Starfish, Pacific Northwest
The sand dollar is the common name for a marine animal in the same family as the starfish. They have a rigid, flattened, disk with a 5 petal design on the top, made of firmly united plates lying just beneath the thin skin.
Small spines that densely cover the test enable the animal to burrow in the sand just below the surface. Like other members of its class, they are flat and round.
They differ from the closely related sea urchins by their shorter spines and more flattened shape. More convex, short spine sand dollars are called sea biscuits. Sand dollars are abundant on the sandy bottom of deeper waters on both the Atlantic and Pacific coasts. You can find them on any beach in the Pacific Northwest.
They move around by using tube feet, they also move food to the mouth with these tube feet, They can bury themselves in the sand using these feet.
Female sand dollars distribute eggs into the ocean water as males hover nearby. The male sand dollar expels sperm over the eggs to fertilize them. The fertilized eggs float out to sea, develop into larvae and eventually settle at the bottom of the sea where they begin life as baby sand dollars. Sand dollar larvae have the ability to reproduce asexually when threatened in an attempt to protect and propagate their species. Cloned larvae are much smaller in size than their original counterparts, making them difficult for predators to detect. In order for larvae to clone, their environmental conditions must be favorable for growth and reproduction.
Male and female sand dollars are identical with no distinguishable markings to identify their sex. They are quite amazing.