The Starfish...Is Not a Fish

large starfish

Scientists would prefer that you call them sea stars, as they are not a fish at all. They are echinoderms (invertebrates, Asteroidea) closely related to sea urchins and sand dollars. They can live up to 35 years and can weigh as much as 11 pounds.

colorful starfish

Sea stars have no brain and no blood, but instead filter salt water through their bodies. With their appealing symmetrical shape, starfish have played a part in literature, legend, design and popular culture. They are sometimes collected as ornaments, used in design or as logos, and in some cultures, despite possible toxicity, they are eaten.

purple sea star

  • There are 2,000 species of sea stars which live in both tropical and cold oceans. (Never fresh water.)
  • They have bony, calcified skin, which may feel prickly or leathery, but which protects them from predators; their often striking colors may scare off potential threats or camouflage them.
  • They are very slow movers, making them easy prey for a wide variety of marine animals including marine birds, crabs, fish, sharks and humans.
  • A sea star’s menu includes mollusks such as clams, oysters, and snails. They have also been known to be cannibalistic. The sea star eats by attaching to prey and extending its stomach out through its mouth to eat and digest its food outside its body, before delivering the partially digested goods to its second stomach inside the body.
  • Sea stars can reproduce sexually and asexually. In sexual reproduction, fertilization occurs in the water with males and females releasing sperm and eggs into the environment. The much less common asexual reproduction occurs as a result of dismemberment that marks the formation of two whole starfish with the same DNA.
  • They can regenerate limbs. It may take up to a year to do so, but they can replicate exactly the limb that was lost or sacrificed, most likely to prey.
  • While the five-armed varieties of sea stars are the most recognizable, some have many more. The common sunstar can have between 8 and 14 arms; other species of sea stars can have 10, 20,  or even 40 arms.
  • Though they do not see much detail, starfish have microscopic eyes at the end of each arm; this enables the starfish to view movement and distinguish between light and dark.
  • Some starfish are lethal. Growing as large as a foot, the Crown of Thorns starfish—named for the poisonous spines that cover its body and arms—is a well-known coral predator, causing serious harm to coral reefs. Other poisonous sea stars include the leather star, the rainbow star, and the sun star, some of which are dangerous to humans.
  • The many arms of the starfish has made its name a popular choice for military assets; the Royal Navy of the UK (made up of 5 arms or branches) named 3 different ships HMS Starfish, in 1894, 1916, and the last in 1933; in WWII, Starfish sites were decoys of lights in the countryside that mimicked lights of cities and drew German bombers away from the real cities; Starfish Prime was a nuclear test conducted by the US high above the Pacific Ocean during the Cold War in 1962.

star fish in the water

This article appeared in the Glassing Magazine March/April 2018 issue.

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