We recently entertained and educated you with a blog describing the echinoderm known as Asteroidea, also known as the starfish, which has been beautifully captured in our custom, handmade art pieces. Well, Getting Nauti suggests that you might find the starfish’s cousin equally fascinating. Oh, and undoubtedly find our rendition of this amazing creature to be worth adding it to your collection.
Which cousin, you ask?
Well the Echinarachnius known as parma, which is in the Clypeasteroida order of burrowing sea urchins more commonly known as sand dollars (but includes the somewhat wider sea biscuit). No doubt you’ve found a sand dollar or two while beach combing. And if not, then you’re probably too busy checking out other potential beach beauties, like say maybe the type sporting either bikinis or jammers.
Sand Dollar on the Beach
Anyhow, that sand dollar you found on the beach (or crunched underfoot while ogling a different beach beauty) was likely dead, which means you were pretty much holding a skeleton and not the live creature. But that skeleton, with its five-fold radial pattern that looks like a poinsettia, is a work of art, and some folks believe that finding a sand dollar brings on the good luck.
Like its starfish cousin, the sand dollar’s five-sectioned body plan emanates from a central disk. But unlike the starfish, and because of its rigid endoskeleton, the sand dollar cannot just lose one of its sections to evade predators. Fortunately, a mature sand dollar has few predators, and thus little need to let loose body parts as an escape mechanism. And one of its few predators is the sunflower sea star, which can sport up to 40 arms, so no real chance of escape there no matter how many body parts shed.
Sunflower Sea Star
Live sand dollars look very similar to that cherished dead skeleton that becomes beach art, but are not the grey or white color of their bleached skeletons, but come in a variety of colors such as green, blue, violet or purple. Other than the color the only noticeable difference is that live sand dollars sport a thin skin of velvet-textured spines that are covered with tiny cilia (hairs), which act as the sand dollar’s propulsion system, among other features.
Sand Dollar Cilia on Display
Yeah, not only do those fuzzy spines and sub-hairs act as tiny feet to move the sand dollar or help it burrow into the sand, but the spines also serve as its gills and the spines and cilia help move food to its mouth. We’re talking multipurpose here!
Prior to becoming fodder for beach combers, sand dollars spend their lives anywhere from the intertidal zone to deep water in both the temperate and tropical zones of the world’s oceans. They don’t do a whole lot but eat, have sex, move around a bit, burrow, and stand on end.
You Can Almost Hear Barry White Playing in the Background...
Eating consists of random crustacean larva, algae and small bits of dead organic material that get caught in its cilia, that then moves those tasty stray food items down to the mouth, which is located in the middle of the underside part of its body. As that small mouth only has the equivalent of five teeth, the sand dollar can take up to 15 minutes to chew on a tasty morsel before it can swallow.
Sand dollar sex is equally exiting, with both sexes releasing their respective gametes into the water that then merge to become larvae.. Also of interest is that scientists recently discovered that the larvae clone themselves when exposed to fish mucus, probably as a means of increasing their numbers with the threat of predation.
Sand dollars burrow as a means of hiding from their few predators, and to anchor themselves to the sea bed in the face of currents and/or tidal action and waves. Juvenile sand dollars eat sand to give themselves added weight as a means of preventing themselves from getting whisked away by currents or tides. In the absence of tides and currents, sand dollars like to stand on their rounded edges, perhaps to expose their hairy bodies to more potential food bits.
Sand Dollars Standing on Edge
So, there you go—now you know all about sand dollars. And next time you go beach combing and don’t find one, you’re probably just a day late and a dollar short. But you can bet your bottom dollar that you’ll find one eventually. Or you can just order one of Getting Nauti’s hand-crafted pewter sand dollars and save yourself the trouble. Plus, dollar for dollar the pewter one is definitely going to last far longer than that bleached bit of bone-like shell.