In late summer 2016 we were swimming off Treasure Island’s beach near The Shack and we came across a colossal bed of sand dollars. ¬†Or, as I was later to learn, an urban dwelling of sand dollars that may have stretched for miles (yes miles!) across the sandy ocean floor.
‚ÄčI’ve had a lot of encounters with sand dollars over the years, but this was the first time I had encountered such a huge variety of sand dollar sizes. ¬†Some were half the size of my hand while others were barely as large as the nail on my pinky finger.
This led to a burning desire to know more about how sand dollars live and reproduce. ¬†And that led to putting together this blog post with links to several places where you can learn even more fun facts!
Sand Dollar Basics:
- Sand dollars are echinoderms and closely related to sea stars, sea urchins and sea cucumbers
- They are found in the low intertidal zone to as deep as 30 feet and there are many species living around the world. Other names in other countries include sea cookie and sand cake.
- When sand dollars are found on the beach they are most often already deceased and what you are looking at is their exoskeleton, also called a “test”.
- The shape of a sand dollar makes them excellent at burrowing in the sand. The butt end stays above the sand’s surface to catch food.
- Live sand dollars look very different from their “tests” and they are often green, purple, blue or black with tiny spines and tiny tube feet that they use to get the food to their mouths.
- Sand dollars mainly reproduce by spawning, but they can also clone themselves by breaking off pieces if they think it is necessary. Females release eggs and males release sperm into the water during the spring, which is one reason you find so many sand dollars living together. (It helps with dating and reproduction…)
- Male and female sand dollars are indistinguishable. (And even they don’t really need to know.)
- Sand dollars have a surprising number of predators, including sea gulls, starfish, crabs, otters, snails and octopi. I’d add beachgoers to the list, but I wouldn’t know where to rank them.
- I find them absolutely adorable.
This photo is of a live sand dollar. ¬†You can see the little appendages all around the exterior edges and edges of each opening. ¬†There can be color variations on this muddy brown color. ¬†I’ve seen greens and purples and reds that look as though they’ve been smeared on the top.
Important point here:
This is a live animal, not a trinket. If you want to take home a remembrance from your visit, go to The Florida Shell Shop.
Sand Dollars you find in the shell shops have been treated (sometimes with a glue-based mixture) to strengthen the structure and help stop it from breaking. If you take a live animal home, not only will you kill it but you will likely discard it before arriving home anyway due to messiness and smell, or it will break en route.