Sand dollars are commonly recognized by the bleached, white, disc-shaped skeletons often found on beaches. These familiar objects, however, are the remnants of a marine creature. Many people are unaware of what a sand dollar looks like when it is alive in its underwater habitat. This article reveals the reality of these animals in their living form.
The Vibrant Reality: Appearance of Live Sand Dollars
A living sand dollar presents a contrast to the familiar white skeleton. These marine animals are typically dark, appearing in shades of purple, reddish-brown, or dark grey. This darker hue helps them blend into their sandy surroundings.
The surface of a live sand dollar feels velvety or fuzzy, a texture due to the thousands of tiny, hair-like spines that cover its body. These short, dense spines are not just for appearance; they are constantly in motion, assisting the sand dollar with burrowing into the sand and moving across the seafloor. Some of these spines also function as gills for respiration.
On the underside of the sand dollar, numerous translucent tube feet. These delicate structures extend and retract, serving multiple functions including feeding and respiration. They also contribute to the animal’s slow, deliberate movement.
Life Beneath the Sand: Habitat and Behavior
Live sand dollars inhabit shallow, sandy ocean floors in temperate and tropical waters. They often gather in large groups, forming dense beds across the seafloor. This communal living can support as many as 625 individuals per square yard.
Sand dollars can partially or fully bury themselves in the sand. They use their specialized spines and muscles to push their front edge into the substrate at a slight angle, embedding their bodies. This burrowing can provide protection from predators and strong currents.
Sand dollars are suspension feeders, using their cilia and tube feet to capture microscopic food particles. They filter plankton, detritus, algae, and bacteria, moving these particles along their body to a central mouth located on their underside. Their slow movement, often just a few centimeters per hour, allows them to effectively forage in their sandy environment.
Respecting Marine Life: What to Do If You Find One
Identifying a live sand dollar involves observing several cues. If gently touched, the spines may show subtle movement. Some live sand dollars may also leave a yellowish stain on the skin, a harmless substance called echinochrome.
It is important to leave live sand dollars undisturbed in their natural habitat. These animals play a role in the marine ecosystem, and removing them can negatively impact the ecosystem. Collecting live sand dollars is also illegal in many coastal areas.
If a live sand dollar is found out of water, it should be returned gently to the water. Place the sand dollar in shallow water, ensuring it is right-side up, to re-orient and burrow back into the sand. This simple action helps ensure the animal’s survival and supports marine conservation efforts.