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How to Identify Starfish

There are more than 2,000 species of starfish (Asteroidea) that reside in the world's oceans, from shallow tidal flats to deep sea trenches. Also known as sea stars, the animal is part of the phylum Echinodermata family and is related to sea urchins and sea cucumbers. The sea star can range greatly in bodily characteristics, therefore examining the animals distinct features, such as the arms, skin texture, mouth and feet is the best way to identify its family and genus according to the book "Oceanography And Marine Biology, Volume 24," by Margaret Barnes and Harold Barnes.

Instructions

- 1
  Count the arms on the starfish and measure the length of its legs. The star-shaped animal is comprised of a central body and many arms. Most starfish have five arms that vary in length, though there are some genuses that have more. For example, the Feather starfish (Lamprometra palmata) has 10 arms, which measure around 8 inches, while the Sunflower starfish (Oreaster reticulatus) has 22 arms, averaging around 20 to 25 inches, radiating from its body. These arms are regenerative and usually configured symmetrically.
- 2
  Touch the skin of the sea star with bare hands to better ascertain its texture. The skin of a sea star is tough, calcified and covered with prickly spines or knobs, but you can touch it without gloves. Additionally, the colors of the starfish can help identify the genus, and it can range from light tan to deep red. For example, the Cushion starfish (Oreaster reticulatus) has a brownish red body that is covered with golden knobs. The Short Spined starfish (Henricia sanguinolenta) has finer spines and feature many colors, including, yellow, purple and white.
- 3
  Notice the starfish's mouth, which is the circular mark located at the center of its body. The mouth is distinguishable whether or not the echinoderm is eating, and can either be very obvious or subtle depending on the genus. The mouth of the Orange starfish (Fromia monolis) is an orange disk that stands out against the animal's pink legs. The Sugar starfish (Asterias rubens), surrounded by a fine cluster of spines that resemble sugar granules, has a slightly less obvious mouth.
- 4
  Turn the sea star over and examine its feet. These tiny tubes act like hydraulic suctions, helping to move the starfish along at a slow pace. Things to look for are the arrangement of the feet and their length, as they can range from approximately 1/16 to 3/4 inch. The serpent sea star (Orphioderma appressum) has a cluster of feet that can extend up to 1/2 inch away from the star's body, while the feet of the Horned sea star (Protoreaster nodosushas) barely protrude the underbelly's surface and are located in a neat row on the underside of each arm.

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