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11 Unique Characteristics of Starfish

The starfish is one of the most recognizable creatures in the world. It’s also one of the most extraordinary, with no head, regenerable arms, and a mouth on its underbelly. This article will look at 11 characteristics of starfish as well as some facts about them that may surprise you!

11 Characteristics of starfish

1. Starfish are capable of regenerating their own arms


Having a very simple body structure allows the starfish to regenerate its arms. They have a main central disc with five arms radiating from it. Since these arms have the same structure on all sides, they can regenerate lost limbs easily.

They accomplish this by healing the wound and generating new cells to replace the missing arm portion. So, if a starfish loses or damages one of its arms, it’ll regrow as long as the central disc remains intact. However, this could take a year or more.

2. A starfish has no blood or brain

Without a brain, starfish don’t have the same kind of centralized nervous system that humans do. But they do have a nerve ring around their mouths, which connects to each arm. This network can stimulate the muscles on each of the sea star’s tube feet, causing them to move in whatever direction the animal requires.

And in place of blood vessels, they have a water vascular system that circulates seawater through their bodies to support the proper operation of their organs. This is why, unlike other animals, it doesn’t bleed out if you cut off a starfish’s arm.

3. They’re echinoderms

Starfish and sea urchins in shallow water
Starfish and sea urchins in shallow water | image by mountainamoeba via Flickr | CC BY 2.0

Starfish are echinoderms, and they’re related to sea cucumbers and sea urchins. This means they also have a hard internal skeleton made of calcium carbonate plates. These creatures also have an outer skin that can feel leathery or prickly and protects their bodies while also allowing them to move around.

Starfish have thick skin that helps them defend against predators by making them difficult to eat. The thick skin also aids starfish survival in cold water by keeping them from drying out.

4. Starfish aren’t fish

Starfish aren’t fish, although they’re marine animals with the word “fish” in their names. There are many differences between them, one of which is that they lack gills, scales, and fins to help them survive under the sea.

Starfish are echinoderms with unique body structures and strategies for surviving in the ocean, including tough, spiky skin, a water vascular system, and no backbone despite having an internal skeleton.

5. Not all starfish are star-shaped

Common sunstar
Common sunstar | image by Keith Roper via Flickr | CC BY 2.0

There are several types of starfish in the world. Not all of them are star-shaped, and not all of them have five arms like a star.

Some starfish have seven arms, while others have more than ten, such as the common sunstar, which has 8-14 arms. Another species called wolftrap starfish can also have up to 45 slender arms. There are also starfish that aren’t shaped like stars, such as the cushion starfish, which is round in shape.

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6. Starfish have hundreds of feet

Starfish have tiny feet called tube feet that allow them to move around on the ocean floor. These tiny feet are a muscular extension of their bodies with a suction cup at the tip. They allow the starfish to adhere to rocks or other hard surfaces, as well as move around and catch prey.

These tube feet are connected to a fluid-filled sac that’s linked to the starfish’s water vascular system, which pumps water throughout the starfish’s body.

7. Coral reefs, tide pools, and the deep sea are among their habitats

Starfish underwater
Starfish underwater | image by Bernard Spragg. NZ via Flickr

Starfish are sea creatures that live in the ocean. Only a small number of them are found in brackish waters, but they’re present in every ocean in the world. They’re commonly found on the ocean floor on hard surfaces such as rocks or coral reefs.

These sea stars can also burrow into the sand to hide from predators or to find food. Some starfish require indirect sunlight to survive, so they live near the surface, whereas others can live in extremely deep water with no light at all.

8. Starfish have eyes

Starfish have eyes that can see images and distinguish between light and dark. The starfish’s eye is made up of hundreds of photoreceptors, which are special nerve cells that are sensitive to light. However, their eyes can only see black and white and are located on the ends of their arms, which they use to sense and move around in the water.

This enables the starfish to detect differences in light between the ocean floor and its surroundings, which helps in its search for food and avoidance of predators.

9. Most starfish are carnivorous

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

Starfish are mostly carnivorous that eat other animals to survive. They’re opportunistic animals that eat any mollusks they can find on the sea floor, including clams, snails, mussels, and oysters.

Since starfish lack teeth and jaws, they can’t chew their food like other animals. Digestive juices released from glands in their stomachs when food enters their bodies are used to break down their food.

10. Starfish can ingest their prey by turning their stomach inside out

A starfish’s stomach digests its prey in an unusual way, especially if the prey is large enough to fit in its mouth. Starfish have two stomachs, the cardiac and pyloric. The starfish’s cardiac stomach can be pushed out and engulf a prey.

The digestive enzyme will then be released, breaking down the prey until it’s partially digested. The resulting liquid then flows back into the main body cavity via channels, where it’s absorbed by other organs.

11. Average lifespan of a starfish is 35 years

Starfish, unlike other animals, live longer in the wild. In captivity, they live for 5-10 years, depending on the type of environment that keepers provide, but in the wild, their average lifespan is 35 years, with some living up to 40 years old.

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