Scientists have identified over 200,000 marine species globally, and among them are some very interesting animals. One major group of marine animals that are unique to the rest are echinoderms (Echinodermata). All the examples of echinoderms on earth consist of living animals that can function without brains.
So, how do they survive and find food? This article will explain what an echinoderm is and provide information on 12 different types of echinoderms.
What is an echinoderm?
Echinoderms are a group of over 7,000 species of marine invertebrates living only in saltwater. As previously mentioned, one of their unique characteristics is they don’t have brains. Instead, they have nerves running through their body from their mouths. Depending on the species, they also have different features for finding food, including eyespots at the end of their arms that detect light or tube feet that smell food.
The name echinoderm is from the Greek term for “spiny skin.” Although not all of them have spiny skin, most have rough textures or spines that are toxic. Other unique characteristics of echinoderms include:
- They can regrow lost limbs or body parts, such as internal organs.
- Echinoderms often feature radial symmetry with body parts of equal sections of five or multiples of five.
- They don’t have blood but use a water vascular system to transport oxygen throughout their body.
- Their skin covers a shell that’s made mostly of calcium carbonate.
12 examples of echinoderms
While you may have heard of some of these echinoderms, here is a list of specific species, including some that may be new to you! Check out the photos and details on their unique features for survival.
1. Spiny Cushion Starfish
Scientific name: Culcita schmideliana
The Spiny Cushion starfish is shaped like a pentagon and inflated, with a puffy cushion-like appearance. They have short, broad arms and a leathery skin surface with spikes. Their colors can range from orange and cream to grayish with pink patches.
You can find these starfish in the tropical waters of the western Indo-Pacific, including inner reef flats and lagoon areas. A unique feature of a starfish is its ability to invert its stomach outward to feed. Meaning it can often eat meals larger than itself.
2. Necklace Sea Star
Scientific name: Fromia monilis
The Necklace sea star is a beautiful species that typically has a marbled body with eye-catching spots in varying sizes and shapes. Its arms also have bright red tips that allow it to ward off predators.
These sea stars live in tropical waters in the Western Pacific and the Indian Ocean, where they prefer depths of up to 164 feet. They use their tube-like feet to eat invertebrates, sponges, and algae.
3. Crown of Thorns Starfish
Scientific name: Acanthaster planci
The Crown of Thorns starfish, also referred to as COTS, can grow up to 3.2 feet in length, making them one of the largest starfish species. They are distinctively covered in protruding spikes that are toxic to humans and marine creatures.
These starfish have an amazing ability to eat living coral colonies by using their flexible bodies and multiple tube feet. They latch onto the reef’s surface and can eat up to 64.5 square feet of reef per year. It’s no surprise that 30 or more COTS in one location can cause devastation to coral reefs.
4. Reticulated Brittle Star
Scientific name: Ophioneries reticulata
The Reticulated brittle star gets its name from the fact that its long starfish-like arms are very fragile. It can easily break if you handle or disturb them. However, like all echinoderms, they can regrow any lost body parts.
You can find these brittle stars throughout the Caribbean, as far south as Brazil and north up to South Carolina and Bermuda. If not in shallow waters, under rocks, or among corals, their distinctive central disc in the middle of their long arms is often found burrowed in the sand.
5. Pacific Sand Dollar
Scientific name: Dendraster excentricus
The Pacific sand dollar, also called sea-cake, western sand dollar, eccentric sand dollar, or biscuit-urchin, is a species of flattened sea urchins. As their name suggests, they look like round coins and burrow into the sandy seafloor. You can often find them near the surf zone along the coast from Alaska to Baja California.
These sand dollars have tube feet that they use for getting oxygen and feeding. Juvenile sand dollars will also use these feet to move around, while adults move by waving their spines. They mainly eat algae or small prey, such as crustacean larva or plankton.
6. Snapper Biscuit
Scientific name: Fellaster zelandiae
The Snapper Biscuit is a species of sand dollar native to New Zealand, also known as the Cake urchin. They typically grow up to 3.9 inches in width.
Like most sand dollars, they have small “hairs” they use to push food into their mouths. They also have jaws with small teeth separated into five sections to help them grind up their food. Sometimes they can chew for up to 15 minutes before swallowing their meal.
7. Flower Urchin
Scientific name: Toxopneustes pileolus
The Flower urchin is also known as the Sea Hedgehog, Toxic sea urchin, or Flower Tip urchin due to the eye-catching and petal-like flowers covering them. But, don’t be fooled by their beauty, they are extremely toxic and their painful stings can pierce through wetsuits and lead to hospitalization.
You can find these sea urchins throughout the Southeast Atlantic and Indo-West Pacific oceans. They are often among the rubble, seagrass beds, or coral reefs, where they eat invertebrates, algae, and decaying organic materials. Their well-developed jaws are adapted to help them grind their prey. These sea urchins are also known to hitch a ride on the backs of crabs when they want to migrate.
8. Keyhole Urchin
Scientific name: Mellita quinquiesperforata
Keyhole urchins are often mistaken as sand dollars since they are flat and circular. However, they are distinctive by the five holes in their body. These urchins are also covered with short spines and generally light brown to sand color. In contrast, sand dollars have no holes and often longer spines and varied colors.
You can find Keyhole urchins in sandy habitats near reefs. They prefer shallow areas and are also common along the beaches of the Caribbeans and Florida.
9. Leopard Sea Cucumber
Scientific name: Bohadschia argus
The Leopard sea cucumber gets its name from its patterns, typically dark eyespots against its paler, leathery skin. You can find them in the Pacific Ocean and the eastern Indian Ocean at depths of 10 to 120 feet.
Like most sea cucumbers, they eat by using their tube feet to find small food items on the seafloor. Their diet consists mostly of waste particles, aquatic invertebrates, and algae. To protect themselves from predators, they can expose skeletal structures with a hook-like feature.
10. Giant Sea Cucumber
Scientific name: Apostichopus californicus
Also known as the California sea cucumber, the Giant sea cucumber is the largest species found along the Pacific Northwest coast from Alaska to Baja California. They can grow between 9.8 and 15.7 inches in length. You can typically find them in low intertidal areas around 290 feet deep, including around rocks, shells, and calm waters.
Like most sea cucumbers, they are “broadcast spawners.” This means to reproduce, females release their eggs into the ocean and males release their sperm. Fertilization occurs externally when the eggs and sperm connect. For successful reproduction, there usually has to be groups of males and females near each other.
11. Stalked Crinoid
Scientific name: Endoxocrinus parrae
The Endoxocrinus parrae is a specific species of Stalked crinoids that can be found in the Indo-West Pacific Ocean and the western Atlantic Ocean at depths of 650 to 3200 feet. They have stalks averaging between 4 to 9 inches in length, with arms that branch out around their mouth.
These crinoids collect food from the water using their arms and eat mostly particulate matter, such as marine snow. When they accidentally catch large or inorganic particles, they will wave their arms to fling the particles away from their mouth.
12. Elegant Feather Star
Scientific name: Tropiometra carinata
Despite its name, the Elegant Feather star is a species of a crinoid typically found along the South African coast. They prefer areas below the level of low tide or at least 167 feet underwater.
These crinoids can grow up to 8 inches in length. They have ten long arms with side branches that look like feathers and are typically a beautiful yellow to brown color. They feed by catching suspended food particles in the water using these arms. If needed, they can also swim with their arms.