Commonly called 'starfish', sea stars are not fish, but rather invertebrates belonging to a group of animals called echinoderms, which means "spiny skin." They are related to brittle stars, sea urchins, sea cucumbers, and sand dollars. Sea stars come in many colors and sizes, living in all the world's oceans, over 2000 species in all. If you live near a place where sea stars live near the shore, it's relatively easy to set up a salt water tank in your classroom to watch them for a few days.
Sea Star facts:
- Sea stars have no brains and no blood. Their nervous system is spread through their arms and their “blood” is actually filtered sea water.
- The five-arm varieties are the most common, hence their name, but species with 10, 20, and even 40 arms exist.
- Sea stars use suction in the tube feet for movement and feeding. They wrap their bodies around quahogs and other bivalves, using the suction from their tube feet to pull shells apart.
- When the prey is opened, the sea star pushes its stomach out of its body and into the bivalve, secreting enzymes that digest the prey's soft body tissues. The liquefied bivalve is then absorbed into the stomach.
- When a sea star loses an arm, it can grow back.
Sea Star Resources:
- http://animals.nationalgeographic.com/animals/invertebrates/starfish.html National Geographic site about starfish, with photographs, facts, and video-clips.
- http://www.youtube.com/watch?v=uL2Qh4yIzzc You Tube video of a sea star moving on a glass aquarium wall.
- http://library.thinkquest.org/J001418/star.html Excellent Sea Star fact site.
- Starfish (Let's-Read-and-Find... Science) by Edith Thacher Hurd and Robin Brickman, Collins; Revised edition (May 3, 2000) .
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