Range: Temperate and tropical marine waters worldwide Habitat: Shallow coastal waters Size: 3 inches (7.62cm) in diameter or more Diet: Eggs, algae, larvae, small crustaceans, and more Threats: Pink sea stars, starry flounders, sheepheads, and pout Life span: Up to ten years

Transcript:

Today on Animal Fact Files we’re talking about sand dollars. There are plenty more animals you can learn about by subscribing! Thank you to M. G. M. gaming for today’s suggestion. No, they’re not the currency used by undersea life forms, but they were named after currency! Sand dollars, who are sometimes known as sand cakes, sea cookies, and sea biscuits are echinoderms and are related to sea stars and sea urchins. Sand dollars received their common name because when washed up on shore and bleached by the sun, their round bodies turn a silvery white, giving them an appearance much like a silver dollar coin. But this iconic white imagery is actually that of a sand dollar’s skeleton.

In life, sand dollars appear in deep browns or dark purples and they’re covered in short spines. These spines are important for many aspects of the sand dollar’s life. The spines help a sand dollar move across the bottom of the ocean and burrow into the sand. Sand dollars tend to live along the coast usually no more than 100 feet (30.48m) below the surface, though some individuals have been found nearly 1,000 feet (304.8m) down. They typically inhabit sandy areas with generally good water currents that help them access food.

The food they collect consists of eggs, algae, larvae, small crustaceans, and more and is moved to the sand dollar’s mouth via those aforementioned spines. A sand dollar’s mouth is located on its under, or ventral, side in the center of its body. No, the mouth isn’t the holes found in some species, and, surprisingly for an echinoderm, it’s mouth doesn’t double as it’s anus - sand dollars have an anus separate from their mouths.

A sand dollar’s mouth houses an organ called Aristotle's lantern - which is basically a jaw with five particle crushing teeth. If you’ve ever held a deceased sand dollar and shaken it up at bit, you may have heard something rattling around inside. More than likely, you’re hearing the Aristotle’s lantern of that sand dollar. This mouthpiece is used for “chewing” a sand dollar’s meal which can take nearly two days to digest.

A hard body might seem an unappealing meal for most animals, but some species, such as pink sea stars, starry flounders, sheepheads, and pout enjoy the crunch a sand dollar has to offer. Eesh. I’m having flashbacks to the coral-eating parrotfish episode.

When searching for sand dollars, people often seek the star pattern found along the top of a sand dollar’s test. In life, this pattern is more difficult to see through all the spines. This section of a sand dollar is actually where their gills are located, and its the spines found here that act as gills. Told you those spines come in handy for sand dollars!

Sand dollars can be found on just about every continent (looking at you Antarctica) in temperate and tropical waters. They breed through external fertilization meaning males and females release sperm and eggs into the water column where they are then fertilized. The eggs can hatch within a few hours and the larvae develop over the course of a few weeks floating in the water column. When they begin forming their hard skeleton, they skin the bottom. Sand dollars can live to be ten years old! At full size a sand dollar may be more than three inches (7.62cm) across, but some have even been reported to have a more than five inch (12.7cm) diameter.

And we’ll leave you with this neat fact: if you’re ever uncertain whether a sand dollar is alive or dead, hold it in the palm of your hand. A live sand dollar will likely turn your skin yellow and that’s a dead giveaway to put that sucker back in the water. Isn’t nature awesome?

For more facts on sand dollars, check out the links in the description. Have you ever seen a living sand dollar in person? Tell us about it in the comments! Give a thumbs up for animals, and thank you for watching Animal Fact Files!