Starfish Characteristics • Invertebrates • Phylum Echinoderm “spiny-skinned” animals • Radically symmetrical - ie a bicycle wheel (usually have 5 arms, or multiples of 5)
Beginning of life of a starfish • starfish begin life microscopic, bilaterally symmetrical, free-swimming larva. • Larva changes and becomes sessile, attaching to the ocean floor • Metamorphosis occurs producing arms and an upper and lower surface
2 types of sea stars (starfish) • 1. Asteroideas – arms connect to one another • 2. Ophiuroideas – arms do not connect to one another
Locomotion • Starfish move using tiny tube feet and the water-vascular system • Water enters a tube, causing them to elongate, and the sucker attached to a surface • Tube foot contracts, water is forced back, starfish moves forward
Reproduction • expel enormous numbers of eggs and sperm into the ocean • fertilization is external. • After fertilization, the tiny, transparent, bilaterally-symmetrical larvae (baby sea stars) travel many miles as they are swept along by ocean currents for about two months. • Larva eat phytoplankton
Diet • carnivores (meat-eaters). • Eat clams , fish, coral, sponges etcother animals. • They push their stomach out through their mouth, releasing digestive enzymes and digest the prey.
Anatomy • do not have a brain; they have a simple ring of nerve cells that moves information around the body. • Eyespots (primitive light sensors) are at the tip of each arm. • If a sea star's arm is cut off, it will regenerate (regrow).