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Sand dollars are flattened, round-shaped invertebrates usually found on tropical and temperate beaches in the Northern Hemisphere. They are classified in the order Clypeasteroida, along with sea biscuits, and in the class Echinoidea, along with sea urchins.
See the fact file below for more information on the Sand dollar or alternatively, you can download our 25-page Sand dollar worksheet pack to utilise within the classroom or home environment.
Key Facts & Information
- Other spiny skinned related echinoderms include the starfish and sea cucumber.
- They’re called sand dollars because their skeletons look like silver coins.
- They’re also called sea cookies, pansy shells, sand cakes, cake urchins, and snapper biscuits depending on where they’re located.
- Its skeleton is known as a test. The test is a composition of calcium carbonate plates with a star pattern marked in the middle and a set of pores which reveals its radial symmetry.
- Tests of living, dead, and dying sand dollars are different.
- Living sand dollars have velvety colored spines with tiny hairs on it called cilia. They are usually purple, green, black, reddish brown, gray, or blue, depending on the species. Dead sand dollars are white and hairless. They have hollow tests. They are what we usually find on the beach.
Respiration, Movement, and Diet
- On a sand dollar’s body, there are five paired sets of pores that form a petal-like pattern. These pores extend to tube feet which allow for gas exchange.
- They breathe the using spines found on their upper body.
- These pores also aid in movement. Seawater passes through them and into a sand dollar’s internal water-vascular system which helps in its mobility.
- Sand dollars are also able to move across the ocean floor using the spines on their underside.
- Sand dollars burrow their bodies under the sand when waves are turbulent. They may also develop heavier skeletons in order to stay put.
- Sand dollars transport food to their central mouth using their velvety spines and tiny hairs.
- A sand dollar’s mouth is called “Aristotle’s Lantern” and is located at the bottom of its body. They grind their food using tiny sets of teeth-like structures.
- Their diet consists mostly of food that they can find floating in water. They eat plankton, crustacean larvae, copepods, kelp, algae, and other marine plants.
- It takes up to two days for sand dollars to digest their food.
- Their life span is six to ten years.
Birth, Aging, and Death
- Sand dollars practice sexual reproduction.
- Eggs and sperms are released and fertilized externally in water.
- Fertilized eggs become larvae which feed and move across the ocean using tiny cilia. They eventually settle on the ocean floor after several weeks and then undergo metamorphosis.
- You can tell the age of a sand dollar by counting the number of growth rings on their calcium carbonate plates.
- Sand dollars are not popular to predators because of their tough skeletons. Also, only a small portion of their parts are edible. However, they still have predators: seagulls, crabs, snails, octopuses, the ocean pout, California sheepheads, starry flounders, and sea stars.
- Among the many species of sand dollars, the ones found in the United States are the common sand dollar, the Pacific sand dollar, the sea biscuit, and the keyhole sand dollar.
- The common sand dollar (Echinarachnius parma) is only found in the Northern Hemisphere. It is purplish brown because of its maroon spines, but turns white when brought onto shore. It is typically 3 inches in diameter.
- It lives on ocean floors up to 5,000 feet in depth.
- The Pacific sand dollar (Dendraster excentricus) has many other names. It is also called the eccentric sand dollar, western sand dollar, and biscuit-urchin. It is found in the northeast Pacific Ocean. It’s called “eccentric” because its star pattern is off-center.
- The keyhole sand dollar is named after the keyhole-shaped gap found on its shell. It can be any of the three species that make up the Mellita genus. Mellita tenuis is commonly found in the Caribbean and Florida. Mellita isometra inhabits the east coast of the United States. Mellita quinquiesperforata appears across a wide range of areas, from the South American and Caribbean region like Jamaica and Puerto Rico to Mexico and Costa Rica.
Finding and Preserving Sand Dollars
- Living sand dollars are typically located in shallow waters and sandy areas where they can lie flat and burrow their bodies.
- Dead sand dollars are washed ashore.
- It is best not to pick living sand dollars and leave them be in their natural habitat. Rather collect the bleach-white ones because they’re the dead ones.
- To clean a sand dollar, soak them in fresh water and brush them carefully.
- You can preserve them by making them into jewelry and colored ornaments.
Sand dollar Worksheets
This is a fantastic bundle which includes everything you need to know about sand dollars across 25 in-depth pages. These are ready-to-use Sand dollar worksheets that are perfect for teaching students about the sand dollars which are flattened, round-shaped invertebrates usually found on tropical and temperate beaches in the Northern Hemisphere. They are classified in the order Clypeasteroida, along with sea biscuits, and in the class Echinoidea, along with sea urchins.
Complete List Of Included Worksheets
- Sand Dollar Facts
- All About the Sand Dollar
- Living Dollar Colors
- Vocabulary Check
- Mix and Match
- True or False
- Jumbled Diet
- Sorting Species
- Predator Word Hunt
- From Shore to Store
- Learning Echinoderms
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Link will appear as Sand Dollar Facts & Worksheets: https://kidskonnect.com - KidsKonnect, October 5, 2018
Use With Any Curriculum
These worksheets have been specifically designed for use with any international curriculum. You can use these worksheets as-is, or edit them using Google Slides to make them more specific to your own student ability levels and curriculum standards.