If you've ever explored a beach in Maine, you've probably found a sand dollar. But what is a sand dollar? Children have been known to say that sand dollars are pressed sand that has been dried or even the money of mermaids washed-up from the deep. In reality, the fragile disk is the skeleton or "test" of a marine animal. By the time the test washes up on the beach it is missing its velvety covering of minute spines and appears somewhat bleached from the sun. It is hard to believe it was once alive.
Sand dollars are from the class of marine animals known as Echinoids, spiny skinned creatures. Their relations include the sea lily, the sea cucumber, the star fish and the sea urchin. When alive, the local type, Echinarachnius parma is outfitted in a maroon-colored suit of moveable spines that cover the whole shell. Like its close relative the sea urchin, the sand dollar has five sets of holes arranged petal pattern. Tube feet stuck out from these holes and were used for breathing and eating.
Sand dollars live beyond low water on top of or just beneath the surface of sandy or muddy areas. The spines on the somewhat flattened underside of the animal allow it to burrow or to slowly creep through the sand. Fine, hair-like cilia cover the tiny spines. These cilia, in combination with a mucous coating, move food to the mouth opening which is in the center of the star shaped grooves on the bottom of the animal. Its food is plankters (tiny sea creatures) and small particles of plants that end up in the sandy bottom. The five jaws found inside (the doves) crush the food.
Because of their very small edible parts and hard skeleton, few animals bother sand dollars. One animal found to enjoy them on occasion is the thick-lipped, eel-like ocean pout.
On the ocean bottom, sand dollars are frequently found together. This is because they like soft bottom areas and need to find other sand dollars to mate. A sand dollar releases eggs from small openings near the center of the top of the body. The eggs develop into free-swimming larvae which eventually sink to the ocean floor and grow into the adult form.
Since the sand dollar lives in sandy locations,
anyone who would like to collect their shells should comb beaches as the tide is
low. The very best time for collecting is after a heavy storm, as many of the
shells that have died are brought to shore up by the increased wave action.
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