What Are Sand Dollars?
Sand dollars are flat, burrowing sea urchins belonging to the order (Clypeasteroida), part of the class (Echinoidea) and (phylum Echinodermata). They are close relatives of sea urchins, heart urchins, starfish, and sea cucumbers. When alive, sand dollars are not the white, smooth objects we find on the beach; instead, they are typically purple, reddish-brown, or brown and covered in tiny spines and fine hairs called cilia. These spines and cilia help them move, capture food, and burrow into sandy or muddy ocean floors. The white, star-shaped tests we collect are their skeletons after death, often bleached by sunlight, resembling old silver coins and giving them their name.
Sand dollars are popular beach finds, with over 150 extant species worldwide, found in intertidal areas from cold Alaskan waters to warm Indonesian seas. Their unique appearance and biology make them fascinating subjects for study and decoration, with a rich history of cultural significance, including the Christian myth of the "Legend of the Sand Dollar."
Sand Dollars Come in Many Varieties According to Location
There are over 150 species, like the Common Sand Dollar (Echinarachnius parma) and Keyhole Sand Dollar (Mellita sp.). Here are some common types of sand dollars:
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Common Sand Dollar (Echinarachnius parma), is found in northern parts of the Atlantic and Pacific oceans. They have a classic round shape, with no holes in test, widely recognized.
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Eccentric Sand Dollar (Dendraster excentricus) also called Western or Pacific sand dollar are found in the Pacific Ocean from Alaska to Baja, California. The anus is off-center.
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Keyhole Sand Dollar (Mellita sp.) are found in the tropical waters in Atlantic, Pacific, and Caribbean Sea. These have distinct keyhole-shaped holes in test, found in shallow waters.
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Caribbean Sand Dollar (Clypeaster rosaceus) these can be found in the Caribbean Sea. They are thicker and also known as inflated sea biscuit.
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Sand Dollar, Sea Biscuit (Clypeaster subdepressus) found in the Atlantic Ocean and Caribbean Sea, from Carolinas to Brazil, These are thicker and found in warmer waters.
Image below shows a Common Sand Dollar
This Stunning mage from EchoesoftheSea.shop shows a Sea Biscuit in all it's glory.
https://www.echoesofthesea.shop/products/cactus-coral-sea-fan-sea-biscuit-glass-print-ocean-decor
Here is an Echoes of the Sea Glass Print that features Keyhole Sand Dollars
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How to Identify Sand Dollars and Distinguish Live from Dead
Live ones are colorful and velvety, moving or buried in sand, while dead ones are white and smooth, often found washed ashore. If unsure turn the sand dollar over, look at it, if you see the little spines moving gently place the sand dollar back in the water. Don’t take live ones—in many coastal areas it is illegal to remove them.
Live vs. Dead Identification:
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Color: Live sand dollars are purple, reddish-brown, or brown; dead ones are white or gray, often bleached by the sun.
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Texture: Live ones have a velvety feel due to spines and cilia; dead ones are smooth and hard.
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Movement: Live sand dollars move slowly or are buried in sand, using tube feet and spines; dead ones are stationary and often found washed ashore.
- Location: Live ones are typically found in shallow water, while dead ones are on the beach.
It’s crucial to leave live sand dollars in their natural habitat, as removing them is illegal in many areas and can harm populations. Dead sand dollars are safe to collect, ensuring sustainability.
Bleaching Your Beach Treasure Finds
For dead sand dollars that haven’t been sun-bleached, you can bleach them at home to achieve the classic white look. The process involves cleaning and treating the test to remove remaining tissue and enhance color.
Here’s a step-by-step guide:
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Soak in Fresh Water: Place the sand dollar in a bucket of fresh water for 1-2 days, changing the water every few hours until it runs clear. This removes sand, debris, and any remaining organic tissue, preventing odor and decay. this process could possibly take longer.
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Prepare Bleach Solution: Mix equal parts household bleach and water (e.g., 1 cup bleach to 1 cup water). For a gentler option, use hydrogen peroxide, which is less harsh and helps maintain the test’s structure. Ensure the container is large enough to hold the sand dollar flat, such as a shallow tray or bowl.
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Soak in Bleach Solution: Submerge the sand dollar in the bleach solution for 10-15 minutes. Do not exceed this time, as prolonged exposure can disintegrate the test. If using hydrogen peroxide, soak for about 30 minutes, as it’s less aggressive.
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Rinse Thoroughly: Rinse the sand dollar under running water to remove all traces of bleach or peroxide, ensuring no residue remains that could damage the test over time.
- Dry Completely: Let it dry in the sun or a warm, dry place for a few days until it’s completely hard and white. Sun-drying also helps harden the test, making it durable for display.
Did You Know?
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The star pattern on top, called the petalidium, is actually their respiratory system, with pores for water and gas exchange, aiding in oxygen intake and waste expulsion.
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On the underside, there’s a mouth surrounded by tiny teeth that grind food, feeding on microscopically sized algae, plankton, and detritus.
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Sand Dollars use spines and tube feet to move slowly across the ocean floor or burrow into sand, using a water vascular system for locomotion and respiration.
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Despite their spiny exterior, sand dollars are preyed upon by sea stars, fish, and crabs, with few predators due to their tough tests.
- Most sand dollars live 6-10 years and can regenerate lost spines, helping them recover from injuries or predation.
How Old is That Sand Dollar You Picked Up on Your Beach Trip?
Counting age rings is similar to counting tree rings, providing insight into their lifespan. Here’s how:
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Examine the Test: Look at the flat surface of the sand dollar’s skeleton (test). You’ll notice faint lines or rings on its surface, each representing a year of growth.
- Count the Rings: Start from the center and count outward. Typically, you’ll find 6-10 rings, corresponding to their 6-10 year lifespan.
Some Creative Ways to Display Your Beach Treasures
Sand dollars are beloved for their natural beauty and make wonderful additions to beach-themed decor. Here are creative ideas for using them:
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Display Bowls: Place them in a glass bowl with sand and shells for a simple yet elegant centerpiece, perfect for coffee tables or shelves. I love these display boxes for your beach treasures. https://www.amazon.com/Juexica-Seashell-Coastal-Treasure-Decoration/dp/B0CT5X71RX/?th=1
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Wreaths: Glue Sand dollars onto wreath forms for a beautiful beachy decoration, ideal for front doors or walls.
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Ornaments: Drill a small hole near the edge and add a ribbon to hang them as ornaments, great for Christmas trees or beach-themed parties.
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Centerpieces: Incorporate them into wedding or party centerpieces for a coastal theme, pairing with candles or driftwood.
- Artistic Touch: Paint or decorate them with glitter, patterns, or inscriptions for a personalized look, enhancing their decorative appeal.
The "Legend of the Sand Dollar"
The five holes are said to represent the five wounds of Christ during the crucifixion. The star pattern on top is believed to symbolize the Star of Bethlehem that guided the wise men. Inside a broken sand dollar, the dried remains of the reproductive organs are sometimes called “doves,” representing peace and the Holy Spirit.
Sand dollars are more than just beach treasures—they’re fascinating marine creatures with diverse species, unique biology, and versatile decorative uses. From identifying live versus dead ones to bleaching them for display, counting their age rings, and exploring myths like the “Legend of the Sand Dollar,” there’s much to discover. Whether you’re a beachcomber, a marine enthusiast, or a decorator, remember to respect these animals by only collecting dead ones and leaving live ones in their habitat. Happy beachcombing!
