Sand dollars are unique marine creatures often discovered by beachgoers as familiar white, disc-shaped “skeletons,” known as tests. However, a live sand dollar appears quite different from these common finds. Understanding the appearance of a living sand dollar reveals a fascinating aspect of marine life.
Appearance of Live Sand Dollars
A live sand dollar has a distinct appearance, differing from the white tests found on shore. These creatures are dark, often appearing in shades of purplish-brown, reddish-brown, gray, or even charcoal. This coloration helps them blend with the sandy ocean floor where they reside.
Their surface is covered by a dense layer of tiny, hair-like spines, known as cilia, which give them a soft, velvety, or fuzzy texture. These spines are not sharp like a sea urchin’s, but rather flexible and constantly move. This movement aids in their ability to burrow into the sand and move across the seafloor.
Beneath the spines, on their underside, live sand dollars possess tiny, transparent tube feet. These tube feet play multiple roles, including movement, sifting food particles from the water, and drawing oxygen. Their dark hue and velvety covering of moving spines create a specimen visually and texturally distinct from its bleached counterpart.
Identifying Live Sand Dollars
Distinguishing a live sand dollar from a dead one involves observing several key characteristics. The most reliable indicator of life is the movement of its tiny spines. If you gently hold a sand dollar and notice the spines moving, often in a wave-like motion, it confirms the animal is alive.
Live sand dollars also exhibit a dark coloration, ranging from brown to purple, gray, or red, which contrasts with the bleached white of a dead specimen. A fresh, oceanic scent is another sign of a living sand dollar, whereas dead ones may have no smell.
Live sand dollars are firm and intact, unlike the brittle or broken nature of many dead tests. If a live sand dollar is handled, it might secrete a harmless, yellowish substance called echinochrome, which can temporarily stain the skin and serves as another indication of life.
Encountering Live Sand Dollars
When encountering a live sand dollar, handle it with care and respect for the marine ecosystem. Live sand dollars cannot survive for long periods out of water. Taking a live sand dollar from its habitat is illegal in many places due to its ecological importance.
If a live sand dollar is found stranded on the beach, gently return it to shallow, calm water. Minimal contact should be maintained to avoid stressing the animal. Once in the water, it can burrow back into the sand.
Observing these creatures in their natural environment is encouraged. They are an integral part of the marine food web and help filter the sandy seafloor. Allowing them to remain undisturbed ensures they continue to contribute to the health of coastal environments.