The sand dollar: everything need to know
March 3, 2022
While star-stamping on sand dollars’ bones is a popular beach discovery, few people realise what the bottom-dwelling crustaceans are like while they’re alive. The truth is that they look almost nothing like what you see on the beach at high tide. In other parts of the world, the sand dollar, also known as a “sea biscuit” or “sand cake,” is purple and hairy at its height. It is a member of the order clypeastroida and is found across the northern hemisphere’s tropical and temperate oceans. From their different nicknames to the unique way they eat, here are facts about sand dollar shell you may not be aware of.
While living, sand dollars happen to be not white
The majority of people become aware of sand dollars only after they have died. The white “shells” found along the beach are their bones; while the marine species is alive, it may vary in colour from a deep reddish-brown to a vivid purple. In contrast to their porcelain-like smooth skeletons, living sand dollars happen to be covered in flexible bristles called spines that conceal their star pattern. As it dies, the light bleaches the skeleton (the “test”), turning it white, and the little spines fade away.
Sand dollars cannot survive in the absence of water for an extended period of time
While removing live sand dollars from the beach is illegal in the majority of countries, legislation regarding deceased species vary. It is recommended that you never pick up a sand dollar shell if you are unsure whether it is alive or dead. They can only survive out of the water for a few minutes while alive. Sand dollars breathe via their characteristic “petals,” properly known as petaloid, which are a series of holes through which tube-like, breathing feet emerge.
They have a relationship with sea stars and sea urchins
Sand dollars happen to be burrowing invertebrates that belong to the spiny-skinned creatures or echinoids, a family of marine animals. They are sometimes referred to as “irregular” sea urchins and share a great deal of their anatomy with their spherical relatives. They are also related to other radially symmetrical species such as sea cucumbers, sea lilies, and sea stars (referred to as starfish), however, the latter is classified separately.