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Starfish Information

Facts About Starfish (Sea Stars)

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Want to learn more about starfish? You've come to the right place. These animals are more scientifically known as sea stars, and you can learn why below. There's also information here about the brittle stars and basket stars. While they are not as familiar as the "true" stars, they are beautiful, colorful and interesting.

10 Facts About Starfish

For starters, starfish are not fish. They don't have gills, scales or tails like fish do, and definitely don't move like fish do (although they do move, sometimes pretty quickly). That's the first of 10 facts about starfish that you'll find here. You can also learn other basics, such as how starfish are classified, how many arms starfish have, how many species of starfish there are, and much more.

Starfish Profile

Did you know that some starfish have 40 arms? This profile of starfish includes information on what starfish look like, how they are classified, how they feed, reproduce and about their unique vascular system, all organized with easy-to-navigate section headings.

Do Starfish Have Eyes?

Sea Star Eye Spots / Jennifer Kennedy
© Jennifer Kennedy

Sure, Patrick on SpongeBob Squarepants has really obvious eyes, but do real starfish? How do starfish see?

It may surprise you to learn that a starfish has an "eye" at the end of each arm. So a starfish with five arms also has five eyes. Although they see well enough to live in their environment, their vision isn't as detailed as ours. Click here to learn more about how starfish see.

Echinoderms

Sea Stars and Sea Urchins / Yuri A. Zuyev, Hydrometeo. Univ. St. Petersburg, NOAA Photo Library
Image courtesy Yuri A. Zuyev, Hydrometeo. Univ., St. Petersburg, NOAA Photo Library

Starfish are echinoderms. This means they are in the Phylum Echinodermata, which contains starfish (sea stars), brittle stars, basket stars, sea urchins, sand dollars, sea lilies, feather stars and sea cucumbers. Overall, this phylum contains over 6,000 species.

Many echinoderms exhibit radial symmetry - their body parts are arranged around a central axis, and they don't have an obvious left and right half - only a top side and bottom side. These organisms also usually have spines, which are less pronounced in sea stars than they are in other organisms, like sea urchins.

Class Asteroidea

Starfish are classified in the Class Asteroidea. All asteroids have several arms arranged around a central disk. Asteroidea are known as the "true stars." These animals are in a separate class from the brittle stars and basket stars, which have a more defined separation between their arms and their central disk.

Class Ophiuroidea

Brittle Star / NOAA
Courtesy NOAA
Ophiuroidea is the group of organisms that contains the basket stars and brittle stars, which aren't considered true sea stars. Click here to learn more about the Class Ophiuroidea.

Brittle Stars and Basket Stars

Basket Star / derekkeats, Flickr
Courtesy derekkeats, Flickr
These fragile-looking animals are classified in the Class Ophiuroidea, separate from the "true stars." However, these animals have a similar body plan to other sea stars, as they have a number of arms arranged around a central disk. The basket and brittle stars have arms that are usually very slender and worm-like, and their central disk is very obvious, in contrast to the true stars.

Photos of Sea Stars

Sea Star Tube Feet / pfly, Flickr
Courtesy pfly, Flickr
Sea stars, basket stars, and brittle stars - here you'll find images of all of these, along with fun facts about each. You can even see some great images of sea star spines and tube feet.

What Is a Madreporite?

Sea Star Madreporite / Jennifer Kennedy
© Jennifer Kennedy, Licensed to About.com
A madreporite is often visible as a light-colored spot on the top of a starfish. This structure is part of the starfish's unique water vascular system.
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