What is a sea biscuit?

A sea biscuit, also known as a sand dollar, is a type of echinoderm that can be found in the shallow coastal waters of temperate and tropical regions around the world. Here are some key points about sea biscuits:

1. Appearance: Sea biscuits are flat, round-shaped marine animals that closely resemble a small, flattened disk or a pancake. They typically measure about 2 to 4 inches in diameter, but some species can grow up to 6 inches.

2. Skeleton: The main body of a sea biscuit is covered with a hard, calcareous skeleton, also known as a test. This skeleton is made up of small plates called ossicles, which are tightly fused together. These plates form a distinctive pattern of five radial rows, resembling a flower.

3. Colors and Patterns: The color of a sea biscuit varies depending on the species and its stage of development. Younger individuals often display vibrant colors like purple, green, or pink, whereas older specimens are usually bleached white by sunlight. They may also have intricate patterns or markings on their surface.

4. Habitat: Sea biscuits are commonly found burrowed in sand or muddy sediments, often in shallow waters up to 100 feet deep. They prefer areas with gentle currents where they can feed and detect prey easily.

5. Feeding: Sea biscuits are filter feeders, using tube feet and spines to capture plankton and other small organic particles suspended in the water. They also have a specialized mouth structure called a petaloid ambulacrum, which helps them gather food efficiently.

6. Movement: Unlike some sea stars that use tube feet to move, sea biscuits use a combination of tiny spines and cilia (hair-like projections) on their underside to slowly and clumsily navigate the seafloor.

7. Reproduction: Sea biscuits have separate sexes, meaning that individuals are either male or female. They reproduce sexually by releasing eggs and sperm into the water column. After fertilization, the larvae develop externally before settling to the seafloor and metamorphosing into young sea biscuits.

8. Symbolism and Collecting: Sea biscuits have held cultural significance in various societies. In some traditions, they are believed to bring good luck and are considered a symbol of prosperity. Collecting sand dollars or sea biscuits is popular among beachcombers, and many people enjoy finding and preserving their skeleton as a souvenir.

Sea biscuits are fascinating creatures that play an important role in marine ecosystems. Their unique shape and delicate patterns make them distinctive subjects of study and admiration.