Hobbies And Interests
Body
Starfish are biologically classified as Asteroidea within the echinoderm group. They have no identifiable front or back, as their body is characterized by radial symmetry. They have a bony, textured surface consisting of hundreds of tiny legs that can move in any direction without turning. A unique hydraulic system replaces the need for muscular locomotion or blood. They can regenerate major limbs, spines and intestines. Their outer layer also has structures called pedicellaria that keep them free from algae.
Variations
Different species of starfish display diverse and sometimes dramatic variations. Spiny cushion starfish have a plump, bulbous shape like a pillow. These starfish are usually deep red in color. Aquamarine-colored crown-of-thorns starfish are covered with spiny, venomous arms and can grow as wide as 20 inches. Necklace sea stars have long slender radial arms with red and white bumps, while Egyptian sea stars have a deep brick red color covered with white bumps.
Behavior
Many starfish are predators that eat mollusks or barnacles. Crown-of-thorns starfish graze among coral reefs eating coral polyps. Some species eat by protruding their stomachs over their prey, thus saturating the prey in digestive fluids.
Starfish reproduce by projecting sperm and eggs into the water. In some cases, they can reproduce asexually by splitting in half to form two new creatures. This capacity, along with regeneration, is possible because most of their vital organs are inside of the arms, and only some organs depend on the central body to function.
Environment and Predators
Starfish live exclusively in saltwater, albeit all kinds. They survive everywhere from cold, deep ocean trenches to warm, tropical shores. Some species live solely in sand while others live in widely varied terrain such as rubble and coral reefs. Their predators include triton trumpets, harlequin shrimp and reef crabs. They have symbiotic relationships with many other species including shrimp, crabs, snails and fish.