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Species Spotlight: Sea Stars

written by: Niki Fears•edited by: Niki Fears•updated: 5/31/2009

A look at the familiar sea stars, commonly known as starfish.

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    Even those who have not spent a lot of time on the shores of the world or around the ocean are familiar with the iconic sea stars, often called starfish, that have come to be one of the traditional symbols of the beach. In this species spotlight we will get to know the sea stars a little better.

    Appearance and Varieties of Sea Stars:

    Sea stars are a species of animals known as enchinoderms which are invertebrates often categorized by their extruding structures and include starfish, sea urchins, and other similar marine life. They have a central disk from which the structures, or arms, protrude. Generally most sea stars have five of these arms although some specific species of sea stars may have more. Sea stars range in color from dull whitish tan colors to brilliant blues and reds.

    There are several types of sea stars including 1,800 known species including some of the more popular ones such as the blue star fish, crown of thorns sea star, the eleven armed sea star, and of course the common starfish.

    Diet and Anatomy of Sea Stars:

    The digestive system of a sea star contains two stomachs, one called the the cardiac stomach and the referred to as the pyloric stomach. When eating pray, a sea star will invert its cardiac stomach to completely envelope its food source, partially digesting it and then returning back inside of the sea star's body where the food is then passed on to the pyloric stomach to continue the digestion process. Like most animals, further digestion continues in the intestine before the remnants of the food are past on as waste.

    The diet of a sea star is composed mostly of oysters, claims, and some injured or dying fish that may be within its range.

    Reproduction:

    Sea stars can be either female or male and can reproduce both sexually and asexually. Fertilization takes place out side of the sea star's body with body male and female releasing their gametes into the water where they gather and create a fertilized embryo.

    Scientific Classification:

    Kingdom: Animalia

    Phylum: Echinodermata

    Subphylum Asterozoa

    Class: Asteroidea