea urchins use their spines and tube feet to move and feed on algae, playing a vital role in controlling algal growth in the sea.

 Their spines also serve as a defence mechanism against predators.

If you want to see one with your own eyes, Hastings Aquarium is home to the common sea urchin (Echinus esculentus) and the long spined sea urchin (Diadima setosum)!

How to identify an echinoderm

Echinoderms can be identified by several distinctive characteristics, here are the ways in which you can tell if an animal is an echinoderm.

Marine habitat

Echinoderms are exclusively marine organisms, found in oceans but not in freshwater environments.

Radial symmetry

Most echinoderms exhibit radial symmetry, meaning their body parts are arranged around a central axis.

Spiny skin

Their skin is often spiny or covered with small, calcareous plates, giving them a rough texture.

Calcium carbonate skeleton

Echinoderms have an external skeleton made of calcium carbonate, providing structural support and protection, similar to how an internal skeleton does for mammals.

Water vascular system

They possess a unique water vascular system, which helps in movement, feeding, and respiration through tube feet.

Echinoderms are a testament to the extraordinary diversity and adaptability of life on Earth. From the regenerating arms of starfish to the nutrient-recycling abilities of sea cucumbers, these fascinating creatures play vital roles in their ecosystems.

As we continue to explore and protect our oceans, the study and conservation of echinoderms remains a crucial part of unravelling the mysteries of the sea. Book your tickets to Hastings Aquarium today to come and discover something new about our world’s creatures.

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