Sea Star

Sea Star

Sea stars, also known as starfish, are easily recognized marine creatures. Despite the nickname “starfish,” the sea star is not a fish at all! These star-shaped animals are surprisingly interesting creatures. Read on to learn about the sea star.

Description of the Sea Star

There are over 1,500 different species of sea star, which come in many different shapes and sizes, but all of these animals consist of arms extending from a central disk. In most species, starfish have five arms, giving them a star-shaped appearance. They have spiny skin, and come in many different colors, including shades of red, purple, and yellow.

Interesting Facts About the Sea Star

Sea stars are part of an interesting group of animals. They are incredibly unique in shape, and have interesting mobility and feeding methods. Here are a few fun facts about these fascinating creatures.

  • A Star by Name – All starfish are in the taxonomic class Asteroidea. The class Asteroidea is named in reference to their star, or asteroid, shape. Despite the name, some starfish can have as many as 50 arms!
  • Not-So-Sedentary Lifestyle – Despite their appearance, starfish can actually be quite mobile. Though they move relatively slowly, starfish have a system of tube feet beneath their bodies. These tube feet are used by flowing water into the “tube” and using a suction-cup like foot to grab onto a surface.
  • Sticky Eaters – These tube feet can also be used to aid in feeding. The starfish will wrap its arms around a mollusk, yank the shell open, and spit its stomach out of its own body. The sea star’s stomach wraps around the prey, digests it, and is sucked back into the sea star.
  • Lose a Limb? No Problem! – If a starfish loses one of its arms, it can simply grow another! This process is called “regeneration.” Some sea stars can even reproduce by breaking off one of their legs or splitting in half. The broken leg will simply grow a new sea star, in a process called “fragmentation.”

Habitat of the Sea Star

The 1,500 different species of sea star inhabit many different ocean ecosystems. They can frequently be found in tidepools, coral reefs, kelp forests, mud flats, and the deep sea. This is one marine creature that is not found in any freshwater environment.

Distribution of the Sea Star

Sea stars can be found in any ocean around the world, however, the greatest diversity of species is found in the northern Pacific Ocean.

Diet of the Sea Star

Sea stars feed on clams, sponges, oysters, snails, and other small invertebrates. Some species feed on coral, and some filter feed for small organisms like plankton. Most species expel their stomach out of their body, and the stomach engulfs and digests the prey outside of the body.

Sea Star and Human Interaction

Starfish are commonly dried and sold as novelties in tourist shops. This extensive harvesting of animals has depleted populations of targeted starfish species. Some species have even become endangered in heavily fished ranges.

Domestication

Sea stars have not been domesticated in any way, but some species are successfully kept in aquaria.

Does Sea Star Make a Good Pet

The starfish could potentially make a good aquarium pet, if purchased from captive bred populations. It is important to remember that the care and maintenance of saltwater aquariums is expensive and time consuming. Perhaps traveling to your local aquarium and visiting their touch tank is a better option to get up close with sea stars.

Sea Star Care

Sea stars prefer tanks with plenty of hiding places and substrates to explore. They require extremely stable water quality and salinity, and the water temperature should be maintained very strictly to replicate their natural habitat. Different species of starfish require different diets, so be sure to do your research.

Behavior of the Sea Star

Sea stars are relatively mundane when it comes to behavioral observation. They are slow moving, and spend most of their time searching for food. For the most interesting results, search for time-lapse videos of starfish feeding and interacting.

Reproduction of the Sea Star

The many different species of starfish have different reproductive strategies. Most species have external fertilization, where the eggs and sperm are released into the water to be fertilized. Each starfish arm contains reproductive organs, called “gonads.” These gonads store the gametes, or reproductive cells, which are released during fertilization.

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