A sand dollar is a marine invertebrate belonging to the same class as sea urchins and sea stars. While beachcombers often find the bleached, coin-like remains, the living creatures look and feel very different. Sand dollars are not venomous and do not pose a serious threat to humans. However, handling them presents minor risks that vary significantly depending on whether the animal is alive or if you are dealing with its skeletal remains.
Anatomy and Defense Mechanisms
A live sand dollar is covered in thousands of tiny, hair-like spines, giving it a dark, velvety appearance, often in shades of brown, purple, or gray. These short spines are used for movement, allowing the animal to glide across the seafloor and bury itself in the sand for protection and feeding. Unlike sea urchins, the spines are not sharp and do not contain venom, meaning they cannot sting or inject toxins.
The rigid internal skeleton, made of calcium carbonate, is called the “test,” which is the white, sun-bleached object most people find on the shore. The sand dollar’s defense relies primarily on burrowing quickly into the sand to avoid predators. They also possess microscopic, pincer-like structures called pedicellariae, used for cleaning the surface of the test, but these are too small to cause injury to human skin.
Potential Hazards from Live Sand Dollars
Since sand dollars lack venom, a live animal cannot sting or poison a person. The most common physical hazard comes from the friction of their spines, which can cause minor skin irritation, especially with rough handling. In some cases, the tiny, soft spines may break off, causing a faint, temporary burning sensation or minor puncture wounds resembling a pinprick.
A live sand dollar may also release a harmless, yellowish substance called echinochrome when stressed or handled. This compound is not toxic, but it may temporarily stain the skin yellow, which signals that the animal is alive. Given their delicate nature, live sand dollars cannot survive out of the water for long, and handling them can be fatal. For conservation, it is important to leave any dark, fuzzy, or moving sand dollar gently buried in the sand or water where found.
Stepping on a live sand dollar in shallow water is rare, as they usually remain buried beneath the surface. If stepped on, the primary risk is a minor cut from the hard edge of the test or a fragment of the internal skeleton. This mechanical injury is similar to stepping on a sharp shell fragment rather than a biological threat. The mouth, located on the underside, contains a complex chewing apparatus used for grinding food particles, but it cannot bite a person.
Risks Associated with Handling Skeletal Remains
The most common item found on the beach is the dead, smooth, white test, which is generally safe to handle and collect. Once the animal dies, the spines fall off, and the sun bleaches the test white, leaving behind the hard skeleton. The primary risk associated with these skeletal remains is mechanical injury from broken pieces.
A dried sand dollar test is thin and brittle; if shattered by foot traffic or wave action, the fragments can be sharp. Handling a broken, jagged piece or stepping on a fragmented shell can result in minor cuts or scrapes. If you sustain a small cut or puncture from a shell fragment, treat the injury like any other minor abrasion. Clean the wound thoroughly with soap and fresh water to remove lingering particles and monitor the site for signs of infection.