Starfish Facts
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Starfish or Sea Stars, the common name given to an entire class of ocean animals called Asteroidea, or Asteroides for short, inhabit the world's ocean floors.
While the name starfish often brings to mind a five armed animal such as the purple orchre star (Pisaster ochraceus), at the top of the page, it is not the starfish's defining characteristic.
Rather, true starfish are characterized as having a symmetrical body with arms extending from the center. While five armed starfish are common, the two thousand or so different starfish species can have anywhere from four to fifty arms. The sunflower star, for example, a common West Coast starfish, has twenty four arms.
Bat stars (Asterina miniata) present themselves as another variation on the symmetry theme, this time with webbing between the arms.
They live among the rocky and sandy shores along the Pacific coast from Alaska to Southern California, often close to kelp and grassy areas, its food source of choice.
The second picture shows a bat star specimen with five arms. However, bat star species assume a variety of colors and can grow anywhere from four to nine arms.
All starfish species tend to move slowly along the ocean floor using the many tube feet situated along the bottom of their bodies. The suction cups attached to the ends of each tube allow them to stay firmly planted in place.
Like all animals, most starfish movement is geared toward a search for food, with mollusks such as barnacles, clams, mussels and snails often their food of choice. Their mouth is located on the bottom of the body, which makes it easy to consume their prey once they can attach their body on top of it.
Living in the ocean can be dangerous for any animal, and although the starfish is a predator, it can also be prey for larger starfish, crabs, fish, birds and sharks. The third picture shows a gull in the process of consuming one.
In instances where they are prey, being slow moving has its drawbacks. To compensate for their slow movement, starfish have evolved with an ability to regrow a limb that is lost to a predator.
Most peoples' familiarity with starfish comes from the species found close to shore. Near shore starfish normally inhabit the middle and low littoral zones (the areas furthest from the high tide mark on the shoreline).
Low tides can also cause stress for starfish, because it creates a situation where they can be exposed to the air, and their bodies are not designed to be out of the water for extended periods of time.
Sea stars are not considered endangered, however, like other marine life, their existence depends on healthy oceans.
Recent reports about coastal dead zones along the West Coast, ocean areas that lack oxygen, also include reports of dead sea stars.
© 2007-2011. Patricia A. Michaels