Category: Sand Dollars

Sand Dollars – Sea Floor Crawlers

Sand dollars are sea creatures belong to the same group as sea urchins and starfish, called Echinodermata.

They are flat, burrowing creatures that live in sandy areas along the coast and are important for the health of oceans.

Where Do Sand Dollars Live?

Sand dollars are found in shallow coastal waters at depths of 2 to 30 feet (0.6 to 9 meters). They prefer sandy or muddy areas where they can bury themselves. They’re also often found in the intertidal zone, some species live in deeper waters up to 90 meters (295 feet).

For example, the Pacific sand dollar lives along the coast from Alaska to Baja California, and the common sand dollar is found on the East Coast of North America.

What Do Sand Dollars Look Like?

Sand dollars have flat, disk-shaped bodies. Their surface shows a flower-like pattern made up of tiny pores, which helps them breathe and move. This hard outer structure is called a test and is made of calcium carbonate, giving them strength and protection.

When alive, sand dollars are usually purple or brown because of their living tissue. After they die, their tissue decays, and their shells turn white. These white shells are often found on beaches.

How Do Sand Dollars Eat?

Sand dollars are filter feeders, meaning they eat tiny bits of food from the sand or water. They feed on microscopic algae, small crustaceans, and organic debris.

Their bodies are covered in tiny spines, which move food toward their mouth in the center of their body. The spines work together with small hair-like structures called cilia to help them eat. Digestion is slow and can take up to two days or 48 hours.

Sand dollars often gather in large groups, sometimes with up to 625 individuals in just one square yard! Being in a group helps them find food and increases their chances of successful reproduction.

How Do Sand Dollars Reproduce?

Sand dollars reproduce by releasing their eggs and sperm into the water during the summer months, usually from July to August. Fertilized eggs grow into larvae that float with ocean currents before settling on the sea floor.

A unique survival trick of sand dollar larvae is that they can clone themselves when they sense danger. By splitting into two smaller larvae, they become harder for predators to find and eat.

It takes about 18 days for fertilized eggs to develop into juveniles. Sand dollars usually reach adulthood and can reproduce after about four years.

How Long Do Sand Dollars Live?

Sand dollars can live for about 6 to 10 years. They bury themselves in the sand to stay safe from predators like fish and sea stars.

Young sand dollars use small tube feet to move through the sand, but as they grow, they rely more on their spines to help them crawl along the sea floor.