Starfish
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).