Planet Earth Echinoderms Video

This is a clip from the amazing Planet Earth series that aired on the discovery channel. It shows the behavior of some of the echinoderms in the California oceans. You will see starfish, brittle stars, sea urchins, and sand dollars. All of these are members of the echinoderm family. The stop motion photography allows you to see the behavior of these slow moving creatures.

Starfish

Starfish are beautiful and delicate sea creatures. We often find them washed up on the beach. While many see them as colorful decorations, they are actually deadly predators to clams and other mollusks. They eat by turning their stomach inside out. If they lose a leg, they can grow it back... and the leg can grow into a new starfish.

Starfish are Echinoderms, related to sea urchins and sea cucumbers. They come in a wide variety of shapes, sizes, and configurations. All starfish are symmetrical and are composed of arms radiating from the center. While most starfish have 5 arms in the traditional star shape, many species have much more.

Starfish are very slow moving animals and spend most of their time stuck to rocks or scooting along the bottom. They actually move using a network of thousands of tiny tubed feet with a single suction cup at the end of them. They have eyes on the tips of their arms and can only see very basic motion.

While they don't move quickly, they are actually predators that feed on clams, mussels, oysters, and other filter feeding mollusks. They stick their suction cups around the shells and pry them slowly open with steady force. When they have a small opening in the shell, the star fish will turn its stomach inside out and push it into the shell. It then digests the mollusk inside its own shell.


Starfish also have amazing regenerative abilities. If a starfish loses any part of an arm, it will simply grow a new one. As long as the core is intact, a starfish can grow back all its limbs. In some species, each limb can actually grow a whole new starfish. There are many varieties of starfish. I will post about them individually later.