Starfish, Pacific Northwest
The Starfish are made up of of over 6000 marine species of sea urchins, feather stars, sea stars, brittle stars, sand dollars and sea cucumbers. There are around 180 species of these animals that live in the waters along the Pacific Northwest. Look in any tidal pool and you will see many types of these fascinating creatures.
Although they come in many forms and body shapes, they all have a radial symmetry and a five part symmetry and they all have tube feet or tubular appendages.
Echinoderms like sea urchins and sea stars play a very important role in the ecology of the ocean shore by controlling the quantity and quality of seashore plants and creatures with their ferocious appetites.
Some of them will only eat live animals while some will eat both live and dead creatures, helping to keep the shores clean and some others only eat plant life.
The predator most feared by echinoderms are the sea stars themselves, but birds, otters and humans all feed to a lesser degree on them.
They can reproduce in more than one way. Starfish can either spawn together, or they can asexually reproduce, though this isn’t the ideal way to produce new starfish because it doesn’t promote genetic diversity within the species. While sexual reproduction is a naturally occurring process, asexual reproduction for starfish is usually only the result of dismemberment that results in the formation of two new starfish whom both have the same DNA.
They usually reproduce sexually by spawning. Spawning means that the sex cells are released into the water. They will gather in groups to reproduce, which increases the likelihood the sperm and eggs will find each other. They have sexual organs in each arm. During a breeding season the males organs fill with sperm and the females fill with eggs. When starfish spawn, the males release sperm and the females release eggs in great numbers. Female starfish may release millions of tiny eggs into the water during a spawning session.