By Katie Wallace
Echinarachnius parma

• Kingdom : Animalia
• Phylum : Echinodermata
• Class : Echinoidea
• Order : Clypeasteroida
• Family : Echinarachniidae
• Genus : Echinarachnius
• Species : parma

• The common sand dollar can be found on the east coast of North America, Siberia and
Japan.
• They live in the sand in intertidal zones.

• They have a “test” that covers the entire sand dollar. The “test” is entirely made up of calcium carbonate.
• They are flat on the bottom and have a slight round curve on the top. They have radial symmetry.
• On the top you can find an outline that is in the shape of a flower (specifically a poinsettia), there are “podia” located here.
• There are tiny grooves on the bottom part of the sand dollar which have “black spines” that trap food.
• “Cilia” near the mouth help to guide food, and prevent the sand dollar from being washed away by currents by burrowing in the sand.
• Sand dollars may or may not have oval-shaped slits that go through the entire body.
• The mouth can be found in the very center of the bottom side of the sand dollar.

• Over time, sea urchins evolved into sand dollars, and went from being shaped like a ball, to flat and round.
• This adaptation was for burrowing purposes.
Sand dollars have what is called a “test”. It surrounds the sand dollar entirely and protects it from the elements. It is made up of very tiny spines and it may also be known as a shell.
There are tiny spikes that stick out on either side of the mouth. They prevent the sand dollar from being swept away by the current in the ocean, and they help it burrow in the sand.

Respiration and movement , and circulation all use the same system, called a “ water vascular system ”, to function. Sea water is pumped into their “tubelike” feet, which are connected to canals that travel throughout the sand dollar. These canals allow the sea water to travel through the body.

• Sand dollars move by contracting muscles in opposite directions
• This forces the sea water from the canals into the tube feet and back into the ocean, causing the sand dollar to lift off the sea floor.
They get into their vertical position for feeding by forcing the water out of one side of the sand dollar, causing half of it to lift, while the other half stays on the seafloor. Once it is completely vertical, it waits for food to come its way.

• Sand dollars have a very simple circulatory system.
• it is also controlled by the “water vascular system”, this means that its powered by the movement of water through the canals.
• Contracting muscles cause the water to continuously move throughout these canals

• Sand dollars reproduce like sea urchins.
• Depending on whether a sand dollar is female or male, it releases its sperm/eggs into the water.
• Not too long after the eggs are fertilized, they become larvae, and float freely in the ocean until they begin the next stage of their life. Larvae are mobile , which means they don’t move themselves, they allow something else to move them.
• The larvae still has a long way to go before it becomes a fully grown sand dollar. There are still many more stages of the lifecycle before the adult stage.